| 1 | =head1 NAME |
| 2 | |
| 3 | perl561delta - what's new for perl v5.6.x |
| 4 | |
| 5 | =head1 DESCRIPTION |
| 6 | |
| 7 | This document describes differences between the 5.005 release and the 5.6.1 |
| 8 | release. |
| 9 | |
| 10 | =head1 Summary of changes between 5.6.0 and 5.6.1 |
| 11 | |
| 12 | This section contains a summary of the changes between the 5.6.0 release |
| 13 | and the 5.6.1 release. More details about the changes mentioned here |
| 14 | may be found in the F<Changes> files that accompany the Perl source |
| 15 | distribution. See L<perlhack> for pointers to online resources where you |
| 16 | can inspect the individual patches described by these changes. |
| 17 | |
| 18 | =head2 Security Issues |
| 19 | |
| 20 | suidperl will not run /bin/mail anymore, because some platforms have |
| 21 | a /bin/mail that is vulnerable to buffer overflow attacks. |
| 22 | |
| 23 | Note that suidperl is neither built nor installed by default in |
| 24 | any recent version of perl. Use of suidperl is highly discouraged. |
| 25 | If you think you need it, try alternatives such as sudo first. |
| 26 | See http://www.courtesan.com/sudo/ . |
| 27 | |
| 28 | =head2 Core bug fixes |
| 29 | |
| 30 | This is not an exhaustive list. It is intended to cover only the |
| 31 | significant user-visible changes. |
| 32 | |
| 33 | =over |
| 34 | |
| 35 | =item C<UNIVERSAL::isa()> |
| 36 | |
| 37 | A bug in the caching mechanism used by C<UNIVERSAL::isa()> that affected |
| 38 | base.pm has been fixed. The bug has existed since the 5.005 releases, |
| 39 | but wasn't tickled by base.pm in those releases. |
| 40 | |
| 41 | =item Memory leaks |
| 42 | |
| 43 | Various cases of memory leaks and attempts to access uninitialized memory |
| 44 | have been cured. See L</"Known Problems"> below for further issues. |
| 45 | |
| 46 | =item Numeric conversions |
| 47 | |
| 48 | Numeric conversions did not recognize changes in the string value |
| 49 | properly in certain circumstances. |
| 50 | |
| 51 | In other situations, large unsigned numbers (those above 2**31) could |
| 52 | sometimes lose their unsignedness, causing bogus results in arithmetic |
| 53 | operations. |
| 54 | |
| 55 | Integer modulus on large unsigned integers sometimes returned |
| 56 | incorrect values. |
| 57 | |
| 58 | Perl 5.6.0 generated "not a number" warnings on certain conversions where |
| 59 | previous versions didn't. |
| 60 | |
| 61 | These problems have all been rectified. |
| 62 | |
| 63 | Infinity is now recognized as a number. |
| 64 | |
| 65 | =item qw(a\\b) |
| 66 | |
| 67 | In Perl 5.6.0, qw(a\\b) produced a string with two backslashes instead |
| 68 | of one, in a departure from the behavior in previous versions. The |
| 69 | older behavior has been reinstated. |
| 70 | |
| 71 | =item caller() |
| 72 | |
| 73 | caller() could cause core dumps in certain situations. Carp was sometimes |
| 74 | affected by this problem. |
| 75 | |
| 76 | =item Bugs in regular expressions |
| 77 | |
| 78 | Pattern matches on overloaded values are now handled correctly. |
| 79 | |
| 80 | Perl 5.6.0 parsed m/\x{ab}/ incorrectly, leading to spurious warnings. |
| 81 | This has been corrected. |
| 82 | |
| 83 | The RE engine found in Perl 5.6.0 accidentally pessimised certain kinds |
| 84 | of simple pattern matches. These are now handled better. |
| 85 | |
| 86 | Regular expression debug output (whether through C<use re 'debug'> |
| 87 | or via C<-Dr>) now looks better. |
| 88 | |
| 89 | Multi-line matches like C<"a\nxb\n" =~ /(?!\A)x/m> were flawed. The |
| 90 | bug has been fixed. |
| 91 | |
| 92 | Use of $& could trigger a core dump under some situations. This |
| 93 | is now avoided. |
| 94 | |
| 95 | Match variables $1 et al., weren't being unset when a pattern match |
| 96 | was backtracking, and the anomaly showed up inside C</...(?{ ... }).../> |
| 97 | etc. These variables are now tracked correctly. |
| 98 | |
| 99 | pos() did not return the correct value within s///ge in earlier |
| 100 | versions. This is now handled correctly. |
| 101 | |
| 102 | =item "slurp" mode |
| 103 | |
| 104 | readline() on files opened in "slurp" mode could return an extra "" at |
| 105 | the end in certain situations. This has been corrected. |
| 106 | |
| 107 | =item Autovivification of symbolic references to special variables |
| 108 | |
| 109 | Autovivification of symbolic references of special variables described |
| 110 | in L<perlvar> (as in C<${$num}>) was accidentally disabled. This works |
| 111 | again now. |
| 112 | |
| 113 | =item Lexical warnings |
| 114 | |
| 115 | Lexical warnings now propagate correctly into C<eval "...">. |
| 116 | |
| 117 | C<use warnings qw(FATAL all)> did not work as intended. This has been |
| 118 | corrected. |
| 119 | |
| 120 | Lexical warnings could leak into other scopes in some situations. |
| 121 | This is now fixed. |
| 122 | |
| 123 | warnings::enabled() now reports the state of $^W correctly if the caller |
| 124 | isn't using lexical warnings. |
| 125 | |
| 126 | =item Spurious warnings and errors |
| 127 | |
| 128 | Perl 5.6.0 could emit spurious warnings about redefinition of dl_error() |
| 129 | when statically building extensions into perl. This has been corrected. |
| 130 | |
| 131 | "our" variables could result in bogus "Variable will not stay shared" |
| 132 | warnings. This is now fixed. |
| 133 | |
| 134 | "our" variables of the same name declared in two sibling blocks |
| 135 | resulted in bogus warnings about "redeclaration" of the variables. |
| 136 | The problem has been corrected. |
| 137 | |
| 138 | =item glob() |
| 139 | |
| 140 | Compatibility of the builtin glob() with old csh-based glob has been |
| 141 | improved with the addition of GLOB_ALPHASORT option. See C<File::Glob>. |
| 142 | |
| 143 | File::Glob::glob() has been renamed to File::Glob::bsd_glob() |
| 144 | because the name clashes with the builtin glob(). The older |
| 145 | name is still available for compatibility, but is deprecated. |
| 146 | |
| 147 | Spurious syntax errors generated in certain situations, when glob() |
| 148 | caused File::Glob to be loaded for the first time, have been fixed. |
| 149 | |
| 150 | =item Tainting |
| 151 | |
| 152 | Some cases of inconsistent taint propagation (such as within hash |
| 153 | values) have been fixed. |
| 154 | |
| 155 | The tainting behavior of sprintf() has been rationalized. It does |
| 156 | not taint the result of floating point formats anymore, making the |
| 157 | behavior consistent with that of string interpolation. |
| 158 | |
| 159 | =item sort() |
| 160 | |
| 161 | Arguments to sort() weren't being provided the right wantarray() context. |
| 162 | The comparison block is now run in scalar context, and the arguments to |
| 163 | be sorted are always provided list context. |
| 164 | |
| 165 | sort() is also fully reentrant, in the sense that the sort function |
| 166 | can itself call sort(). This did not work reliably in previous releases. |
| 167 | |
| 168 | =item #line directives |
| 169 | |
| 170 | #line directives now work correctly when they appear at the very |
| 171 | beginning of C<eval "...">. |
| 172 | |
| 173 | =item Subroutine prototypes |
| 174 | |
| 175 | The (\&) prototype now works properly. |
| 176 | |
| 177 | =item map() |
| 178 | |
| 179 | map() could get pathologically slow when the result list it generates |
| 180 | is larger than the source list. The performance has been improved for |
| 181 | common scenarios. |
| 182 | |
| 183 | =item Debugger |
| 184 | |
| 185 | Debugger exit code now reflects the script exit code. |
| 186 | |
| 187 | Condition C<"0"> in breakpoints is now treated correctly. |
| 188 | |
| 189 | The C<d> command now checks the line number. |
| 190 | |
| 191 | C<$.> is no longer corrupted by the debugger. |
| 192 | |
| 193 | All debugger output now correctly goes to the socket if RemotePort |
| 194 | is set. |
| 195 | |
| 196 | =item PERL5OPT |
| 197 | |
| 198 | PERL5OPT can be set to more than one switch group. Previously, |
| 199 | it used to be limited to one group of options only. |
| 200 | |
| 201 | =item chop() |
| 202 | |
| 203 | chop(@list) in list context returned the characters chopped in reverse |
| 204 | order. This has been reversed to be in the right order. |
| 205 | |
| 206 | =item Unicode support |
| 207 | |
| 208 | Unicode support has seen a large number of incremental improvements, |
| 209 | but continues to be highly experimental. It is not expected to be |
| 210 | fully supported in the 5.6.x maintenance releases. |
| 211 | |
| 212 | substr(), join(), repeat(), reverse(), quotemeta() and string |
| 213 | concatenation were all handling Unicode strings incorrectly in |
| 214 | Perl 5.6.0. This has been corrected. |
| 215 | |
| 216 | Support for C<tr///CU> and C<tr///UC> etc., have been removed since |
| 217 | we realized the interface is broken. For similar functionality, |
| 218 | see L<perlfunc/pack>. |
| 219 | |
| 220 | The Unicode Character Database has been updated to version 3.0.1 |
| 221 | with additions made available to the public as of August 30, 2000. |
| 222 | |
| 223 | The Unicode character classes \p{Blank} and \p{SpacePerl} have been |
| 224 | added. "Blank" is like C isblank(), that is, it contains only |
| 225 | "horizontal whitespace" (the space character is, the newline isn't), |
| 226 | and the "SpacePerl" is the Unicode equivalent of C<\s> (\p{Space} |
| 227 | isn't, since that includes the vertical tabulator character, whereas |
| 228 | C<\s> doesn't.) |
| 229 | |
| 230 | If you are experimenting with Unicode support in perl, the development |
| 231 | versions of Perl may have more to offer. In particular, I/O layers |
| 232 | are now available in the development track, but not in the maintenance |
| 233 | track, primarily to do backward compatibility issues. Unicode support |
| 234 | is also evolving rapidly on a daily basis in the development track--the |
| 235 | maintenance track only reflects the most conservative of these changes. |
| 236 | |
| 237 | =item 64-bit support |
| 238 | |
| 239 | Support for 64-bit platforms has been improved, but continues to be |
| 240 | experimental. The level of support varies greatly among platforms. |
| 241 | |
| 242 | =item Compiler |
| 243 | |
| 244 | The B Compiler and its various backends have had many incremental |
| 245 | improvements, but they continue to remain highly experimental. Use in |
| 246 | production environments is discouraged. |
| 247 | |
| 248 | The perlcc tool has been rewritten so that the user interface is much |
| 249 | more like that of a C compiler. |
| 250 | |
| 251 | The perlbc tools has been removed. Use C<perlcc -B> instead. |
| 252 | |
| 253 | =item Lvalue subroutines |
| 254 | |
| 255 | There have been various bugfixes to support lvalue subroutines better. |
| 256 | However, the feature still remains experimental. |
| 257 | |
| 258 | =item IO::Socket |
| 259 | |
| 260 | IO::Socket::INET failed to open the specified port if the service |
| 261 | name was not known. It now correctly uses the supplied port number |
| 262 | as is. |
| 263 | |
| 264 | =item File::Find |
| 265 | |
| 266 | File::Find now chdir()s correctly when chasing symbolic links. |
| 267 | |
| 268 | =item xsubpp |
| 269 | |
| 270 | xsubpp now tolerates embedded POD sections. |
| 271 | |
| 272 | =item C<no Module;> |
| 273 | |
| 274 | C<no Module;> does not produce an error even if Module does not have an |
| 275 | unimport() method. This parallels the behavior of C<use> vis-a-vis |
| 276 | C<import>. |
| 277 | |
| 278 | =item Tests |
| 279 | |
| 280 | A large number of tests have been added. |
| 281 | |
| 282 | =back |
| 283 | |
| 284 | =head2 Core features |
| 285 | |
| 286 | untie() will now call an UNTIE() hook if it exists. See L<perltie> |
| 287 | for details. |
| 288 | |
| 289 | The C<-DT> command line switch outputs copious tokenizing information. |
| 290 | See L<perlrun>. |
| 291 | |
| 292 | Arrays are now always interpolated in double-quotish strings. Previously, |
| 293 | C<"foo@bar.com"> used to be a fatal error at compile time, if an array |
| 294 | C<@bar> was not used or declared. This transitional behavior was |
| 295 | intended to help migrate perl4 code, and is deemed to be no longer useful. |
| 296 | See L</"Arrays now always interpolate into double-quoted strings">. |
| 297 | |
| 298 | keys(), each(), pop(), push(), shift(), splice() and unshift() |
| 299 | can all be overridden now. |
| 300 | |
| 301 | C<my __PACKAGE__ $obj> now does the expected thing. |
| 302 | |
| 303 | =head2 Configuration issues |
| 304 | |
| 305 | On some systems (IRIX and Solaris among them) the system malloc is demonstrably |
| 306 | better. While the defaults haven't been changed in order to retain binary |
| 307 | compatibility with earlier releases, you may be better off building perl |
| 308 | with C<Configure -Uusemymalloc ...> as discussed in the F<INSTALL> file. |
| 309 | |
| 310 | C<Configure> has been enhanced in various ways: |
| 311 | |
| 312 | =over |
| 313 | |
| 314 | =item * |
| 315 | |
| 316 | Minimizes use of temporary files. |
| 317 | |
| 318 | =item * |
| 319 | |
| 320 | By default, does not link perl with libraries not used by it, such as |
| 321 | the various dbm libraries. SunOS 4.x hints preserve behavior on that |
| 322 | platform. |
| 323 | |
| 324 | =item * |
| 325 | |
| 326 | Support for pdp11-style memory models has been removed due to obsolescence. |
| 327 | |
| 328 | =item * |
| 329 | |
| 330 | Building outside the source tree is supported on systems that have |
| 331 | symbolic links. This is done by running |
| 332 | |
| 333 | sh /path/to/source/Configure -Dmksymlinks ... |
| 334 | make all test install |
| 335 | |
| 336 | in a directory other than the perl source directory. See F<INSTALL>. |
| 337 | |
| 338 | =item * |
| 339 | |
| 340 | C<Configure -S> can be run non-interactively. |
| 341 | |
| 342 | =back |
| 343 | |
| 344 | =head2 Documentation |
| 345 | |
| 346 | README.aix, README.solaris and README.macos have been added. |
| 347 | README.posix-bc has been renamed to README.bs2000. These are |
| 348 | installed as L<perlaix>, L<perlsolaris>, L<perlmacos>, and |
| 349 | L<perlbs2000> respectively. |
| 350 | |
| 351 | The following pod documents are brand new: |
| 352 | |
| 353 | perlclib Internal replacements for standard C library functions |
| 354 | perldebtut Perl debugging tutorial |
| 355 | perlebcdic Considerations for running Perl on EBCDIC platforms |
| 356 | perlnewmod Perl modules: preparing a new module for distribution |
| 357 | perlrequick Perl regular expressions quick start |
| 358 | perlretut Perl regular expressions tutorial |
| 359 | perlutil utilities packaged with the Perl distribution |
| 360 | |
| 361 | The F<INSTALL> file has been expanded to cover various issues, such as |
| 362 | 64-bit support. |
| 363 | |
| 364 | A longer list of contributors has been added to the source distribution. |
| 365 | See the file C<AUTHORS>. |
| 366 | |
| 367 | Numerous other changes have been made to the included documentation and FAQs. |
| 368 | |
| 369 | =head2 Bundled modules |
| 370 | |
| 371 | The following modules have been added. |
| 372 | |
| 373 | =over |
| 374 | |
| 375 | =item B::Concise |
| 376 | |
| 377 | Walks Perl syntax tree, printing concise info about ops. See L<B::Concise>. |
| 378 | |
| 379 | =item File::Temp |
| 380 | |
| 381 | Returns name and handle of a temporary file safely. See L<File::Temp>. |
| 382 | |
| 383 | =item Pod::LaTeX |
| 384 | |
| 385 | Converts Pod data to formatted LaTeX. See L<Pod::LaTeX>. |
| 386 | |
| 387 | =item Pod::Text::Overstrike |
| 388 | |
| 389 | Converts POD data to formatted overstrike text. See L<Pod::Text::Overstrike>. |
| 390 | |
| 391 | =back |
| 392 | |
| 393 | The following modules have been upgraded. |
| 394 | |
| 395 | =over |
| 396 | |
| 397 | =item CGI |
| 398 | |
| 399 | CGI v2.752 is now included. |
| 400 | |
| 401 | =item CPAN |
| 402 | |
| 403 | CPAN v1.59_54 is now included. |
| 404 | |
| 405 | =item Class::Struct |
| 406 | |
| 407 | Various bugfixes have been added. |
| 408 | |
| 409 | =item DB_File |
| 410 | |
| 411 | DB_File v1.75 supports newer Berkeley DB versions, among other |
| 412 | improvements. |
| 413 | |
| 414 | =item Devel::Peek |
| 415 | |
| 416 | Devel::Peek has been enhanced to support dumping of memory statistics, |
| 417 | when perl is built with the included malloc(). |
| 418 | |
| 419 | =item File::Find |
| 420 | |
| 421 | File::Find now supports pre and post-processing of the files in order |
| 422 | to sort() them, etc. |
| 423 | |
| 424 | =item Getopt::Long |
| 425 | |
| 426 | Getopt::Long v2.25 is included. |
| 427 | |
| 428 | =item IO::Poll |
| 429 | |
| 430 | Various bug fixes have been included. |
| 431 | |
| 432 | =item IPC::Open3 |
| 433 | |
| 434 | IPC::Open3 allows use of numeric file descriptors. |
| 435 | |
| 436 | =item Math::BigFloat |
| 437 | |
| 438 | The fmod() function supports modulus operations. Various bug fixes |
| 439 | have also been included. |
| 440 | |
| 441 | =item Math::Complex |
| 442 | |
| 443 | Math::Complex handles inf, NaN etc., better. |
| 444 | |
| 445 | =item Net::Ping |
| 446 | |
| 447 | ping() could fail on odd number of data bytes, and when the echo service |
| 448 | isn't running. This has been corrected. |
| 449 | |
| 450 | =item Opcode |
| 451 | |
| 452 | A memory leak has been fixed. |
| 453 | |
| 454 | =item Pod::Parser |
| 455 | |
| 456 | Version 1.13 of the Pod::Parser suite is included. |
| 457 | |
| 458 | =item Pod::Text |
| 459 | |
| 460 | Pod::Text and related modules have been upgraded to the versions |
| 461 | in podlators suite v2.08. |
| 462 | |
| 463 | =item SDBM_File |
| 464 | |
| 465 | On dosish platforms, some keys went missing because of lack of support for |
| 466 | files with "holes". A workaround for the problem has been added. |
| 467 | |
| 468 | =item Sys::Syslog |
| 469 | |
| 470 | Various bug fixes have been included. |
| 471 | |
| 472 | =item Tie::RefHash |
| 473 | |
| 474 | Now supports Tie::RefHash::Nestable to automagically tie hashref values. |
| 475 | |
| 476 | =item Tie::SubstrHash |
| 477 | |
| 478 | Various bug fixes have been included. |
| 479 | |
| 480 | =back |
| 481 | |
| 482 | =head2 Platform-specific improvements |
| 483 | |
| 484 | The following new ports are now available. |
| 485 | |
| 486 | =over |
| 487 | |
| 488 | =item NCR MP-RAS |
| 489 | |
| 490 | =item NonStop-UX |
| 491 | |
| 492 | =back |
| 493 | |
| 494 | Perl now builds under Amdahl UTS. |
| 495 | |
| 496 | Perl has also been verified to build under Amiga OS. |
| 497 | |
| 498 | Support for EPOC has been much improved. See README.epoc. |
| 499 | |
| 500 | Building perl with -Duseithreads or -Duse5005threads now works |
| 501 | under HP-UX 10.20 (previously it only worked under 10.30 or later). |
| 502 | You will need a thread library package installed. See README.hpux. |
| 503 | |
| 504 | Long doubles should now work under Linux. |
| 505 | |
| 506 | Mac OS Classic is now supported in the mainstream source package. |
| 507 | See README.macos. |
| 508 | |
| 509 | Support for MPE/iX has been updated. See README.mpeix. |
| 510 | |
| 511 | Support for OS/2 has been improved. See C<os2/Changes> and README.os2. |
| 512 | |
| 513 | Dynamic loading on z/OS (formerly OS/390) has been improved. See |
| 514 | README.os390. |
| 515 | |
| 516 | Support for VMS has seen many incremental improvements, including |
| 517 | better support for operators like backticks and system(), and better |
| 518 | %ENV handling. See C<README.vms> and L<perlvms>. |
| 519 | |
| 520 | Support for Stratus VOS has been improved. See C<vos/Changes> and README.vos. |
| 521 | |
| 522 | Support for Windows has been improved. |
| 523 | |
| 524 | =over |
| 525 | |
| 526 | =item * |
| 527 | |
| 528 | fork() emulation has been improved in various ways, but still continues |
| 529 | to be experimental. See L<perlfork> for known bugs and caveats. |
| 530 | |
| 531 | =item * |
| 532 | |
| 533 | %SIG has been enabled under USE_ITHREADS, but its use is completely |
| 534 | unsupported under all configurations. |
| 535 | |
| 536 | =item * |
| 537 | |
| 538 | Borland C++ v5.5 is now a supported compiler that can build Perl. |
| 539 | However, the generated binaries continue to be incompatible with those |
| 540 | generated by the other supported compilers (GCC and Visual C++). |
| 541 | |
| 542 | =item * |
| 543 | |
| 544 | Non-blocking waits for child processes (or pseudo-processes) are |
| 545 | supported via C<waitpid($pid, &POSIX::WNOHANG)>. |
| 546 | |
| 547 | =item * |
| 548 | |
| 549 | A memory leak in accept() has been fixed. |
| 550 | |
| 551 | =item * |
| 552 | |
| 553 | wait(), waitpid() and backticks now return the correct exit status under |
| 554 | Windows 9x. |
| 555 | |
| 556 | =item * |
| 557 | |
| 558 | Trailing new %ENV entries weren't propagated to child processes. This |
| 559 | is now fixed. |
| 560 | |
| 561 | =item * |
| 562 | |
| 563 | Current directory entries in %ENV are now correctly propagated to child |
| 564 | processes. |
| 565 | |
| 566 | =item * |
| 567 | |
| 568 | Duping socket handles with open(F, ">&MYSOCK") now works under Windows 9x. |
| 569 | |
| 570 | =item * |
| 571 | |
| 572 | The makefiles now provide a single switch to bulk-enable all the features |
| 573 | enabled in ActiveState ActivePerl (a popular binary distribution). |
| 574 | |
| 575 | =item * |
| 576 | |
| 577 | Win32::GetCwd() correctly returns C:\ instead of C: when at the drive root. |
| 578 | Other bugs in chdir() and Cwd::cwd() have also been fixed. |
| 579 | |
| 580 | =item * |
| 581 | |
| 582 | fork() correctly returns undef and sets EAGAIN when it runs out of |
| 583 | pseudo-process handles. |
| 584 | |
| 585 | =item * |
| 586 | |
| 587 | ExtUtils::MakeMaker now uses $ENV{LIB} to search for libraries. |
| 588 | |
| 589 | =item * |
| 590 | |
| 591 | UNC path handling is better when perl is built to support fork(). |
| 592 | |
| 593 | =item * |
| 594 | |
| 595 | A handle leak in socket handling has been fixed. |
| 596 | |
| 597 | =item * |
| 598 | |
| 599 | send() works from within a pseudo-process. |
| 600 | |
| 601 | =back |
| 602 | |
| 603 | Unless specifically qualified otherwise, the remainder of this document |
| 604 | covers changes between the 5.005 and 5.6.0 releases. |
| 605 | |
| 606 | =head1 Core Enhancements |
| 607 | |
| 608 | =head2 Interpreter cloning, threads, and concurrency |
| 609 | |
| 610 | Perl 5.6.0 introduces the beginnings of support for running multiple |
| 611 | interpreters concurrently in different threads. In conjunction with |
| 612 | the perl_clone() API call, which can be used to selectively duplicate |
| 613 | the state of any given interpreter, it is possible to compile a |
| 614 | piece of code once in an interpreter, clone that interpreter |
| 615 | one or more times, and run all the resulting interpreters in distinct |
| 616 | threads. |
| 617 | |
| 618 | On the Windows platform, this feature is used to emulate fork() at the |
| 619 | interpreter level. See L<perlfork> for details about that. |
| 620 | |
| 621 | This feature is still in evolution. It is eventually meant to be used |
| 622 | to selectively clone a subroutine and data reachable from that |
| 623 | subroutine in a separate interpreter and run the cloned subroutine |
| 624 | in a separate thread. Since there is no shared data between the |
| 625 | interpreters, little or no locking will be needed (unless parts of |
| 626 | the symbol table are explicitly shared). This is obviously intended |
| 627 | to be an easy-to-use replacement for the existing threads support. |
| 628 | |
| 629 | Support for cloning interpreters and interpreter concurrency can be |
| 630 | enabled using the -Dusethreads Configure option (see win32/Makefile for |
| 631 | how to enable it on Windows.) The resulting perl executable will be |
| 632 | functionally identical to one that was built with -Dmultiplicity, but |
| 633 | the perl_clone() API call will only be available in the former. |
| 634 | |
| 635 | -Dusethreads enables the cpp macro USE_ITHREADS by default, which in turn |
| 636 | enables Perl source code changes that provide a clear separation between |
| 637 | the op tree and the data it operates with. The former is immutable, and |
| 638 | can therefore be shared between an interpreter and all of its clones, |
| 639 | while the latter is considered local to each interpreter, and is therefore |
| 640 | copied for each clone. |
| 641 | |
| 642 | Note that building Perl with the -Dusemultiplicity Configure option |
| 643 | is adequate if you wish to run multiple B<independent> interpreters |
| 644 | concurrently in different threads. -Dusethreads only provides the |
| 645 | additional functionality of the perl_clone() API call and other |
| 646 | support for running B<cloned> interpreters concurrently. |
| 647 | |
| 648 | NOTE: This is an experimental feature. Implementation details are |
| 649 | subject to change. |
| 650 | |
| 651 | =head2 Lexically scoped warning categories |
| 652 | |
| 653 | You can now control the granularity of warnings emitted by perl at a finer |
| 654 | level using the C<use warnings> pragma. L<warnings> and L<perllexwarn> |
| 655 | have copious documentation on this feature. |
| 656 | |
| 657 | =head2 Unicode and UTF-8 support |
| 658 | |
| 659 | Perl now uses UTF-8 as its internal representation for character |
| 660 | strings. The C<utf8> and C<bytes> pragmas are used to control this support |
| 661 | in the current lexical scope. See L<perlunicode>, L<utf8> and L<bytes> for |
| 662 | more information. |
| 663 | |
| 664 | This feature is expected to evolve quickly to support some form of I/O |
| 665 | disciplines that can be used to specify the kind of input and output data |
| 666 | (bytes or characters). Until that happens, additional modules from CPAN |
| 667 | will be needed to complete the toolkit for dealing with Unicode. |
| 668 | |
| 669 | NOTE: This should be considered an experimental feature. Implementation |
| 670 | details are subject to change. |
| 671 | |
| 672 | =head2 Support for interpolating named characters |
| 673 | |
| 674 | The new C<\N> escape interpolates named characters within strings. |
| 675 | For example, C<"Hi! \N{WHITE SMILING FACE}"> evaluates to a string |
| 676 | with a Unicode smiley face at the end. |
| 677 | |
| 678 | =head2 "our" declarations |
| 679 | |
| 680 | An "our" declaration introduces a value that can be best understood |
| 681 | as a lexically scoped symbolic alias to a global variable in the |
| 682 | package that was current where the variable was declared. This is |
| 683 | mostly useful as an alternative to the C<vars> pragma, but also provides |
| 684 | the opportunity to introduce typing and other attributes for such |
| 685 | variables. See L<perlfunc/our>. |
| 686 | |
| 687 | =head2 Support for strings represented as a vector of ordinals |
| 688 | |
| 689 | Literals of the form C<v1.2.3.4> are now parsed as a string composed |
| 690 | of characters with the specified ordinals. This is an alternative, more |
| 691 | readable way to construct (possibly Unicode) strings instead of |
| 692 | interpolating characters, as in C<"\x{1}\x{2}\x{3}\x{4}">. The leading |
| 693 | C<v> may be omitted if there are more than two ordinals, so C<1.2.3> is |
| 694 | parsed the same as C<v1.2.3>. |
| 695 | |
| 696 | Strings written in this form are also useful to represent version "numbers". |
| 697 | It is easy to compare such version "numbers" (which are really just plain |
| 698 | strings) using any of the usual string comparison operators C<eq>, C<ne>, |
| 699 | C<lt>, C<gt>, etc., or perform bitwise string operations on them using C<|>, |
| 700 | C<&>, etc. |
| 701 | |
| 702 | In conjunction with the new C<$^V> magic variable (which contains |
| 703 | the perl version as a string), such literals can be used as a readable way |
| 704 | to check if you're running a particular version of Perl: |
| 705 | |
| 706 | # this will parse in older versions of Perl also |
| 707 | if ($^V and $^V gt v5.6.0) { |
| 708 | # new features supported |
| 709 | } |
| 710 | |
| 711 | C<require> and C<use> also have some special magic to support such literals. |
| 712 | They will be interpreted as a version rather than as a module name: |
| 713 | |
| 714 | require v5.6.0; # croak if $^V lt v5.6.0 |
| 715 | use v5.6.0; # same, but croaks at compile-time |
| 716 | |
| 717 | Alternatively, the C<v> may be omitted if there is more than one dot: |
| 718 | |
| 719 | require 5.6.0; |
| 720 | use 5.6.0; |
| 721 | |
| 722 | Also, C<sprintf> and C<printf> support the Perl-specific format flag C<%v> |
| 723 | to print ordinals of characters in arbitrary strings: |
| 724 | |
| 725 | printf "v%vd", $^V; # prints current version, such as "v5.5.650" |
| 726 | printf "%*vX", ":", $addr; # formats IPv6 address |
| 727 | printf "%*vb", " ", $bits; # displays bitstring |
| 728 | |
| 729 | See L<perldata/"Scalar value constructors"> for additional information. |
| 730 | |
| 731 | =head2 Improved Perl version numbering system |
| 732 | |
| 733 | Beginning with Perl version 5.6.0, the version number convention has been |
| 734 | changed to a "dotted integer" scheme that is more commonly found in open |
| 735 | source projects. |
| 736 | |
| 737 | Maintenance versions of v5.6.0 will be released as v5.6.1, v5.6.2 etc. |
| 738 | The next development series following v5.6.0 will be numbered v5.7.x, |
| 739 | beginning with v5.7.0, and the next major production release following |
| 740 | v5.6.0 will be v5.8.0. |
| 741 | |
| 742 | The English module now sets $PERL_VERSION to $^V (a string value) rather |
| 743 | than C<$]> (a numeric value). (This is a potential incompatibility. |
| 744 | Send us a report via perlbug if you are affected by this.) |
| 745 | |
| 746 | The v1.2.3 syntax is also now legal in Perl. |
| 747 | See L<Support for strings represented as a vector of ordinals> for more on that. |
| 748 | |
| 749 | To cope with the new versioning system's use of at least three significant |
| 750 | digits for each version component, the method used for incrementing the |
| 751 | subversion number has also changed slightly. We assume that versions older |
| 752 | than v5.6.0 have been incrementing the subversion component in multiples of |
| 753 | 10. Versions after v5.6.0 will increment them by 1. Thus, using the new |
| 754 | notation, 5.005_03 is the "same" as v5.5.30, and the first maintenance |
| 755 | version following v5.6.0 will be v5.6.1 (which should be read as being |
| 756 | equivalent to a floating point value of 5.006_001 in the older format, |
| 757 | stored in C<$]>). |
| 758 | |
| 759 | =head2 New syntax for declaring subroutine attributes |
| 760 | |
| 761 | Formerly, if you wanted to mark a subroutine as being a method call or |
| 762 | as requiring an automatic lock() when it is entered, you had to declare |
| 763 | that with a C<use attrs> pragma in the body of the subroutine. |
| 764 | That can now be accomplished with declaration syntax, like this: |
| 765 | |
| 766 | sub mymethod : locked method; |
| 767 | ... |
| 768 | sub mymethod : locked method { |
| 769 | ... |
| 770 | } |
| 771 | |
| 772 | sub othermethod :locked :method; |
| 773 | ... |
| 774 | sub othermethod :locked :method { |
| 775 | ... |
| 776 | } |
| 777 | |
| 778 | |
| 779 | (Note how only the first C<:> is mandatory, and whitespace surrounding |
| 780 | the C<:> is optional.) |
| 781 | |
| 782 | F<AutoSplit.pm> and F<SelfLoader.pm> have been updated to keep the attributes |
| 783 | with the stubs they provide. See L<attributes>. |
| 784 | |
| 785 | =head2 File and directory handles can be autovivified |
| 786 | |
| 787 | Similar to how constructs such as C<< $x->[0] >> autovivify a reference, |
| 788 | handle constructors (open(), opendir(), pipe(), socketpair(), sysopen(), |
| 789 | socket(), and accept()) now autovivify a file or directory handle |
| 790 | if the handle passed to them is an uninitialized scalar variable. This |
| 791 | allows the constructs such as C<open(my $fh, ...)> and C<open(local $fh,...)> |
| 792 | to be used to create filehandles that will conveniently be closed |
| 793 | automatically when the scope ends, provided there are no other references |
| 794 | to them. This largely eliminates the need for typeglobs when opening |
| 795 | filehandles that must be passed around, as in the following example: |
| 796 | |
| 797 | sub myopen { |
| 798 | open my $fh, "@_" |
| 799 | or die "Can't open '@_': $!"; |
| 800 | return $fh; |
| 801 | } |
| 802 | |
| 803 | { |
| 804 | my $f = myopen("</etc/motd"); |
| 805 | print <$f>; |
| 806 | # $f implicitly closed here |
| 807 | } |
| 808 | |
| 809 | =head2 open() with more than two arguments |
| 810 | |
| 811 | If open() is passed three arguments instead of two, the second argument |
| 812 | is used as the mode and the third argument is taken to be the file name. |
| 813 | This is primarily useful for protecting against unintended magic behavior |
| 814 | of the traditional two-argument form. See L<perlfunc/open>. |
| 815 | |
| 816 | =head2 64-bit support |
| 817 | |
| 818 | Any platform that has 64-bit integers either |
| 819 | |
| 820 | (1) natively as longs or ints |
| 821 | (2) via special compiler flags |
| 822 | (3) using long long or int64_t |
| 823 | |
| 824 | is able to use "quads" (64-bit integers) as follows: |
| 825 | |
| 826 | =over 4 |
| 827 | |
| 828 | =item * |
| 829 | |
| 830 | constants (decimal, hexadecimal, octal, binary) in the code |
| 831 | |
| 832 | =item * |
| 833 | |
| 834 | arguments to oct() and hex() |
| 835 | |
| 836 | =item * |
| 837 | |
| 838 | arguments to print(), printf() and sprintf() (flag prefixes ll, L, q) |
| 839 | |
| 840 | =item * |
| 841 | |
| 842 | printed as such |
| 843 | |
| 844 | =item * |
| 845 | |
| 846 | pack() and unpack() "q" and "Q" formats |
| 847 | |
| 848 | =item * |
| 849 | |
| 850 | in basic arithmetics: + - * / % (NOTE: operating close to the limits |
| 851 | of the integer values may produce surprising results) |
| 852 | |
| 853 | =item * |
| 854 | |
| 855 | in bit arithmetics: & | ^ ~ << >> (NOTE: these used to be forced |
| 856 | to be 32 bits wide but now operate on the full native width.) |
| 857 | |
| 858 | =item * |
| 859 | |
| 860 | vec() |
| 861 | |
| 862 | =back |
| 863 | |
| 864 | Note that unless you have the case (a) you will have to configure |
| 865 | and compile Perl using the -Duse64bitint Configure flag. |
| 866 | |
| 867 | NOTE: The Configure flags -Duselonglong and -Duse64bits have been |
| 868 | deprecated. Use -Duse64bitint instead. |
| 869 | |
| 870 | There are actually two modes of 64-bitness: the first one is achieved |
| 871 | using Configure -Duse64bitint and the second one using Configure |
| 872 | -Duse64bitall. The difference is that the first one is minimal and |
| 873 | the second one maximal. The first works in more places than the second. |
| 874 | |
| 875 | The C<use64bitint> does only as much as is required to get 64-bit |
| 876 | integers into Perl (this may mean, for example, using "long longs") |
| 877 | while your memory may still be limited to 2 gigabytes (because your |
| 878 | pointers could still be 32-bit). Note that the name C<64bitint> does |
| 879 | not imply that your C compiler will be using 64-bit C<int>s (it might, |
| 880 | but it doesn't have to): the C<use64bitint> means that you will be |
| 881 | able to have 64 bits wide scalar values. |
| 882 | |
| 883 | The C<use64bitall> goes all the way by attempting to switch also |
| 884 | integers (if it can), longs (and pointers) to being 64-bit. This may |
| 885 | create an even more binary incompatible Perl than -Duse64bitint: the |
| 886 | resulting executable may not run at all in a 32-bit box, or you may |
| 887 | have to reboot/reconfigure/rebuild your operating system to be 64-bit |
| 888 | aware. |
| 889 | |
| 890 | Natively 64-bit systems like Alpha and Cray need neither -Duse64bitint |
| 891 | nor -Duse64bitall. |
| 892 | |
| 893 | Last but not least: note that due to Perl's habit of always using |
| 894 | floating point numbers, the quads are still not true integers. |
| 895 | When quads overflow their limits (0...18_446_744_073_709_551_615 unsigned, |
| 896 | -9_223_372_036_854_775_808...9_223_372_036_854_775_807 signed), they |
| 897 | are silently promoted to floating point numbers, after which they will |
| 898 | start losing precision (in their lower digits). |
| 899 | |
| 900 | NOTE: 64-bit support is still experimental on most platforms. |
| 901 | Existing support only covers the LP64 data model. In particular, the |
| 902 | LLP64 data model is not yet supported. 64-bit libraries and system |
| 903 | APIs on many platforms have not stabilized--your mileage may vary. |
| 904 | |
| 905 | =head2 Large file support |
| 906 | |
| 907 | If you have filesystems that support "large files" (files larger than |
| 908 | 2 gigabytes), you may now also be able to create and access them from |
| 909 | Perl. |
| 910 | |
| 911 | NOTE: The default action is to enable large file support, if |
| 912 | available on the platform. |
| 913 | |
| 914 | If the large file support is on, and you have a Fcntl constant |
| 915 | O_LARGEFILE, the O_LARGEFILE is automatically added to the flags |
| 916 | of sysopen(). |
| 917 | |
| 918 | Beware that unless your filesystem also supports "sparse files" seeking |
| 919 | to umpteen petabytes may be inadvisable. |
| 920 | |
| 921 | Note that in addition to requiring a proper file system to do large |
| 922 | files you may also need to adjust your per-process (or your |
| 923 | per-system, or per-process-group, or per-user-group) maximum filesize |
| 924 | limits before running Perl scripts that try to handle large files, |
| 925 | especially if you intend to write such files. |
| 926 | |
| 927 | Finally, in addition to your process/process group maximum filesize |
| 928 | limits, you may have quota limits on your filesystems that stop you |
| 929 | (your user id or your user group id) from using large files. |
| 930 | |
| 931 | Adjusting your process/user/group/file system/operating system limits |
| 932 | is outside the scope of Perl core language. For process limits, you |
| 933 | may try increasing the limits using your shell's limits/limit/ulimit |
| 934 | command before running Perl. The BSD::Resource extension (not |
| 935 | included with the standard Perl distribution) may also be of use, it |
| 936 | offers the getrlimit/setrlimit interface that can be used to adjust |
| 937 | process resource usage limits, including the maximum filesize limit. |
| 938 | |
| 939 | =head2 Long doubles |
| 940 | |
| 941 | In some systems you may be able to use long doubles to enhance the |
| 942 | range and precision of your double precision floating point numbers |
| 943 | (that is, Perl's numbers). Use Configure -Duselongdouble to enable |
| 944 | this support (if it is available). |
| 945 | |
| 946 | =head2 "more bits" |
| 947 | |
| 948 | You can "Configure -Dusemorebits" to turn on both the 64-bit support |
| 949 | and the long double support. |
| 950 | |
| 951 | =head2 Enhanced support for sort() subroutines |
| 952 | |
| 953 | Perl subroutines with a prototype of C<($$)>, and XSUBs in general, can |
| 954 | now be used as sort subroutines. In either case, the two elements to |
| 955 | be compared are passed as normal parameters in @_. See L<perlfunc/sort>. |
| 956 | |
| 957 | For unprototyped sort subroutines, the historical behavior of passing |
| 958 | the elements to be compared as the global variables $a and $b remains |
| 959 | unchanged. |
| 960 | |
| 961 | =head2 C<sort $coderef @foo> allowed |
| 962 | |
| 963 | sort() did not accept a subroutine reference as the comparison |
| 964 | function in earlier versions. This is now permitted. |
| 965 | |
| 966 | =head2 File globbing implemented internally |
| 967 | |
| 968 | Perl now uses the File::Glob implementation of the glob() operator |
| 969 | automatically. This avoids using an external csh process and the |
| 970 | problems associated with it. |
| 971 | |
| 972 | NOTE: This is currently an experimental feature. Interfaces and |
| 973 | implementation are subject to change. |
| 974 | |
| 975 | =head2 Support for CHECK blocks |
| 976 | |
| 977 | In addition to C<BEGIN>, C<INIT>, C<END>, C<DESTROY> and C<AUTOLOAD>, |
| 978 | subroutines named C<CHECK> are now special. These are queued up during |
| 979 | compilation and behave similar to END blocks, except they are called at |
| 980 | the end of compilation rather than at the end of execution. They cannot |
| 981 | be called directly. |
| 982 | |
| 983 | =head2 POSIX character class syntax [: :] supported |
| 984 | |
| 985 | For example to match alphabetic characters use /[[:alpha:]]/. |
| 986 | See L<perlre> for details. |
| 987 | |
| 988 | =head2 Better pseudo-random number generator |
| 989 | |
| 990 | In 5.005_0x and earlier, perl's rand() function used the C library |
| 991 | rand(3) function. As of 5.005_52, Configure tests for drand48(), |
| 992 | random(), and rand() (in that order) and picks the first one it finds. |
| 993 | |
| 994 | These changes should result in better random numbers from rand(). |
| 995 | |
| 996 | =head2 Improved C<qw//> operator |
| 997 | |
| 998 | The C<qw//> operator is now evaluated at compile time into a true list |
| 999 | instead of being replaced with a run time call to C<split()>. This |
| 1000 | removes the confusing misbehaviour of C<qw//> in scalar context, which |
| 1001 | had inherited that behaviour from split(). |
| 1002 | |
| 1003 | Thus: |
| 1004 | |
| 1005 | $foo = ($bar) = qw(a b c); print "$foo|$bar\n"; |
| 1006 | |
| 1007 | now correctly prints "3|a", instead of "2|a". |
| 1008 | |
| 1009 | =head2 Better worst-case behavior of hashes |
| 1010 | |
| 1011 | Small changes in the hashing algorithm have been implemented in |
| 1012 | order to improve the distribution of lower order bits in the |
| 1013 | hashed value. This is expected to yield better performance on |
| 1014 | keys that are repeated sequences. |
| 1015 | |
| 1016 | =head2 pack() format 'Z' supported |
| 1017 | |
| 1018 | The new format type 'Z' is useful for packing and unpacking null-terminated |
| 1019 | strings. See L<perlfunc/"pack">. |
| 1020 | |
| 1021 | =head2 pack() format modifier '!' supported |
| 1022 | |
| 1023 | The new format type modifier '!' is useful for packing and unpacking |
| 1024 | native shorts, ints, and longs. See L<perlfunc/"pack">. |
| 1025 | |
| 1026 | =head2 pack() and unpack() support counted strings |
| 1027 | |
| 1028 | The template character '/' can be used to specify a counted string |
| 1029 | type to be packed or unpacked. See L<perlfunc/"pack">. |
| 1030 | |
| 1031 | =head2 Comments in pack() templates |
| 1032 | |
| 1033 | The '#' character in a template introduces a comment up to |
| 1034 | end of the line. This facilitates documentation of pack() |
| 1035 | templates. |
| 1036 | |
| 1037 | =head2 Weak references |
| 1038 | |
| 1039 | In previous versions of Perl, you couldn't cache objects so as |
| 1040 | to allow them to be deleted if the last reference from outside |
| 1041 | the cache is deleted. The reference in the cache would hold a |
| 1042 | reference count on the object and the objects would never be |
| 1043 | destroyed. |
| 1044 | |
| 1045 | Another familiar problem is with circular references. When an |
| 1046 | object references itself, its reference count would never go |
| 1047 | down to zero, and it would not get destroyed until the program |
| 1048 | is about to exit. |
| 1049 | |
| 1050 | Weak references solve this by allowing you to "weaken" any |
| 1051 | reference, that is, make it not count towards the reference count. |
| 1052 | When the last non-weak reference to an object is deleted, the object |
| 1053 | is destroyed and all the weak references to the object are |
| 1054 | automatically undef-ed. |
| 1055 | |
| 1056 | To use this feature, you need the Devel::WeakRef package from CPAN, which |
| 1057 | contains additional documentation. |
| 1058 | |
| 1059 | NOTE: This is an experimental feature. Details are subject to change. |
| 1060 | |
| 1061 | =head2 Binary numbers supported |
| 1062 | |
| 1063 | Binary numbers are now supported as literals, in s?printf formats, and |
| 1064 | C<oct()>: |
| 1065 | |
| 1066 | $answer = 0b101010; |
| 1067 | printf "The answer is: %b\n", oct("0b101010"); |
| 1068 | |
| 1069 | =head2 Lvalue subroutines |
| 1070 | |
| 1071 | Subroutines can now return modifiable lvalues. |
| 1072 | See L<perlsub/"Lvalue subroutines">. |
| 1073 | |
| 1074 | NOTE: This is an experimental feature. Details are subject to change. |
| 1075 | |
| 1076 | =head2 Some arrows may be omitted in calls through references |
| 1077 | |
| 1078 | Perl now allows the arrow to be omitted in many constructs |
| 1079 | involving subroutine calls through references. For example, |
| 1080 | C<< $foo[10]->('foo') >> may now be written C<$foo[10]('foo')>. |
| 1081 | This is rather similar to how the arrow may be omitted from |
| 1082 | C<< $foo[10]->{'foo'} >>. Note however, that the arrow is still |
| 1083 | required for C<< foo(10)->('bar') >>. |
| 1084 | |
| 1085 | =head2 Boolean assignment operators are legal lvalues |
| 1086 | |
| 1087 | Constructs such as C<($a ||= 2) += 1> are now allowed. |
| 1088 | |
| 1089 | =head2 exists() is supported on subroutine names |
| 1090 | |
| 1091 | The exists() builtin now works on subroutine names. A subroutine |
| 1092 | is considered to exist if it has been declared (even if implicitly). |
| 1093 | See L<perlfunc/exists> for examples. |
| 1094 | |
| 1095 | =head2 exists() and delete() are supported on array elements |
| 1096 | |
| 1097 | The exists() and delete() builtins now work on simple arrays as well. |
| 1098 | The behavior is similar to that on hash elements. |
| 1099 | |
| 1100 | exists() can be used to check whether an array element has been |
| 1101 | initialized. This avoids autovivifying array elements that don't exist. |
| 1102 | If the array is tied, the EXISTS() method in the corresponding tied |
| 1103 | package will be invoked. |
| 1104 | |
| 1105 | delete() may be used to remove an element from the array and return |
| 1106 | it. The array element at that position returns to its uninitialized |
| 1107 | state, so that testing for the same element with exists() will return |
| 1108 | false. If the element happens to be the one at the end, the size of |
| 1109 | the array also shrinks up to the highest element that tests true for |
| 1110 | exists(), or 0 if none such is found. If the array is tied, the DELETE() |
| 1111 | method in the corresponding tied package will be invoked. |
| 1112 | |
| 1113 | See L<perlfunc/exists> and L<perlfunc/delete> for examples. |
| 1114 | |
| 1115 | =head2 Pseudo-hashes work better |
| 1116 | |
| 1117 | Dereferencing some types of reference values in a pseudo-hash, |
| 1118 | such as C<< $ph->{foo}[1] >>, was accidentally disallowed. This has |
| 1119 | been corrected. |
| 1120 | |
| 1121 | When applied to a pseudo-hash element, exists() now reports whether |
| 1122 | the specified value exists, not merely if the key is valid. |
| 1123 | |
| 1124 | delete() now works on pseudo-hashes. When given a pseudo-hash element |
| 1125 | or slice it deletes the values corresponding to the keys (but not the keys |
| 1126 | themselves). See L<perlref/"Pseudo-hashes: Using an array as a hash">. |
| 1127 | |
| 1128 | Pseudo-hash slices with constant keys are now optimized to array lookups |
| 1129 | at compile-time. |
| 1130 | |
| 1131 | List assignments to pseudo-hash slices are now supported. |
| 1132 | |
| 1133 | The C<fields> pragma now provides ways to create pseudo-hashes, via |
| 1134 | fields::new() and fields::phash(). See L<fields>. |
| 1135 | |
| 1136 | NOTE: The pseudo-hash data type continues to be experimental. |
| 1137 | Limiting oneself to the interface elements provided by the |
| 1138 | fields pragma will provide protection from any future changes. |
| 1139 | |
| 1140 | =head2 Automatic flushing of output buffers |
| 1141 | |
| 1142 | fork(), exec(), system(), qx//, and pipe open()s now flush buffers |
| 1143 | of all files opened for output when the operation was attempted. This |
| 1144 | mostly eliminates confusing buffering mishaps suffered by users unaware |
| 1145 | of how Perl internally handles I/O. |
| 1146 | |
| 1147 | This is not supported on some platforms like Solaris where a suitably |
| 1148 | correct implementation of fflush(NULL) isn't available. |
| 1149 | |
| 1150 | =head2 Better diagnostics on meaningless filehandle operations |
| 1151 | |
| 1152 | Constructs such as C<< open(<FH>) >> and C<< close(<FH>) >> |
| 1153 | are compile time errors. Attempting to read from filehandles that |
| 1154 | were opened only for writing will now produce warnings (just as |
| 1155 | writing to read-only filehandles does). |
| 1156 | |
| 1157 | =head2 Where possible, buffered data discarded from duped input filehandle |
| 1158 | |
| 1159 | C<< open(NEW, "<&OLD") >> now attempts to discard any data that |
| 1160 | was previously read and buffered in C<OLD> before duping the handle. |
| 1161 | On platforms where doing this is allowed, the next read operation |
| 1162 | on C<NEW> will return the same data as the corresponding operation |
| 1163 | on C<OLD>. Formerly, it would have returned the data from the start |
| 1164 | of the following disk block instead. |
| 1165 | |
| 1166 | =head2 eof() has the same old magic as <> |
| 1167 | |
| 1168 | C<eof()> would return true if no attempt to read from C<< <> >> had |
| 1169 | yet been made. C<eof()> has been changed to have a little magic of its |
| 1170 | own, it now opens the C<< <> >> files. |
| 1171 | |
| 1172 | =head2 binmode() can be used to set :crlf and :raw modes |
| 1173 | |
| 1174 | binmode() now accepts a second argument that specifies a discipline |
| 1175 | for the handle in question. The two pseudo-disciplines ":raw" and |
| 1176 | ":crlf" are currently supported on DOS-derivative platforms. |
| 1177 | See L<perlfunc/"binmode"> and L<open>. |
| 1178 | |
| 1179 | =head2 C<-T> filetest recognizes UTF-8 encoded files as "text" |
| 1180 | |
| 1181 | The algorithm used for the C<-T> filetest has been enhanced to |
| 1182 | correctly identify UTF-8 content as "text". |
| 1183 | |
| 1184 | =head2 system(), backticks and pipe open now reflect exec() failure |
| 1185 | |
| 1186 | On Unix and similar platforms, system(), qx() and open(FOO, "cmd |") |
| 1187 | etc., are implemented via fork() and exec(). When the underlying |
| 1188 | exec() fails, earlier versions did not report the error properly, |
| 1189 | since the exec() happened to be in a different process. |
| 1190 | |
| 1191 | The child process now communicates with the parent about the |
| 1192 | error in launching the external command, which allows these |
| 1193 | constructs to return with their usual error value and set $!. |
| 1194 | |
| 1195 | =head2 Improved diagnostics |
| 1196 | |
| 1197 | Line numbers are no longer suppressed (under most likely circumstances) |
| 1198 | during the global destruction phase. |
| 1199 | |
| 1200 | Diagnostics emitted from code running in threads other than the main |
| 1201 | thread are now accompanied by the thread ID. |
| 1202 | |
| 1203 | Embedded null characters in diagnostics now actually show up. They |
| 1204 | used to truncate the message in prior versions. |
| 1205 | |
| 1206 | $foo::a and $foo::b are now exempt from "possible typo" warnings only |
| 1207 | if sort() is encountered in package C<foo>. |
| 1208 | |
| 1209 | Unrecognized alphabetic escapes encountered when parsing quote |
| 1210 | constructs now generate a warning, since they may take on new |
| 1211 | semantics in later versions of Perl. |
| 1212 | |
| 1213 | Many diagnostics now report the internal operation in which the warning |
| 1214 | was provoked, like so: |
| 1215 | |
| 1216 | Use of uninitialized value in concatenation (.) at (eval 1) line 1. |
| 1217 | Use of uninitialized value in print at (eval 1) line 1. |
| 1218 | |
| 1219 | Diagnostics that occur within eval may also report the file and line |
| 1220 | number where the eval is located, in addition to the eval sequence |
| 1221 | number and the line number within the evaluated text itself. For |
| 1222 | example: |
| 1223 | |
| 1224 | Not enough arguments for scalar at (eval 4)[newlib/perl5db.pl:1411] line 2, at EOF |
| 1225 | |
| 1226 | =head2 Diagnostics follow STDERR |
| 1227 | |
| 1228 | Diagnostic output now goes to whichever file the C<STDERR> handle |
| 1229 | is pointing at, instead of always going to the underlying C runtime |
| 1230 | library's C<stderr>. |
| 1231 | |
| 1232 | =head2 More consistent close-on-exec behavior |
| 1233 | |
| 1234 | On systems that support a close-on-exec flag on filehandles, the |
| 1235 | flag is now set for any handles created by pipe(), socketpair(), |
| 1236 | socket(), and accept(), if that is warranted by the value of $^F |
| 1237 | that may be in effect. Earlier versions neglected to set the flag |
| 1238 | for handles created with these operators. See L<perlfunc/pipe>, |
| 1239 | L<perlfunc/socketpair>, L<perlfunc/socket>, L<perlfunc/accept>, |
| 1240 | and L<perlvar/$^F>. |
| 1241 | |
| 1242 | =head2 syswrite() ease-of-use |
| 1243 | |
| 1244 | The length argument of C<syswrite()> has become optional. |
| 1245 | |
| 1246 | =head2 Better syntax checks on parenthesized unary operators |
| 1247 | |
| 1248 | Expressions such as: |
| 1249 | |
| 1250 | print defined(&foo,&bar,&baz); |
| 1251 | print uc("foo","bar","baz"); |
| 1252 | undef($foo,&bar); |
| 1253 | |
| 1254 | used to be accidentally allowed in earlier versions, and produced |
| 1255 | unpredictable behaviour. Some produced ancillary warnings |
| 1256 | when used in this way; others silently did the wrong thing. |
| 1257 | |
| 1258 | The parenthesized forms of most unary operators that expect a single |
| 1259 | argument now ensure that they are not called with more than one |
| 1260 | argument, making the cases shown above syntax errors. The usual |
| 1261 | behaviour of: |
| 1262 | |
| 1263 | print defined &foo, &bar, &baz; |
| 1264 | print uc "foo", "bar", "baz"; |
| 1265 | undef $foo, &bar; |
| 1266 | |
| 1267 | remains unchanged. See L<perlop>. |
| 1268 | |
| 1269 | =head2 Bit operators support full native integer width |
| 1270 | |
| 1271 | The bit operators (& | ^ ~ << >>) now operate on the full native |
| 1272 | integral width (the exact size of which is available in $Config{ivsize}). |
| 1273 | For example, if your platform is either natively 64-bit or if Perl |
| 1274 | has been configured to use 64-bit integers, these operations apply |
| 1275 | to 8 bytes (as opposed to 4 bytes on 32-bit platforms). |
| 1276 | For portability, be sure to mask off the excess bits in the result of |
| 1277 | unary C<~>, e.g., C<~$x & 0xffffffff>. |
| 1278 | |
| 1279 | =head2 Improved security features |
| 1280 | |
| 1281 | More potentially unsafe operations taint their results for improved |
| 1282 | security. |
| 1283 | |
| 1284 | The C<passwd> and C<shell> fields returned by the getpwent(), getpwnam(), |
| 1285 | and getpwuid() are now tainted, because the user can affect their own |
| 1286 | encrypted password and login shell. |
| 1287 | |
| 1288 | The variable modified by shmread(), and messages returned by msgrcv() |
| 1289 | (and its object-oriented interface IPC::SysV::Msg::rcv) are also tainted, |
| 1290 | because other untrusted processes can modify messages and shared memory |
| 1291 | segments for their own nefarious purposes. |
| 1292 | |
| 1293 | =head2 More functional bareword prototype (*) |
| 1294 | |
| 1295 | Bareword prototypes have been rationalized to enable them to be used |
| 1296 | to override builtins that accept barewords and interpret them in |
| 1297 | a special way, such as C<require> or C<do>. |
| 1298 | |
| 1299 | Arguments prototyped as C<*> will now be visible within the subroutine |
| 1300 | as either a simple scalar or as a reference to a typeglob. |
| 1301 | See L<perlsub/Prototypes>. |
| 1302 | |
| 1303 | =head2 C<require> and C<do> may be overridden |
| 1304 | |
| 1305 | C<require> and C<do 'file'> operations may be overridden locally |
| 1306 | by importing subroutines of the same name into the current package |
| 1307 | (or globally by importing them into the CORE::GLOBAL:: namespace). |
| 1308 | Overriding C<require> will also affect C<use>, provided the override |
| 1309 | is visible at compile-time. |
| 1310 | See L<perlsub/"Overriding Built-in Functions">. |
| 1311 | |
| 1312 | =head2 $^X variables may now have names longer than one character |
| 1313 | |
| 1314 | Formerly, $^X was synonymous with ${"\cX"}, but $^XY was a syntax |
| 1315 | error. Now variable names that begin with a control character may be |
| 1316 | arbitrarily long. However, for compatibility reasons, these variables |
| 1317 | I<must> be written with explicit braces, as C<${^XY}> for example. |
| 1318 | C<${^XYZ}> is synonymous with ${"\cXYZ"}. Variable names with more |
| 1319 | than one control character, such as C<${^XY^Z}>, are illegal. |
| 1320 | |
| 1321 | The old syntax has not changed. As before, `^X' may be either a |
| 1322 | literal control-X character or the two-character sequence `caret' plus |
| 1323 | `X'. When braces are omitted, the variable name stops after the |
| 1324 | control character. Thus C<"$^XYZ"> continues to be synonymous with |
| 1325 | C<$^X . "YZ"> as before. |
| 1326 | |
| 1327 | As before, lexical variables may not have names beginning with control |
| 1328 | characters. As before, variables whose names begin with a control |
| 1329 | character are always forced to be in package `main'. All such variables |
| 1330 | are reserved for future extensions, except those that begin with |
| 1331 | C<^_>, which may be used by user programs and are guaranteed not to |
| 1332 | acquire special meaning in any future version of Perl. |
| 1333 | |
| 1334 | =head2 New variable $^C reflects C<-c> switch |
| 1335 | |
| 1336 | C<$^C> has a boolean value that reflects whether perl is being run |
| 1337 | in compile-only mode (i.e. via the C<-c> switch). Since |
| 1338 | BEGIN blocks are executed under such conditions, this variable |
| 1339 | enables perl code to determine whether actions that make sense |
| 1340 | only during normal running are warranted. See L<perlvar>. |
| 1341 | |
| 1342 | =head2 New variable $^V contains Perl version as a string |
| 1343 | |
| 1344 | C<$^V> contains the Perl version number as a string composed of |
| 1345 | characters whose ordinals match the version numbers, i.e. v5.6.0. |
| 1346 | This may be used in string comparisons. |
| 1347 | |
| 1348 | See C<Support for strings represented as a vector of ordinals> for an |
| 1349 | example. |
| 1350 | |
| 1351 | =head2 Optional Y2K warnings |
| 1352 | |
| 1353 | If Perl is built with the cpp macro C<PERL_Y2KWARN> defined, |
| 1354 | it emits optional warnings when concatenating the number 19 |
| 1355 | with another number. |
| 1356 | |
| 1357 | This behavior must be specifically enabled when running Configure. |
| 1358 | See F<INSTALL> and F<README.Y2K>. |
| 1359 | |
| 1360 | =head2 Arrays now always interpolate into double-quoted strings |
| 1361 | |
| 1362 | In double-quoted strings, arrays now interpolate, no matter what. The |
| 1363 | behavior in earlier versions of perl 5 was that arrays would interpolate |
| 1364 | into strings if the array had been mentioned before the string was |
| 1365 | compiled, and otherwise Perl would raise a fatal compile-time error. |
| 1366 | In versions 5.000 through 5.003, the error was |
| 1367 | |
| 1368 | Literal @example now requires backslash |
| 1369 | |
| 1370 | In versions 5.004_01 through 5.6.0, the error was |
| 1371 | |
| 1372 | In string, @example now must be written as \@example |
| 1373 | |
| 1374 | The idea here was to get people into the habit of writing |
| 1375 | C<"fred\@example.com"> when they wanted a literal C<@> sign, just as |
| 1376 | they have always written C<"Give me back my \$5"> when they wanted a |
| 1377 | literal C<$> sign. |
| 1378 | |
| 1379 | Starting with 5.6.1, when Perl now sees an C<@> sign in a |
| 1380 | double-quoted string, it I<always> attempts to interpolate an array, |
| 1381 | regardless of whether or not the array has been used or declared |
| 1382 | already. The fatal error has been downgraded to an optional warning: |
| 1383 | |
| 1384 | Possible unintended interpolation of @example in string |
| 1385 | |
| 1386 | This warns you that C<"fred@example.com"> is going to turn into |
| 1387 | C<fred.com> if you don't backslash the C<@>. |
| 1388 | See http://www.plover.com/~mjd/perl/at-error.html for more details |
| 1389 | about the history here. |
| 1390 | |
| 1391 | =head2 @- and @+ provide starting/ending offsets of regex submatches |
| 1392 | |
| 1393 | The new magic variables @- and @+ provide the starting and ending |
| 1394 | offsets, respectively, of $&, $1, $2, etc. See L<perlvar> for |
| 1395 | details. |
| 1396 | |
| 1397 | =head1 Modules and Pragmata |
| 1398 | |
| 1399 | =head2 Modules |
| 1400 | |
| 1401 | =over 4 |
| 1402 | |
| 1403 | =item attributes |
| 1404 | |
| 1405 | While used internally by Perl as a pragma, this module also |
| 1406 | provides a way to fetch subroutine and variable attributes. |
| 1407 | See L<attributes>. |
| 1408 | |
| 1409 | =item B |
| 1410 | |
| 1411 | The Perl Compiler suite has been extensively reworked for this |
| 1412 | release. More of the standard Perl testsuite passes when run |
| 1413 | under the Compiler, but there is still a significant way to |
| 1414 | go to achieve production quality compiled executables. |
| 1415 | |
| 1416 | NOTE: The Compiler suite remains highly experimental. The |
| 1417 | generated code may not be correct, even when it manages to execute |
| 1418 | without errors. |
| 1419 | |
| 1420 | =item Benchmark |
| 1421 | |
| 1422 | Overall, Benchmark results exhibit lower average error and better timing |
| 1423 | accuracy. |
| 1424 | |
| 1425 | You can now run tests for I<n> seconds instead of guessing the right |
| 1426 | number of tests to run: e.g., timethese(-5, ...) will run each |
| 1427 | code for at least 5 CPU seconds. Zero as the "number of repetitions" |
| 1428 | means "for at least 3 CPU seconds". The output format has also |
| 1429 | changed. For example: |
| 1430 | |
| 1431 | use Benchmark;$x=3;timethese(-5,{a=>sub{$x*$x},b=>sub{$x**2}}) |
| 1432 | |
| 1433 | will now output something like this: |
| 1434 | |
| 1435 | Benchmark: running a, b, each for at least 5 CPU seconds... |
| 1436 | a: 5 wallclock secs ( 5.77 usr + 0.00 sys = 5.77 CPU) @ 200551.91/s (n=1156516) |
| 1437 | b: 4 wallclock secs ( 5.00 usr + 0.02 sys = 5.02 CPU) @ 159605.18/s (n=800686) |
| 1438 | |
| 1439 | New features: "each for at least N CPU seconds...", "wallclock secs", |
| 1440 | and the "@ operations/CPU second (n=operations)". |
| 1441 | |
| 1442 | timethese() now returns a reference to a hash of Benchmark objects containing |
| 1443 | the test results, keyed on the names of the tests. |
| 1444 | |
| 1445 | timethis() now returns the iterations field in the Benchmark result object |
| 1446 | instead of 0. |
| 1447 | |
| 1448 | timethese(), timethis(), and the new cmpthese() (see below) can also take |
| 1449 | a format specifier of 'none' to suppress output. |
| 1450 | |
| 1451 | A new function countit() is just like timeit() except that it takes a |
| 1452 | TIME instead of a COUNT. |
| 1453 | |
| 1454 | A new function cmpthese() prints a chart comparing the results of each test |
| 1455 | returned from a timethese() call. For each possible pair of tests, the |
| 1456 | percentage speed difference (iters/sec or seconds/iter) is shown. |
| 1457 | |
| 1458 | For other details, see L<Benchmark>. |
| 1459 | |
| 1460 | =item ByteLoader |
| 1461 | |
| 1462 | The ByteLoader is a dedicated extension to generate and run |
| 1463 | Perl bytecode. See L<ByteLoader>. |
| 1464 | |
| 1465 | =item constant |
| 1466 | |
| 1467 | References can now be used. |
| 1468 | |
| 1469 | The new version also allows a leading underscore in constant names, but |
| 1470 | disallows a double leading underscore (as in "__LINE__"). Some other names |
| 1471 | are disallowed or warned against, including BEGIN, END, etc. Some names |
| 1472 | which were forced into main:: used to fail silently in some cases; now they're |
| 1473 | fatal (outside of main::) and an optional warning (inside of main::). |
| 1474 | The ability to detect whether a constant had been set with a given name has |
| 1475 | been added. |
| 1476 | |
| 1477 | See L<constant>. |
| 1478 | |
| 1479 | =item charnames |
| 1480 | |
| 1481 | This pragma implements the C<\N> string escape. See L<charnames>. |
| 1482 | |
| 1483 | =item Data::Dumper |
| 1484 | |
| 1485 | A C<Maxdepth> setting can be specified to avoid venturing |
| 1486 | too deeply into deep data structures. See L<Data::Dumper>. |
| 1487 | |
| 1488 | The XSUB implementation of Dump() is now automatically called if the |
| 1489 | C<Useqq> setting is not in use. |
| 1490 | |
| 1491 | Dumping C<qr//> objects works correctly. |
| 1492 | |
| 1493 | =item DB |
| 1494 | |
| 1495 | C<DB> is an experimental module that exposes a clean abstraction |
| 1496 | to Perl's debugging API. |
| 1497 | |
| 1498 | =item DB_File |
| 1499 | |
| 1500 | DB_File can now be built with Berkeley DB versions 1, 2 or 3. |
| 1501 | See C<ext/DB_File/Changes>. |
| 1502 | |
| 1503 | =item Devel::DProf |
| 1504 | |
| 1505 | Devel::DProf, a Perl source code profiler has been added. See |
| 1506 | L<Devel::DProf> and L<dprofpp>. |
| 1507 | |
| 1508 | =item Devel::Peek |
| 1509 | |
| 1510 | The Devel::Peek module provides access to the internal representation |
| 1511 | of Perl variables and data. It is a data debugging tool for the XS programmer. |
| 1512 | |
| 1513 | =item Dumpvalue |
| 1514 | |
| 1515 | The Dumpvalue module provides screen dumps of Perl data. |
| 1516 | |
| 1517 | =item DynaLoader |
| 1518 | |
| 1519 | DynaLoader now supports a dl_unload_file() function on platforms that |
| 1520 | support unloading shared objects using dlclose(). |
| 1521 | |
| 1522 | Perl can also optionally arrange to unload all extension shared objects |
| 1523 | loaded by Perl. To enable this, build Perl with the Configure option |
| 1524 | C<-Accflags=-DDL_UNLOAD_ALL_AT_EXIT>. (This maybe useful if you are |
| 1525 | using Apache with mod_perl.) |
| 1526 | |
| 1527 | =item English |
| 1528 | |
| 1529 | $PERL_VERSION now stands for C<$^V> (a string value) rather than for C<$]> |
| 1530 | (a numeric value). |
| 1531 | |
| 1532 | =item Env |
| 1533 | |
| 1534 | Env now supports accessing environment variables like PATH as array |
| 1535 | variables. |
| 1536 | |
| 1537 | =item Fcntl |
| 1538 | |
| 1539 | More Fcntl constants added: F_SETLK64, F_SETLKW64, O_LARGEFILE for |
| 1540 | large file (more than 4GB) access (NOTE: the O_LARGEFILE is |
| 1541 | automatically added to sysopen() flags if large file support has been |
| 1542 | configured, as is the default), Free/Net/OpenBSD locking behaviour |
| 1543 | flags F_FLOCK, F_POSIX, Linux F_SHLCK, and O_ACCMODE: the combined |
| 1544 | mask of O_RDONLY, O_WRONLY, and O_RDWR. The seek()/sysseek() |
| 1545 | constants SEEK_SET, SEEK_CUR, and SEEK_END are available via the |
| 1546 | C<:seek> tag. The chmod()/stat() S_IF* constants and S_IS* functions |
| 1547 | are available via the C<:mode> tag. |
| 1548 | |
| 1549 | =item File::Compare |
| 1550 | |
| 1551 | A compare_text() function has been added, which allows custom |
| 1552 | comparison functions. See L<File::Compare>. |
| 1553 | |
| 1554 | =item File::Find |
| 1555 | |
| 1556 | File::Find now works correctly when the wanted() function is either |
| 1557 | autoloaded or is a symbolic reference. |
| 1558 | |
| 1559 | A bug that caused File::Find to lose track of the working directory |
| 1560 | when pruning top-level directories has been fixed. |
| 1561 | |
| 1562 | File::Find now also supports several other options to control its |
| 1563 | behavior. It can follow symbolic links if the C<follow> option is |
| 1564 | specified. Enabling the C<no_chdir> option will make File::Find skip |
| 1565 | changing the current directory when walking directories. The C<untaint> |
| 1566 | flag can be useful when running with taint checks enabled. |
| 1567 | |
| 1568 | See L<File::Find>. |
| 1569 | |
| 1570 | =item File::Glob |
| 1571 | |
| 1572 | This extension implements BSD-style file globbing. By default, |
| 1573 | it will also be used for the internal implementation of the glob() |
| 1574 | operator. See L<File::Glob>. |
| 1575 | |
| 1576 | =item File::Spec |
| 1577 | |
| 1578 | New methods have been added to the File::Spec module: devnull() returns |
| 1579 | the name of the null device (/dev/null on Unix) and tmpdir() the name of |
| 1580 | the temp directory (normally /tmp on Unix). There are now also methods |
| 1581 | to convert between absolute and relative filenames: abs2rel() and |
| 1582 | rel2abs(). For compatibility with operating systems that specify volume |
| 1583 | names in file paths, the splitpath(), splitdir(), and catdir() methods |
| 1584 | have been added. |
| 1585 | |
| 1586 | =item File::Spec::Functions |
| 1587 | |
| 1588 | The new File::Spec::Functions modules provides a function interface |
| 1589 | to the File::Spec module. Allows shorthand |
| 1590 | |
| 1591 | $fullname = catfile($dir1, $dir2, $file); |
| 1592 | |
| 1593 | instead of |
| 1594 | |
| 1595 | $fullname = File::Spec->catfile($dir1, $dir2, $file); |
| 1596 | |
| 1597 | =item Getopt::Long |
| 1598 | |
| 1599 | Getopt::Long licensing has changed to allow the Perl Artistic License |
| 1600 | as well as the GPL. It used to be GPL only, which got in the way of |
| 1601 | non-GPL applications that wanted to use Getopt::Long. |
| 1602 | |
| 1603 | Getopt::Long encourages the use of Pod::Usage to produce help |
| 1604 | messages. For example: |
| 1605 | |
| 1606 | use Getopt::Long; |
| 1607 | use Pod::Usage; |
| 1608 | my $man = 0; |
| 1609 | my $help = 0; |
| 1610 | GetOptions('help|?' => \$help, man => \$man) or pod2usage(2); |
| 1611 | pod2usage(1) if $help; |
| 1612 | pod2usage(-exitstatus => 0, -verbose => 2) if $man; |
| 1613 | |
| 1614 | __END__ |
| 1615 | |
| 1616 | =head1 NAME |
| 1617 | |
| 1618 | sample - Using Getopt::Long and Pod::Usage |
| 1619 | |
| 1620 | =head1 SYNOPSIS |
| 1621 | |
| 1622 | sample [options] [file ...] |
| 1623 | |
| 1624 | Options: |
| 1625 | -help brief help message |
| 1626 | -man full documentation |
| 1627 | |
| 1628 | =head1 OPTIONS |
| 1629 | |
| 1630 | =over 8 |
| 1631 | |
| 1632 | =item B<-help> |
| 1633 | |
| 1634 | Print a brief help message and exits. |
| 1635 | |
| 1636 | =item B<-man> |
| 1637 | |
| 1638 | Prints the manual page and exits. |
| 1639 | |
| 1640 | =back |
| 1641 | |
| 1642 | =head1 DESCRIPTION |
| 1643 | |
| 1644 | B<This program> will read the given input file(s) and do something |
| 1645 | useful with the contents thereof. |
| 1646 | |
| 1647 | =cut |
| 1648 | |
| 1649 | See L<Pod::Usage> for details. |
| 1650 | |
| 1651 | A bug that prevented the non-option call-back <> from being |
| 1652 | specified as the first argument has been fixed. |
| 1653 | |
| 1654 | To specify the characters < and > as option starters, use ><. Note, |
| 1655 | however, that changing option starters is strongly deprecated. |
| 1656 | |
| 1657 | =item IO |
| 1658 | |
| 1659 | write() and syswrite() will now accept a single-argument |
| 1660 | form of the call, for consistency with Perl's syswrite(). |
| 1661 | |
| 1662 | You can now create a TCP-based IO::Socket::INET without forcing |
| 1663 | a connect attempt. This allows you to configure its options |
| 1664 | (like making it non-blocking) and then call connect() manually. |
| 1665 | |
| 1666 | A bug that prevented the IO::Socket::protocol() accessor |
| 1667 | from ever returning the correct value has been corrected. |
| 1668 | |
| 1669 | IO::Socket::connect now uses non-blocking IO instead of alarm() |
| 1670 | to do connect timeouts. |
| 1671 | |
| 1672 | IO::Socket::accept now uses select() instead of alarm() for doing |
| 1673 | timeouts. |
| 1674 | |
| 1675 | IO::Socket::INET->new now sets $! correctly on failure. $@ is |
| 1676 | still set for backwards compatibility. |
| 1677 | |
| 1678 | =item JPL |
| 1679 | |
| 1680 | Java Perl Lingo is now distributed with Perl. See jpl/README |
| 1681 | for more information. |
| 1682 | |
| 1683 | =item lib |
| 1684 | |
| 1685 | C<use lib> now weeds out any trailing duplicate entries. |
| 1686 | C<no lib> removes all named entries. |
| 1687 | |
| 1688 | =item Math::BigInt |
| 1689 | |
| 1690 | The bitwise operations C<<< << >>>, C<<< >> >>>, C<&>, C<|>, |
| 1691 | and C<~> are now supported on bigints. |
| 1692 | |
| 1693 | =item Math::Complex |
| 1694 | |
| 1695 | The accessor methods Re, Im, arg, abs, rho, and theta can now also |
| 1696 | act as mutators (accessor $z->Re(), mutator $z->Re(3)). |
| 1697 | |
| 1698 | The class method C<display_format> and the corresponding object method |
| 1699 | C<display_format>, in addition to accepting just one argument, now can |
| 1700 | also accept a parameter hash. Recognized keys of a parameter hash are |
| 1701 | C<"style">, which corresponds to the old one parameter case, and two |
| 1702 | new parameters: C<"format">, which is a printf()-style format string |
| 1703 | (defaults usually to C<"%.15g">, you can revert to the default by |
| 1704 | setting the format string to C<undef>) used for both parts of a |
| 1705 | complex number, and C<"polar_pretty_print"> (defaults to true), |
| 1706 | which controls whether an attempt is made to try to recognize small |
| 1707 | multiples and rationals of pi (2pi, pi/2) at the argument (angle) of a |
| 1708 | polar complex number. |
| 1709 | |
| 1710 | The potentially disruptive change is that in list context both methods |
| 1711 | now I<return the parameter hash>, instead of only the value of the |
| 1712 | C<"style"> parameter. |
| 1713 | |
| 1714 | =item Math::Trig |
| 1715 | |
| 1716 | A little bit of radial trigonometry (cylindrical and spherical), |
| 1717 | radial coordinate conversions, and the great circle distance were added. |
| 1718 | |
| 1719 | =item Pod::Parser, Pod::InputObjects |
| 1720 | |
| 1721 | Pod::Parser is a base class for parsing and selecting sections of |
| 1722 | pod documentation from an input stream. This module takes care of |
| 1723 | identifying pod paragraphs and commands in the input and hands off the |
| 1724 | parsed paragraphs and commands to user-defined methods which are free |
| 1725 | to interpret or translate them as they see fit. |
| 1726 | |
| 1727 | Pod::InputObjects defines some input objects needed by Pod::Parser, and |
| 1728 | for advanced users of Pod::Parser that need more about a command besides |
| 1729 | its name and text. |
| 1730 | |
| 1731 | As of release 5.6.0 of Perl, Pod::Parser is now the officially sanctioned |
| 1732 | "base parser code" recommended for use by all pod2xxx translators. |
| 1733 | Pod::Text (pod2text) and Pod::Man (pod2man) have already been converted |
| 1734 | to use Pod::Parser and efforts to convert Pod::HTML (pod2html) are already |
| 1735 | underway. For any questions or comments about pod parsing and translating |
| 1736 | issues and utilities, please use the pod-people@perl.org mailing list. |
| 1737 | |
| 1738 | For further information, please see L<Pod::Parser> and L<Pod::InputObjects>. |
| 1739 | |
| 1740 | =item Pod::Checker, podchecker |
| 1741 | |
| 1742 | This utility checks pod files for correct syntax, according to |
| 1743 | L<perlpod>. Obvious errors are flagged as such, while warnings are |
| 1744 | printed for mistakes that can be handled gracefully. The checklist is |
| 1745 | not complete yet. See L<Pod::Checker>. |
| 1746 | |
| 1747 | =item Pod::ParseUtils, Pod::Find |
| 1748 | |
| 1749 | These modules provide a set of gizmos that are useful mainly for pod |
| 1750 | translators. L<Pod::Find|Pod::Find> traverses directory structures and |
| 1751 | returns found pod files, along with their canonical names (like |
| 1752 | C<File::Spec::Unix>). L<Pod::ParseUtils|Pod::ParseUtils> contains |
| 1753 | B<Pod::List> (useful for storing pod list information), B<Pod::Hyperlink> |
| 1754 | (for parsing the contents of C<LE<lt>E<gt>> sequences) and B<Pod::Cache> |
| 1755 | (for caching information about pod files, e.g., link nodes). |
| 1756 | |
| 1757 | =item Pod::Select, podselect |
| 1758 | |
| 1759 | Pod::Select is a subclass of Pod::Parser which provides a function |
| 1760 | named "podselect()" to filter out user-specified sections of raw pod |
| 1761 | documentation from an input stream. podselect is a script that provides |
| 1762 | access to Pod::Select from other scripts to be used as a filter. |
| 1763 | See L<Pod::Select>. |
| 1764 | |
| 1765 | =item Pod::Usage, pod2usage |
| 1766 | |
| 1767 | Pod::Usage provides the function "pod2usage()" to print usage messages for |
| 1768 | a Perl script based on its embedded pod documentation. The pod2usage() |
| 1769 | function is generally useful to all script authors since it lets them |
| 1770 | write and maintain a single source (the pods) for documentation, thus |
| 1771 | removing the need to create and maintain redundant usage message text |
| 1772 | consisting of information already in the pods. |
| 1773 | |
| 1774 | There is also a pod2usage script which can be used from other kinds of |
| 1775 | scripts to print usage messages from pods (even for non-Perl scripts |
| 1776 | with pods embedded in comments). |
| 1777 | |
| 1778 | For details and examples, please see L<Pod::Usage>. |
| 1779 | |
| 1780 | =item Pod::Text and Pod::Man |
| 1781 | |
| 1782 | Pod::Text has been rewritten to use Pod::Parser. While pod2text() is |
| 1783 | still available for backwards compatibility, the module now has a new |
| 1784 | preferred interface. See L<Pod::Text> for the details. The new Pod::Text |
| 1785 | module is easily subclassed for tweaks to the output, and two such |
| 1786 | subclasses (Pod::Text::Termcap for man-page-style bold and underlining |
| 1787 | using termcap information, and Pod::Text::Color for markup with ANSI color |
| 1788 | sequences) are now standard. |
| 1789 | |
| 1790 | pod2man has been turned into a module, Pod::Man, which also uses |
| 1791 | Pod::Parser. In the process, several outstanding bugs related to quotes |
| 1792 | in section headers, quoting of code escapes, and nested lists have been |
| 1793 | fixed. pod2man is now a wrapper script around this module. |
| 1794 | |
| 1795 | =item SDBM_File |
| 1796 | |
| 1797 | An EXISTS method has been added to this module (and sdbm_exists() has |
| 1798 | been added to the underlying sdbm library), so one can now call exists |
| 1799 | on an SDBM_File tied hash and get the correct result, rather than a |
| 1800 | runtime error. |
| 1801 | |
| 1802 | A bug that may have caused data loss when more than one disk block |
| 1803 | happens to be read from the database in a single FETCH() has been |
| 1804 | fixed. |
| 1805 | |
| 1806 | =item Sys::Syslog |
| 1807 | |
| 1808 | Sys::Syslog now uses XSUBs to access facilities from syslog.h so it |
| 1809 | no longer requires syslog.ph to exist. |
| 1810 | |
| 1811 | =item Sys::Hostname |
| 1812 | |
| 1813 | Sys::Hostname now uses XSUBs to call the C library's gethostname() or |
| 1814 | uname() if they exist. |
| 1815 | |
| 1816 | =item Term::ANSIColor |
| 1817 | |
| 1818 | Term::ANSIColor is a very simple module to provide easy and readable |
| 1819 | access to the ANSI color and highlighting escape sequences, supported by |
| 1820 | most ANSI terminal emulators. It is now included standard. |
| 1821 | |
| 1822 | =item Time::Local |
| 1823 | |
| 1824 | The timelocal() and timegm() functions used to silently return bogus |
| 1825 | results when the date fell outside the machine's integer range. They |
| 1826 | now consistently croak() if the date falls in an unsupported range. |
| 1827 | |
| 1828 | =item Win32 |
| 1829 | |
| 1830 | The error return value in list context has been changed for all functions |
| 1831 | that return a list of values. Previously these functions returned a list |
| 1832 | with a single element C<undef> if an error occurred. Now these functions |
| 1833 | return the empty list in these situations. This applies to the following |
| 1834 | functions: |
| 1835 | |
| 1836 | Win32::FsType |
| 1837 | Win32::GetOSVersion |
| 1838 | |
| 1839 | The remaining functions are unchanged and continue to return C<undef> on |
| 1840 | error even in list context. |
| 1841 | |
| 1842 | The Win32::SetLastError(ERROR) function has been added as a complement |
| 1843 | to the Win32::GetLastError() function. |
| 1844 | |
| 1845 | The new Win32::GetFullPathName(FILENAME) returns the full absolute |
| 1846 | pathname for FILENAME in scalar context. In list context it returns |
| 1847 | a two-element list containing the fully qualified directory name and |
| 1848 | the filename. See L<Win32>. |
| 1849 | |
| 1850 | =item XSLoader |
| 1851 | |
| 1852 | The XSLoader extension is a simpler alternative to DynaLoader. |
| 1853 | See L<XSLoader>. |
| 1854 | |
| 1855 | =item DBM Filters |
| 1856 | |
| 1857 | A new feature called "DBM Filters" has been added to all the |
| 1858 | DBM modules--DB_File, GDBM_File, NDBM_File, ODBM_File, and SDBM_File. |
| 1859 | DBM Filters add four new methods to each DBM module: |
| 1860 | |
| 1861 | filter_store_key |
| 1862 | filter_store_value |
| 1863 | filter_fetch_key |
| 1864 | filter_fetch_value |
| 1865 | |
| 1866 | These can be used to filter key-value pairs before the pairs are |
| 1867 | written to the database or just after they are read from the database. |
| 1868 | See L<perldbmfilter> for further information. |
| 1869 | |
| 1870 | =back |
| 1871 | |
| 1872 | =head2 Pragmata |
| 1873 | |
| 1874 | C<use attrs> is now obsolete, and is only provided for |
| 1875 | backward-compatibility. It's been replaced by the C<sub : attributes> |
| 1876 | syntax. See L<perlsub/"Subroutine Attributes"> and L<attributes>. |
| 1877 | |
| 1878 | Lexical warnings pragma, C<use warnings;>, to control optional warnings. |
| 1879 | See L<perllexwarn>. |
| 1880 | |
| 1881 | C<use filetest> to control the behaviour of filetests (C<-r> C<-w> |
| 1882 | ...). Currently only one subpragma implemented, "use filetest |
| 1883 | 'access';", that uses access(2) or equivalent to check permissions |
| 1884 | instead of using stat(2) as usual. This matters in filesystems |
| 1885 | where there are ACLs (access control lists): the stat(2) might lie, |
| 1886 | but access(2) knows better. |
| 1887 | |
| 1888 | The C<open> pragma can be used to specify default disciplines for |
| 1889 | handle constructors (e.g. open()) and for qx//. The two |
| 1890 | pseudo-disciplines C<:raw> and C<:crlf> are currently supported on |
| 1891 | DOS-derivative platforms (i.e. where binmode is not a no-op). |
| 1892 | See also L</"binmode() can be used to set :crlf and :raw modes">. |
| 1893 | |
| 1894 | =head1 Utility Changes |
| 1895 | |
| 1896 | =head2 dprofpp |
| 1897 | |
| 1898 | C<dprofpp> is used to display profile data generated using C<Devel::DProf>. |
| 1899 | See L<dprofpp>. |
| 1900 | |
| 1901 | =head2 find2perl |
| 1902 | |
| 1903 | The C<find2perl> utility now uses the enhanced features of the File::Find |
| 1904 | module. The -depth and -follow options are supported. Pod documentation |
| 1905 | is also included in the script. |
| 1906 | |
| 1907 | =head2 h2xs |
| 1908 | |
| 1909 | The C<h2xs> tool can now work in conjunction with C<C::Scan> (available |
| 1910 | from CPAN) to automatically parse real-life header files. The C<-M>, |
| 1911 | C<-a>, C<-k>, and C<-o> options are new. |
| 1912 | |
| 1913 | =head2 perlcc |
| 1914 | |
| 1915 | C<perlcc> now supports the C and Bytecode backends. By default, |
| 1916 | it generates output from the simple C backend rather than the |
| 1917 | optimized C backend. |
| 1918 | |
| 1919 | Support for non-Unix platforms has been improved. |
| 1920 | |
| 1921 | =head2 perldoc |
| 1922 | |
| 1923 | C<perldoc> has been reworked to avoid possible security holes. |
| 1924 | It will not by default let itself be run as the superuser, but you |
| 1925 | may still use the B<-U> switch to try to make it drop privileges |
| 1926 | first. |
| 1927 | |
| 1928 | =head2 The Perl Debugger |
| 1929 | |
| 1930 | Many bug fixes and enhancements were added to F<perl5db.pl>, the |
| 1931 | Perl debugger. The help documentation was rearranged. New commands |
| 1932 | include C<< < ? >>, C<< > ? >>, and C<< { ? >> to list out current |
| 1933 | actions, C<man I<docpage>> to run your doc viewer on some perl |
| 1934 | docset, and support for quoted options. The help information was |
| 1935 | rearranged, and should be viewable once again if you're using B<less> |
| 1936 | as your pager. A serious security hole was plugged--you should |
| 1937 | immediately remove all older versions of the Perl debugger as |
| 1938 | installed in previous releases, all the way back to perl3, from |
| 1939 | your system to avoid being bitten by this. |
| 1940 | |
| 1941 | =head1 Improved Documentation |
| 1942 | |
| 1943 | Many of the platform-specific README files are now part of the perl |
| 1944 | installation. See L<perl> for the complete list. |
| 1945 | |
| 1946 | =over 4 |
| 1947 | |
| 1948 | =item perlapi.pod |
| 1949 | |
| 1950 | The official list of public Perl API functions. |
| 1951 | |
| 1952 | =item perlboot.pod |
| 1953 | |
| 1954 | A tutorial for beginners on object-oriented Perl. |
| 1955 | |
| 1956 | =item perlcompile.pod |
| 1957 | |
| 1958 | An introduction to using the Perl Compiler suite. |
| 1959 | |
| 1960 | =item perldbmfilter.pod |
| 1961 | |
| 1962 | A howto document on using the DBM filter facility. |
| 1963 | |
| 1964 | =item perldebug.pod |
| 1965 | |
| 1966 | All material unrelated to running the Perl debugger, plus all |
| 1967 | low-level guts-like details that risked crushing the casual user |
| 1968 | of the debugger, have been relocated from the old manpage to the |
| 1969 | next entry below. |
| 1970 | |
| 1971 | =item perldebguts.pod |
| 1972 | |
| 1973 | This new manpage contains excessively low-level material not related |
| 1974 | to the Perl debugger, but slightly related to debugging Perl itself. |
| 1975 | It also contains some arcane internal details of how the debugging |
| 1976 | process works that may only be of interest to developers of Perl |
| 1977 | debuggers. |
| 1978 | |
| 1979 | =item perlfork.pod |
| 1980 | |
| 1981 | Notes on the fork() emulation currently available for the Windows platform. |
| 1982 | |
| 1983 | =item perlfilter.pod |
| 1984 | |
| 1985 | An introduction to writing Perl source filters. |
| 1986 | |
| 1987 | =item perlhack.pod |
| 1988 | |
| 1989 | Some guidelines for hacking the Perl source code. |
| 1990 | |
| 1991 | =item perlintern.pod |
| 1992 | |
| 1993 | A list of internal functions in the Perl source code. |
| 1994 | (List is currently empty.) |
| 1995 | |
| 1996 | =item perllexwarn.pod |
| 1997 | |
| 1998 | Introduction and reference information about lexically scoped |
| 1999 | warning categories. |
| 2000 | |
| 2001 | =item perlnumber.pod |
| 2002 | |
| 2003 | Detailed information about numbers as they are represented in Perl. |
| 2004 | |
| 2005 | =item perlopentut.pod |
| 2006 | |
| 2007 | A tutorial on using open() effectively. |
| 2008 | |
| 2009 | =item perlreftut.pod |
| 2010 | |
| 2011 | A tutorial that introduces the essentials of references. |
| 2012 | |
| 2013 | =item perltootc.pod |
| 2014 | |
| 2015 | A tutorial on managing class data for object modules. |
| 2016 | |
| 2017 | =item perltodo.pod |
| 2018 | |
| 2019 | Discussion of the most often wanted features that may someday be |
| 2020 | supported in Perl. |
| 2021 | |
| 2022 | =item perlunicode.pod |
| 2023 | |
| 2024 | An introduction to Unicode support features in Perl. |
| 2025 | |
| 2026 | =back |
| 2027 | |
| 2028 | =head1 Performance enhancements |
| 2029 | |
| 2030 | =head2 Simple sort() using { $a <=> $b } and the like are optimized |
| 2031 | |
| 2032 | Many common sort() operations using a simple inlined block are now |
| 2033 | optimized for faster performance. |
| 2034 | |
| 2035 | =head2 Optimized assignments to lexical variables |
| 2036 | |
| 2037 | Certain operations in the RHS of assignment statements have been |
| 2038 | optimized to directly set the lexical variable on the LHS, |
| 2039 | eliminating redundant copying overheads. |
| 2040 | |
| 2041 | =head2 Faster subroutine calls |
| 2042 | |
| 2043 | Minor changes in how subroutine calls are handled internally |
| 2044 | provide marginal improvements in performance. |
| 2045 | |
| 2046 | =head2 delete(), each(), values() and hash iteration are faster |
| 2047 | |
| 2048 | The hash values returned by delete(), each(), values() and hashes in a |
| 2049 | list context are the actual values in the hash, instead of copies. |
| 2050 | This results in significantly better performance, because it eliminates |
| 2051 | needless copying in most situations. |
| 2052 | |
| 2053 | =head1 Installation and Configuration Improvements |
| 2054 | |
| 2055 | =head2 -Dusethreads means something different |
| 2056 | |
| 2057 | The -Dusethreads flag now enables the experimental interpreter-based thread |
| 2058 | support by default. To get the flavor of experimental threads that was in |
| 2059 | 5.005 instead, you need to run Configure with "-Dusethreads -Duse5005threads". |
| 2060 | |
| 2061 | As of v5.6.0, interpreter-threads support is still lacking a way to |
| 2062 | create new threads from Perl (i.e., C<use Thread;> will not work with |
| 2063 | interpreter threads). C<use Thread;> continues to be available when you |
| 2064 | specify the -Duse5005threads option to Configure, bugs and all. |
| 2065 | |
| 2066 | NOTE: Support for threads continues to be an experimental feature. |
| 2067 | Interfaces and implementation are subject to sudden and drastic changes. |
| 2068 | |
| 2069 | =head2 New Configure flags |
| 2070 | |
| 2071 | The following new flags may be enabled on the Configure command line |
| 2072 | by running Configure with C<-Dflag>. |
| 2073 | |
| 2074 | usemultiplicity |
| 2075 | usethreads useithreads (new interpreter threads: no Perl API yet) |
| 2076 | usethreads use5005threads (threads as they were in 5.005) |
| 2077 | |
| 2078 | use64bitint (equal to now deprecated 'use64bits') |
| 2079 | use64bitall |
| 2080 | |
| 2081 | uselongdouble |
| 2082 | usemorebits |
| 2083 | uselargefiles |
| 2084 | usesocks (only SOCKS v5 supported) |
| 2085 | |
| 2086 | =head2 Threadedness and 64-bitness now more daring |
| 2087 | |
| 2088 | The Configure options enabling the use of threads and the use of |
| 2089 | 64-bitness are now more daring in the sense that they no more have an |
| 2090 | explicit list of operating systems of known threads/64-bit |
| 2091 | capabilities. In other words: if your operating system has the |
| 2092 | necessary APIs and datatypes, you should be able just to go ahead and |
| 2093 | use them, for threads by Configure -Dusethreads, and for 64 bits |
| 2094 | either explicitly by Configure -Duse64bitint or implicitly if your |
| 2095 | system has 64-bit wide datatypes. See also L<"64-bit support">. |
| 2096 | |
| 2097 | =head2 Long Doubles |
| 2098 | |
| 2099 | Some platforms have "long doubles", floating point numbers of even |
| 2100 | larger range than ordinary "doubles". To enable using long doubles for |
| 2101 | Perl's scalars, use -Duselongdouble. |
| 2102 | |
| 2103 | =head2 -Dusemorebits |
| 2104 | |
| 2105 | You can enable both -Duse64bitint and -Duselongdouble with -Dusemorebits. |
| 2106 | See also L<"64-bit support">. |
| 2107 | |
| 2108 | =head2 -Duselargefiles |
| 2109 | |
| 2110 | Some platforms support system APIs that are capable of handling large files |
| 2111 | (typically, files larger than two gigabytes). Perl will try to use these |
| 2112 | APIs if you ask for -Duselargefiles. |
| 2113 | |
| 2114 | See L<"Large file support"> for more information. |
| 2115 | |
| 2116 | =head2 installusrbinperl |
| 2117 | |
| 2118 | You can use "Configure -Uinstallusrbinperl" which causes installperl |
| 2119 | to skip installing perl also as /usr/bin/perl. This is useful if you |
| 2120 | prefer not to modify /usr/bin for some reason or another but harmful |
| 2121 | because many scripts assume to find Perl in /usr/bin/perl. |
| 2122 | |
| 2123 | =head2 SOCKS support |
| 2124 | |
| 2125 | You can use "Configure -Dusesocks" which causes Perl to probe |
| 2126 | for the SOCKS proxy protocol library (v5, not v4). For more information |
| 2127 | on SOCKS, see: |
| 2128 | |
| 2129 | http://www.socks.nec.com/ |
| 2130 | |
| 2131 | =head2 C<-A> flag |
| 2132 | |
| 2133 | You can "post-edit" the Configure variables using the Configure C<-A> |
| 2134 | switch. The editing happens immediately after the platform specific |
| 2135 | hints files have been processed but before the actual configuration |
| 2136 | process starts. Run C<Configure -h> to find out the full C<-A> syntax. |
| 2137 | |
| 2138 | =head2 Enhanced Installation Directories |
| 2139 | |
| 2140 | The installation structure has been enriched to improve the support |
| 2141 | for maintaining multiple versions of perl, to provide locations for |
| 2142 | vendor-supplied modules, scripts, and manpages, and to ease maintenance |
| 2143 | of locally-added modules, scripts, and manpages. See the section on |
| 2144 | Installation Directories in the INSTALL file for complete details. |
| 2145 | For most users building and installing from source, the defaults should |
| 2146 | be fine. |
| 2147 | |
| 2148 | If you previously used C<Configure -Dsitelib> or C<-Dsitearch> to set |
| 2149 | special values for library directories, you might wish to consider using |
| 2150 | the new C<-Dsiteprefix> setting instead. Also, if you wish to re-use a |
| 2151 | config.sh file from an earlier version of perl, you should be sure to |
| 2152 | check that Configure makes sensible choices for the new directories. |
| 2153 | See INSTALL for complete details. |
| 2154 | |
| 2155 | =head2 gcc automatically tried if 'cc' does not seem to be working |
| 2156 | |
| 2157 | In many platforms the vendor-supplied 'cc' is too stripped-down to |
| 2158 | build Perl (basically, the 'cc' doesn't do ANSI C). If this seems |
| 2159 | to be the case and the 'cc' does not seem to be the GNU C compiler |
| 2160 | 'gcc', an automatic attempt is made to find and use 'gcc' instead. |
| 2161 | |
| 2162 | =head1 Platform specific changes |
| 2163 | |
| 2164 | =head2 Supported platforms |
| 2165 | |
| 2166 | =over 4 |
| 2167 | |
| 2168 | =item * |
| 2169 | |
| 2170 | The Mach CThreads (NEXTSTEP, OPENSTEP) are now supported by the Thread |
| 2171 | extension. |
| 2172 | |
| 2173 | =item * |
| 2174 | |
| 2175 | GNU/Hurd is now supported. |
| 2176 | |
| 2177 | =item * |
| 2178 | |
| 2179 | Rhapsody/Darwin is now supported. |
| 2180 | |
| 2181 | =item * |
| 2182 | |
| 2183 | EPOC is now supported (on Psion 5). |
| 2184 | |
| 2185 | =item * |
| 2186 | |
| 2187 | The cygwin port (formerly cygwin32) has been greatly improved. |
| 2188 | |
| 2189 | =back |
| 2190 | |
| 2191 | =head2 DOS |
| 2192 | |
| 2193 | =over 4 |
| 2194 | |
| 2195 | =item * |
| 2196 | |
| 2197 | Perl now works with djgpp 2.02 (and 2.03 alpha). |
| 2198 | |
| 2199 | =item * |
| 2200 | |
| 2201 | Environment variable names are not converted to uppercase any more. |
| 2202 | |
| 2203 | =item * |
| 2204 | |
| 2205 | Incorrect exit codes from backticks have been fixed. |
| 2206 | |
| 2207 | =item * |
| 2208 | |
| 2209 | This port continues to use its own builtin globbing (not File::Glob). |
| 2210 | |
| 2211 | =back |
| 2212 | |
| 2213 | =head2 OS390 (OpenEdition MVS) |
| 2214 | |
| 2215 | Support for this EBCDIC platform has not been renewed in this release. |
| 2216 | There are difficulties in reconciling Perl's standardization on UTF-8 |
| 2217 | as its internal representation for characters with the EBCDIC character |
| 2218 | set, because the two are incompatible. |
| 2219 | |
| 2220 | It is unclear whether future versions will renew support for this |
| 2221 | platform, but the possibility exists. |
| 2222 | |
| 2223 | =head2 VMS |
| 2224 | |
| 2225 | Numerous revisions and extensions to configuration, build, testing, and |
| 2226 | installation process to accommodate core changes and VMS-specific options. |
| 2227 | |
| 2228 | Expand %ENV-handling code to allow runtime mapping to logical names, |
| 2229 | CLI symbols, and CRTL environ array. |
| 2230 | |
| 2231 | Extension of subprocess invocation code to accept filespecs as command |
| 2232 | "verbs". |
| 2233 | |
| 2234 | Add to Perl command line processing the ability to use default file types and |
| 2235 | to recognize Unix-style C<2E<gt>&1>. |
| 2236 | |
| 2237 | Expansion of File::Spec::VMS routines, and integration into ExtUtils::MM_VMS. |
| 2238 | |
| 2239 | Extension of ExtUtils::MM_VMS to handle complex extensions more flexibly. |
| 2240 | |
| 2241 | Barewords at start of Unix-syntax paths may be treated as text rather than |
| 2242 | only as logical names. |
| 2243 | |
| 2244 | Optional secure translation of several logical names used internally by Perl. |
| 2245 | |
| 2246 | Miscellaneous bugfixing and porting of new core code to VMS. |
| 2247 | |
| 2248 | Thanks are gladly extended to the many people who have contributed VMS |
| 2249 | patches, testing, and ideas. |
| 2250 | |
| 2251 | =head2 Win32 |
| 2252 | |
| 2253 | Perl can now emulate fork() internally, using multiple interpreters running |
| 2254 | in different concurrent threads. This support must be enabled at build |
| 2255 | time. See L<perlfork> for detailed information. |
| 2256 | |
| 2257 | When given a pathname that consists only of a drivename, such as C<A:>, |
| 2258 | opendir() and stat() now use the current working directory for the drive |
| 2259 | rather than the drive root. |
| 2260 | |
| 2261 | The builtin XSUB functions in the Win32:: namespace are documented. See |
| 2262 | L<Win32>. |
| 2263 | |
| 2264 | $^X now contains the full path name of the running executable. |
| 2265 | |
| 2266 | A Win32::GetLongPathName() function is provided to complement |
| 2267 | Win32::GetFullPathName() and Win32::GetShortPathName(). See L<Win32>. |
| 2268 | |
| 2269 | POSIX::uname() is supported. |
| 2270 | |
| 2271 | system(1,...) now returns true process IDs rather than process |
| 2272 | handles. kill() accepts any real process id, rather than strictly |
| 2273 | return values from system(1,...). |
| 2274 | |
| 2275 | For better compatibility with Unix, C<kill(0, $pid)> can now be used to |
| 2276 | test whether a process exists. |
| 2277 | |
| 2278 | The C<Shell> module is supported. |
| 2279 | |
| 2280 | Better support for building Perl under command.com in Windows 95 |
| 2281 | has been added. |
| 2282 | |
| 2283 | Scripts are read in binary mode by default to allow ByteLoader (and |
| 2284 | the filter mechanism in general) to work properly. For compatibility, |
| 2285 | the DATA filehandle will be set to text mode if a carriage return is |
| 2286 | detected at the end of the line containing the __END__ or __DATA__ |
| 2287 | token; if not, the DATA filehandle will be left open in binary mode. |
| 2288 | Earlier versions always opened the DATA filehandle in text mode. |
| 2289 | |
| 2290 | The glob() operator is implemented via the C<File::Glob> extension, |
| 2291 | which supports glob syntax of the C shell. This increases the flexibility |
| 2292 | of the glob() operator, but there may be compatibility issues for |
| 2293 | programs that relied on the older globbing syntax. If you want to |
| 2294 | preserve compatibility with the older syntax, you might want to run |
| 2295 | perl with C<-MFile::DosGlob>. For details and compatibility information, |
| 2296 | see L<File::Glob>. |
| 2297 | |
| 2298 | =head1 Significant bug fixes |
| 2299 | |
| 2300 | =head2 <HANDLE> on empty files |
| 2301 | |
| 2302 | With C<$/> set to C<undef>, "slurping" an empty file returns a string of |
| 2303 | zero length (instead of C<undef>, as it used to) the first time the |
| 2304 | HANDLE is read after C<$/> is set to C<undef>. Further reads yield |
| 2305 | C<undef>. |
| 2306 | |
| 2307 | This means that the following will append "foo" to an empty file (it used |
| 2308 | to do nothing): |
| 2309 | |
| 2310 | perl -0777 -pi -e 's/^/foo/' empty_file |
| 2311 | |
| 2312 | The behaviour of: |
| 2313 | |
| 2314 | perl -pi -e 's/^/foo/' empty_file |
| 2315 | |
| 2316 | is unchanged (it continues to leave the file empty). |
| 2317 | |
| 2318 | =head2 C<eval '...'> improvements |
| 2319 | |
| 2320 | Line numbers (as reflected by caller() and most diagnostics) within |
| 2321 | C<eval '...'> were often incorrect where here documents were involved. |
| 2322 | This has been corrected. |
| 2323 | |
| 2324 | Lexical lookups for variables appearing in C<eval '...'> within |
| 2325 | functions that were themselves called within an C<eval '...'> were |
| 2326 | searching the wrong place for lexicals. The lexical search now |
| 2327 | correctly ends at the subroutine's block boundary. |
| 2328 | |
| 2329 | The use of C<return> within C<eval {...}> caused $@ not to be reset |
| 2330 | correctly when no exception occurred within the eval. This has |
| 2331 | been fixed. |
| 2332 | |
| 2333 | Parsing of here documents used to be flawed when they appeared as |
| 2334 | the replacement expression in C<eval 's/.../.../e'>. This has |
| 2335 | been fixed. |
| 2336 | |
| 2337 | =head2 All compilation errors are true errors |
| 2338 | |
| 2339 | Some "errors" encountered at compile time were by necessity |
| 2340 | generated as warnings followed by eventual termination of the |
| 2341 | program. This enabled more such errors to be reported in a |
| 2342 | single run, rather than causing a hard stop at the first error |
| 2343 | that was encountered. |
| 2344 | |
| 2345 | The mechanism for reporting such errors has been reimplemented |
| 2346 | to queue compile-time errors and report them at the end of the |
| 2347 | compilation as true errors rather than as warnings. This fixes |
| 2348 | cases where error messages leaked through in the form of warnings |
| 2349 | when code was compiled at run time using C<eval STRING>, and |
| 2350 | also allows such errors to be reliably trapped using C<eval "...">. |
| 2351 | |
| 2352 | =head2 Implicitly closed filehandles are safer |
| 2353 | |
| 2354 | Sometimes implicitly closed filehandles (as when they are localized, |
| 2355 | and Perl automatically closes them on exiting the scope) could |
| 2356 | inadvertently set $? or $!. This has been corrected. |
| 2357 | |
| 2358 | |
| 2359 | =head2 Behavior of list slices is more consistent |
| 2360 | |
| 2361 | When taking a slice of a literal list (as opposed to a slice of |
| 2362 | an array or hash), Perl used to return an empty list if the |
| 2363 | result happened to be composed of all undef values. |
| 2364 | |
| 2365 | The new behavior is to produce an empty list if (and only if) |
| 2366 | the original list was empty. Consider the following example: |
| 2367 | |
| 2368 | @a = (1,undef,undef,2)[2,1,2]; |
| 2369 | |
| 2370 | The old behavior would have resulted in @a having no elements. |
| 2371 | The new behavior ensures it has three undefined elements. |
| 2372 | |
| 2373 | Note in particular that the behavior of slices of the following |
| 2374 | cases remains unchanged: |
| 2375 | |
| 2376 | @a = ()[1,2]; |
| 2377 | @a = (getpwent)[7,0]; |
| 2378 | @a = (anything_returning_empty_list())[2,1,2]; |
| 2379 | @a = @b[2,1,2]; |
| 2380 | @a = @c{'a','b','c'}; |
| 2381 | |
| 2382 | See L<perldata>. |
| 2383 | |
| 2384 | =head2 C<(\$)> prototype and C<$foo{a}> |
| 2385 | |
| 2386 | A scalar reference prototype now correctly allows a hash or |
| 2387 | array element in that slot. |
| 2388 | |
| 2389 | =head2 C<goto &sub> and AUTOLOAD |
| 2390 | |
| 2391 | The C<goto &sub> construct works correctly when C<&sub> happens |
| 2392 | to be autoloaded. |
| 2393 | |
| 2394 | =head2 C<-bareword> allowed under C<use integer> |
| 2395 | |
| 2396 | The autoquoting of barewords preceded by C<-> did not work |
| 2397 | in prior versions when the C<integer> pragma was enabled. |
| 2398 | This has been fixed. |
| 2399 | |
| 2400 | =head2 Failures in DESTROY() |
| 2401 | |
| 2402 | When code in a destructor threw an exception, it went unnoticed |
| 2403 | in earlier versions of Perl, unless someone happened to be |
| 2404 | looking in $@ just after the point the destructor happened to |
| 2405 | run. Such failures are now visible as warnings when warnings are |
| 2406 | enabled. |
| 2407 | |
| 2408 | =head2 Locale bugs fixed |
| 2409 | |
| 2410 | printf() and sprintf() previously reset the numeric locale |
| 2411 | back to the default "C" locale. This has been fixed. |
| 2412 | |
| 2413 | Numbers formatted according to the local numeric locale |
| 2414 | (such as using a decimal comma instead of a decimal dot) caused |
| 2415 | "isn't numeric" warnings, even while the operations accessing |
| 2416 | those numbers produced correct results. These warnings have been |
| 2417 | discontinued. |
| 2418 | |
| 2419 | =head2 Memory leaks |
| 2420 | |
| 2421 | The C<eval 'return sub {...}'> construct could sometimes leak |
| 2422 | memory. This has been fixed. |
| 2423 | |
| 2424 | Operations that aren't filehandle constructors used to leak memory |
| 2425 | when used on invalid filehandles. This has been fixed. |
| 2426 | |
| 2427 | Constructs that modified C<@_> could fail to deallocate values |
| 2428 | in C<@_> and thus leak memory. This has been corrected. |
| 2429 | |
| 2430 | =head2 Spurious subroutine stubs after failed subroutine calls |
| 2431 | |
| 2432 | Perl could sometimes create empty subroutine stubs when a |
| 2433 | subroutine was not found in the package. Such cases stopped |
| 2434 | later method lookups from progressing into base packages. |
| 2435 | This has been corrected. |
| 2436 | |
| 2437 | =head2 Taint failures under C<-U> |
| 2438 | |
| 2439 | When running in unsafe mode, taint violations could sometimes |
| 2440 | cause silent failures. This has been fixed. |
| 2441 | |
| 2442 | =head2 END blocks and the C<-c> switch |
| 2443 | |
| 2444 | Prior versions used to run BEGIN B<and> END blocks when Perl was |
| 2445 | run in compile-only mode. Since this is typically not the expected |
| 2446 | behavior, END blocks are not executed anymore when the C<-c> switch |
| 2447 | is used, or if compilation fails. |
| 2448 | |
| 2449 | See L</"Support for CHECK blocks"> for how to run things when the compile |
| 2450 | phase ends. |
| 2451 | |
| 2452 | =head2 Potential to leak DATA filehandles |
| 2453 | |
| 2454 | Using the C<__DATA__> token creates an implicit filehandle to |
| 2455 | the file that contains the token. It is the program's |
| 2456 | responsibility to close it when it is done reading from it. |
| 2457 | |
| 2458 | This caveat is now better explained in the documentation. |
| 2459 | See L<perldata>. |
| 2460 | |
| 2461 | =head1 New or Changed Diagnostics |
| 2462 | |
| 2463 | =over 4 |
| 2464 | |
| 2465 | =item "%s" variable %s masks earlier declaration in same %s |
| 2466 | |
| 2467 | (W misc) A "my" or "our" variable has been redeclared in the current scope or statement, |
| 2468 | effectively eliminating all access to the previous instance. This is almost |
| 2469 | always a typographical error. Note that the earlier variable will still exist |
| 2470 | until the end of the scope or until all closure referents to it are |
| 2471 | destroyed. |
| 2472 | |
| 2473 | =item "my sub" not yet implemented |
| 2474 | |
| 2475 | (F) Lexically scoped subroutines are not yet implemented. Don't try that |
| 2476 | yet. |
| 2477 | |
| 2478 | =item "our" variable %s redeclared |
| 2479 | |
| 2480 | (W misc) You seem to have already declared the same global once before in the |
| 2481 | current lexical scope. |
| 2482 | |
| 2483 | =item '!' allowed only after types %s |
| 2484 | |
| 2485 | (F) The '!' is allowed in pack() and unpack() only after certain types. |
| 2486 | See L<perlfunc/pack>. |
| 2487 | |
| 2488 | =item / cannot take a count |
| 2489 | |
| 2490 | (F) You had an unpack template indicating a counted-length string, |
| 2491 | but you have also specified an explicit size for the string. |
| 2492 | See L<perlfunc/pack>. |
| 2493 | |
| 2494 | =item / must be followed by a, A or Z |
| 2495 | |
| 2496 | (F) You had an unpack template indicating a counted-length string, |
| 2497 | which must be followed by one of the letters a, A or Z |
| 2498 | to indicate what sort of string is to be unpacked. |
| 2499 | See L<perlfunc/pack>. |
| 2500 | |
| 2501 | =item / must be followed by a*, A* or Z* |
| 2502 | |
| 2503 | (F) You had a pack template indicating a counted-length string, |
| 2504 | Currently the only things that can have their length counted are a*, A* or Z*. |
| 2505 | See L<perlfunc/pack>. |
| 2506 | |
| 2507 | =item / must follow a numeric type |
| 2508 | |
| 2509 | (F) You had an unpack template that contained a '#', |
| 2510 | but this did not follow some numeric unpack specification. |
| 2511 | See L<perlfunc/pack>. |
| 2512 | |
| 2513 | =item /%s/: Unrecognized escape \\%c passed through |
| 2514 | |
| 2515 | (W regexp) You used a backslash-character combination which is not recognized |
| 2516 | by Perl. This combination appears in an interpolated variable or a |
| 2517 | C<'>-delimited regular expression. The character was understood literally. |
| 2518 | |
| 2519 | =item /%s/: Unrecognized escape \\%c in character class passed through |
| 2520 | |
| 2521 | (W regexp) You used a backslash-character combination which is not recognized |
| 2522 | by Perl inside character classes. The character was understood literally. |
| 2523 | |
| 2524 | =item /%s/ should probably be written as "%s" |
| 2525 | |
| 2526 | (W syntax) You have used a pattern where Perl expected to find a string, |
| 2527 | as in the first argument to C<join>. Perl will treat the true |
| 2528 | or false result of matching the pattern against $_ as the string, |
| 2529 | which is probably not what you had in mind. |
| 2530 | |
| 2531 | =item %s() called too early to check prototype |
| 2532 | |
| 2533 | (W prototype) You've called a function that has a prototype before the parser saw a |
| 2534 | definition or declaration for it, and Perl could not check that the call |
| 2535 | conforms to the prototype. You need to either add an early prototype |
| 2536 | declaration for the subroutine in question, or move the subroutine |
| 2537 | definition ahead of the call to get proper prototype checking. Alternatively, |
| 2538 | if you are certain that you're calling the function correctly, you may put |
| 2539 | an ampersand before the name to avoid the warning. See L<perlsub>. |
| 2540 | |
| 2541 | =item %s argument is not a HASH or ARRAY element |
| 2542 | |
| 2543 | (F) The argument to exists() must be a hash or array element, such as: |
| 2544 | |
| 2545 | $foo{$bar} |
| 2546 | $ref->{"susie"}[12] |
| 2547 | |
| 2548 | =item %s argument is not a HASH or ARRAY element or slice |
| 2549 | |
| 2550 | (F) The argument to delete() must be either a hash or array element, such as: |
| 2551 | |
| 2552 | $foo{$bar} |
| 2553 | $ref->{"susie"}[12] |
| 2554 | |
| 2555 | or a hash or array slice, such as: |
| 2556 | |
| 2557 | @foo[$bar, $baz, $xyzzy] |
| 2558 | @{$ref->[12]}{"susie", "queue"} |
| 2559 | |
| 2560 | =item %s argument is not a subroutine name |
| 2561 | |
| 2562 | (F) The argument to exists() for C<exists &sub> must be a subroutine |
| 2563 | name, and not a subroutine call. C<exists &sub()> will generate this error. |
| 2564 | |
| 2565 | =item %s package attribute may clash with future reserved word: %s |
| 2566 | |
| 2567 | (W reserved) A lowercase attribute name was used that had a package-specific handler. |
| 2568 | That name might have a meaning to Perl itself some day, even though it |
| 2569 | doesn't yet. Perhaps you should use a mixed-case attribute name, instead. |
| 2570 | See L<attributes>. |
| 2571 | |
| 2572 | =item (in cleanup) %s |
| 2573 | |
| 2574 | (W misc) This prefix usually indicates that a DESTROY() method raised |
| 2575 | the indicated exception. Since destructors are usually called by |
| 2576 | the system at arbitrary points during execution, and often a vast |
| 2577 | number of times, the warning is issued only once for any number |
| 2578 | of failures that would otherwise result in the same message being |
| 2579 | repeated. |
| 2580 | |
| 2581 | Failure of user callbacks dispatched using the C<G_KEEPERR> flag |
| 2582 | could also result in this warning. See L<perlcall/G_KEEPERR>. |
| 2583 | |
| 2584 | =item <> should be quotes |
| 2585 | |
| 2586 | (F) You wrote C<< require <file> >> when you should have written |
| 2587 | C<require 'file'>. |
| 2588 | |
| 2589 | =item Attempt to join self |
| 2590 | |
| 2591 | (F) You tried to join a thread from within itself, which is an |
| 2592 | impossible task. You may be joining the wrong thread, or you may |
| 2593 | need to move the join() to some other thread. |
| 2594 | |
| 2595 | =item Bad evalled substitution pattern |
| 2596 | |
| 2597 | (F) You've used the /e switch to evaluate the replacement for a |
| 2598 | substitution, but perl found a syntax error in the code to evaluate, |
| 2599 | most likely an unexpected right brace '}'. |
| 2600 | |
| 2601 | =item Bad realloc() ignored |
| 2602 | |
| 2603 | (S) An internal routine called realloc() on something that had never been |
| 2604 | malloc()ed in the first place. Mandatory, but can be disabled by |
| 2605 | setting environment variable C<PERL_BADFREE> to 1. |
| 2606 | |
| 2607 | =item Bareword found in conditional |
| 2608 | |
| 2609 | (W bareword) The compiler found a bareword where it expected a conditional, |
| 2610 | which often indicates that an || or && was parsed as part of the |
| 2611 | last argument of the previous construct, for example: |
| 2612 | |
| 2613 | open FOO || die; |
| 2614 | |
| 2615 | It may also indicate a misspelled constant that has been interpreted |
| 2616 | as a bareword: |
| 2617 | |
| 2618 | use constant TYPO => 1; |
| 2619 | if (TYOP) { print "foo" } |
| 2620 | |
| 2621 | The C<strict> pragma is useful in avoiding such errors. |
| 2622 | |
| 2623 | =item Binary number > 0b11111111111111111111111111111111 non-portable |
| 2624 | |
| 2625 | (W portable) The binary number you specified is larger than 2**32-1 |
| 2626 | (4294967295) and therefore non-portable between systems. See |
| 2627 | L<perlport> for more on portability concerns. |
| 2628 | |
| 2629 | =item Bit vector size > 32 non-portable |
| 2630 | |
| 2631 | (W portable) Using bit vector sizes larger than 32 is non-portable. |
| 2632 | |
| 2633 | =item Buffer overflow in prime_env_iter: %s |
| 2634 | |
| 2635 | (W internal) A warning peculiar to VMS. While Perl was preparing to iterate over |
| 2636 | %ENV, it encountered a logical name or symbol definition which was too long, |
| 2637 | so it was truncated to the string shown. |
| 2638 | |
| 2639 | =item Can't check filesystem of script "%s" |
| 2640 | |
| 2641 | (P) For some reason you can't check the filesystem of the script for nosuid. |
| 2642 | |
| 2643 | =item Can't declare class for non-scalar %s in "%s" |
| 2644 | |
| 2645 | (S) Currently, only scalar variables can declared with a specific class |
| 2646 | qualifier in a "my" or "our" declaration. The semantics may be extended |
| 2647 | for other types of variables in future. |
| 2648 | |
| 2649 | =item Can't declare %s in "%s" |
| 2650 | |
| 2651 | (F) Only scalar, array, and hash variables may be declared as "my" or |
| 2652 | "our" variables. They must have ordinary identifiers as names. |
| 2653 | |
| 2654 | =item Can't ignore signal CHLD, forcing to default |
| 2655 | |
| 2656 | (W signal) Perl has detected that it is being run with the SIGCHLD signal |
| 2657 | (sometimes known as SIGCLD) disabled. Since disabling this signal |
| 2658 | will interfere with proper determination of exit status of child |
| 2659 | processes, Perl has reset the signal to its default value. |
| 2660 | This situation typically indicates that the parent program under |
| 2661 | which Perl may be running (e.g., cron) is being very careless. |
| 2662 | |
| 2663 | =item Can't modify non-lvalue subroutine call |
| 2664 | |
| 2665 | (F) Subroutines meant to be used in lvalue context should be declared as |
| 2666 | such, see L<perlsub/"Lvalue subroutines">. |
| 2667 | |
| 2668 | =item Can't read CRTL environ |
| 2669 | |
| 2670 | (S) A warning peculiar to VMS. Perl tried to read an element of %ENV |
| 2671 | from the CRTL's internal environment array and discovered the array was |
| 2672 | missing. You need to figure out where your CRTL misplaced its environ |
| 2673 | or define F<PERL_ENV_TABLES> (see L<perlvms>) so that environ is not searched. |
| 2674 | |
| 2675 | =item Can't remove %s: %s, skipping file |
| 2676 | |
| 2677 | (S) You requested an inplace edit without creating a backup file. Perl |
| 2678 | was unable to remove the original file to replace it with the modified |
| 2679 | file. The file was left unmodified. |
| 2680 | |
| 2681 | =item Can't return %s from lvalue subroutine |
| 2682 | |
| 2683 | (F) Perl detected an attempt to return illegal lvalues (such |
| 2684 | as temporary or readonly values) from a subroutine used as an lvalue. |
| 2685 | This is not allowed. |
| 2686 | |
| 2687 | =item Can't weaken a nonreference |
| 2688 | |
| 2689 | (F) You attempted to weaken something that was not a reference. Only |
| 2690 | references can be weakened. |
| 2691 | |
| 2692 | =item Character class [:%s:] unknown |
| 2693 | |
| 2694 | (F) The class in the character class [: :] syntax is unknown. |
| 2695 | See L<perlre>. |
| 2696 | |
| 2697 | =item Character class syntax [%s] belongs inside character classes |
| 2698 | |
| 2699 | (W unsafe) The character class constructs [: :], [= =], and [. .] go |
| 2700 | I<inside> character classes, the [] are part of the construct, |
| 2701 | for example: /[012[:alpha:]345]/. Note that [= =] and [. .] |
| 2702 | are not currently implemented; they are simply placeholders for |
| 2703 | future extensions. |
| 2704 | |
| 2705 | =item Constant is not %s reference |
| 2706 | |
| 2707 | (F) A constant value (perhaps declared using the C<use constant> pragma) |
| 2708 | is being dereferenced, but it amounts to the wrong type of reference. The |
| 2709 | message indicates the type of reference that was expected. This usually |
| 2710 | indicates a syntax error in dereferencing the constant value. |
| 2711 | See L<perlsub/"Constant Functions"> and L<constant>. |
| 2712 | |
| 2713 | =item constant(%s): %s |
| 2714 | |
| 2715 | (F) The parser found inconsistencies either while attempting to define an |
| 2716 | overloaded constant, or when trying to find the character name specified |
| 2717 | in the C<\N{...}> escape. Perhaps you forgot to load the corresponding |
| 2718 | C<overload> or C<charnames> pragma? See L<charnames> and L<overload>. |
| 2719 | |
| 2720 | =item CORE::%s is not a keyword |
| 2721 | |
| 2722 | (F) The CORE:: namespace is reserved for Perl keywords. |
| 2723 | |
| 2724 | =item defined(@array) is deprecated |
| 2725 | |
| 2726 | (D) defined() is not usually useful on arrays because it checks for an |
| 2727 | undefined I<scalar> value. If you want to see if the array is empty, |
| 2728 | just use C<if (@array) { # not empty }> for example. |
| 2729 | |
| 2730 | =item defined(%hash) is deprecated |
| 2731 | |
| 2732 | (D) defined() is not usually useful on hashes because it checks for an |
| 2733 | undefined I<scalar> value. If you want to see if the hash is empty, |
| 2734 | just use C<if (%hash) { # not empty }> for example. |
| 2735 | |
| 2736 | =item Did not produce a valid header |
| 2737 | |
| 2738 | See Server error. |
| 2739 | |
| 2740 | =item (Did you mean "local" instead of "our"?) |
| 2741 | |
| 2742 | (W misc) Remember that "our" does not localize the declared global variable. |
| 2743 | You have declared it again in the same lexical scope, which seems superfluous. |
| 2744 | |
| 2745 | =item Document contains no data |
| 2746 | |
| 2747 | See Server error. |
| 2748 | |
| 2749 | =item entering effective %s failed |
| 2750 | |
| 2751 | (F) While under the C<use filetest> pragma, switching the real and |
| 2752 | effective uids or gids failed. |
| 2753 | |
| 2754 | =item false [] range "%s" in regexp |
| 2755 | |
| 2756 | (W regexp) A character class range must start and end at a literal character, not |
| 2757 | another character class like C<\d> or C<[:alpha:]>. The "-" in your false |
| 2758 | range is interpreted as a literal "-". Consider quoting the "-", "\-". |
| 2759 | See L<perlre>. |
| 2760 | |
| 2761 | =item Filehandle %s opened only for output |
| 2762 | |
| 2763 | (W io) You tried to read from a filehandle opened only for writing. If you |
| 2764 | intended it to be a read/write filehandle, you needed to open it with |
| 2765 | "+<" or "+>" or "+>>" instead of with "<" or nothing. If |
| 2766 | you intended only to read from the file, use "<". See |
| 2767 | L<perlfunc/open>. |
| 2768 | |
| 2769 | =item flock() on closed filehandle %s |
| 2770 | |
| 2771 | (W closed) The filehandle you're attempting to flock() got itself closed some |
| 2772 | time before now. Check your logic flow. flock() operates on filehandles. |
| 2773 | Are you attempting to call flock() on a dirhandle by the same name? |
| 2774 | |
| 2775 | =item Global symbol "%s" requires explicit package name |
| 2776 | |
| 2777 | (F) You've said "use strict vars", which indicates that all variables |
| 2778 | must either be lexically scoped (using "my"), declared beforehand using |
| 2779 | "our", or explicitly qualified to say which package the global variable |
| 2780 | is in (using "::"). |
| 2781 | |
| 2782 | =item Hexadecimal number > 0xffffffff non-portable |
| 2783 | |
| 2784 | (W portable) The hexadecimal number you specified is larger than 2**32-1 |
| 2785 | (4294967295) and therefore non-portable between systems. See |
| 2786 | L<perlport> for more on portability concerns. |
| 2787 | |
| 2788 | =item Ill-formed CRTL environ value "%s" |
| 2789 | |
| 2790 | (W internal) A warning peculiar to VMS. Perl tried to read the CRTL's internal |
| 2791 | environ array, and encountered an element without the C<=> delimiter |
| 2792 | used to separate keys from values. The element is ignored. |
| 2793 | |
| 2794 | =item Ill-formed message in prime_env_iter: |%s| |
| 2795 | |
| 2796 | (W internal) A warning peculiar to VMS. Perl tried to read a logical name |
| 2797 | or CLI symbol definition when preparing to iterate over %ENV, and |
| 2798 | didn't see the expected delimiter between key and value, so the |
| 2799 | line was ignored. |
| 2800 | |
| 2801 | =item Illegal binary digit %s |
| 2802 | |
| 2803 | (F) You used a digit other than 0 or 1 in a binary number. |
| 2804 | |
| 2805 | =item Illegal binary digit %s ignored |
| 2806 | |
| 2807 | (W digit) You may have tried to use a digit other than 0 or 1 in a binary number. |
| 2808 | Interpretation of the binary number stopped before the offending digit. |
| 2809 | |
| 2810 | =item Illegal number of bits in vec |
| 2811 | |
| 2812 | (F) The number of bits in vec() (the third argument) must be a power of |
| 2813 | two from 1 to 32 (or 64, if your platform supports that). |
| 2814 | |
| 2815 | =item Integer overflow in %s number |
| 2816 | |
| 2817 | (W overflow) The hexadecimal, octal or binary number you have specified either |
| 2818 | as a literal or as an argument to hex() or oct() is too big for your |
| 2819 | architecture, and has been converted to a floating point number. On a |
| 2820 | 32-bit architecture the largest hexadecimal, octal or binary number |
| 2821 | representable without overflow is 0xFFFFFFFF, 037777777777, or |
| 2822 | 0b11111111111111111111111111111111 respectively. Note that Perl |
| 2823 | transparently promotes all numbers to a floating point representation |
| 2824 | internally--subject to loss of precision errors in subsequent |
| 2825 | operations. |
| 2826 | |
| 2827 | =item Invalid %s attribute: %s |
| 2828 | |
| 2829 | The indicated attribute for a subroutine or variable was not recognized |
| 2830 | by Perl or by a user-supplied handler. See L<attributes>. |
| 2831 | |
| 2832 | =item Invalid %s attributes: %s |
| 2833 | |
| 2834 | The indicated attributes for a subroutine or variable were not recognized |
| 2835 | by Perl or by a user-supplied handler. See L<attributes>. |
| 2836 | |
| 2837 | =item invalid [] range "%s" in regexp |
| 2838 | |
| 2839 | The offending range is now explicitly displayed. |
| 2840 | |
| 2841 | =item Invalid separator character %s in attribute list |
| 2842 | |
| 2843 | (F) Something other than a colon or whitespace was seen between the |
| 2844 | elements of an attribute list. If the previous attribute |
| 2845 | had a parenthesised parameter list, perhaps that list was terminated |
| 2846 | too soon. See L<attributes>. |
| 2847 | |
| 2848 | =item Invalid separator character %s in subroutine attribute list |
| 2849 | |
| 2850 | (F) Something other than a colon or whitespace was seen between the |
| 2851 | elements of a subroutine attribute list. If the previous attribute |
| 2852 | had a parenthesised parameter list, perhaps that list was terminated |
| 2853 | too soon. |
| 2854 | |
| 2855 | =item leaving effective %s failed |
| 2856 | |
| 2857 | (F) While under the C<use filetest> pragma, switching the real and |
| 2858 | effective uids or gids failed. |
| 2859 | |
| 2860 | =item Lvalue subs returning %s not implemented yet |
| 2861 | |
| 2862 | (F) Due to limitations in the current implementation, array and hash |
| 2863 | values cannot be returned in subroutines used in lvalue context. |
| 2864 | See L<perlsub/"Lvalue subroutines">. |
| 2865 | |
| 2866 | =item Method %s not permitted |
| 2867 | |
| 2868 | See Server error. |
| 2869 | |
| 2870 | =item Missing %sbrace%s on \N{} |
| 2871 | |
| 2872 | (F) Wrong syntax of character name literal C<\N{charname}> within |
| 2873 | double-quotish context. |
| 2874 | |
| 2875 | =item Missing command in piped open |
| 2876 | |
| 2877 | (W pipe) You used the C<open(FH, "| command")> or C<open(FH, "command |")> |
| 2878 | construction, but the command was missing or blank. |
| 2879 | |
| 2880 | =item Missing name in "my sub" |
| 2881 | |
| 2882 | (F) The reserved syntax for lexically scoped subroutines requires that they |
| 2883 | have a name with which they can be found. |
| 2884 | |
| 2885 | =item No %s specified for -%c |
| 2886 | |
| 2887 | (F) The indicated command line switch needs a mandatory argument, but |
| 2888 | you haven't specified one. |
| 2889 | |
| 2890 | =item No package name allowed for variable %s in "our" |
| 2891 | |
| 2892 | (F) Fully qualified variable names are not allowed in "our" declarations, |
| 2893 | because that doesn't make much sense under existing semantics. Such |
| 2894 | syntax is reserved for future extensions. |
| 2895 | |
| 2896 | =item No space allowed after -%c |
| 2897 | |
| 2898 | (F) The argument to the indicated command line switch must follow immediately |
| 2899 | after the switch, without intervening spaces. |
| 2900 | |
| 2901 | =item no UTC offset information; assuming local time is UTC |
| 2902 | |
| 2903 | (S) A warning peculiar to VMS. Perl was unable to find the local |
| 2904 | timezone offset, so it's assuming that local system time is equivalent |
| 2905 | to UTC. If it's not, define the logical name F<SYS$TIMEZONE_DIFFERENTIAL> |
| 2906 | to translate to the number of seconds which need to be added to UTC to |
| 2907 | get local time. |
| 2908 | |
| 2909 | =item Octal number > 037777777777 non-portable |
| 2910 | |
| 2911 | (W portable) The octal number you specified is larger than 2**32-1 (4294967295) |
| 2912 | and therefore non-portable between systems. See L<perlport> for more |
| 2913 | on portability concerns. |
| 2914 | |
| 2915 | See also L<perlport> for writing portable code. |
| 2916 | |
| 2917 | =item panic: del_backref |
| 2918 | |
| 2919 | (P) Failed an internal consistency check while trying to reset a weak |
| 2920 | reference. |
| 2921 | |
| 2922 | =item panic: kid popen errno read |
| 2923 | |
| 2924 | (F) forked child returned an incomprehensible message about its errno. |
| 2925 | |
| 2926 | =item panic: magic_killbackrefs |
| 2927 | |
| 2928 | (P) Failed an internal consistency check while trying to reset all weak |
| 2929 | references to an object. |
| 2930 | |
| 2931 | =item Parentheses missing around "%s" list |
| 2932 | |
| 2933 | (W parenthesis) You said something like |
| 2934 | |
| 2935 | my $foo, $bar = @_; |
| 2936 | |
| 2937 | when you meant |
| 2938 | |
| 2939 | my ($foo, $bar) = @_; |
| 2940 | |
| 2941 | Remember that "my", "our", and "local" bind tighter than comma. |
| 2942 | |
| 2943 | =item Possible unintended interpolation of %s in string |
| 2944 | |
| 2945 | (W ambiguous) It used to be that Perl would try to guess whether you |
| 2946 | wanted an array interpolated or a literal @. It no longer does this; |
| 2947 | arrays are now I<always> interpolated into strings. This means that |
| 2948 | if you try something like: |
| 2949 | |
| 2950 | print "fred@example.com"; |
| 2951 | |
| 2952 | and the array C<@example> doesn't exist, Perl is going to print |
| 2953 | C<fred.com>, which is probably not what you wanted. To get a literal |
| 2954 | C<@> sign in a string, put a backslash before it, just as you would |
| 2955 | to get a literal C<$> sign. |
| 2956 | |
| 2957 | =item Possible Y2K bug: %s |
| 2958 | |
| 2959 | (W y2k) You are concatenating the number 19 with another number, which |
| 2960 | could be a potential Year 2000 problem. |
| 2961 | |
| 2962 | =item pragma "attrs" is deprecated, use "sub NAME : ATTRS" instead |
| 2963 | |
| 2964 | (W deprecated) You have written something like this: |
| 2965 | |
| 2966 | sub doit |
| 2967 | { |
| 2968 | use attrs qw(locked); |
| 2969 | } |
| 2970 | |
| 2971 | You should use the new declaration syntax instead. |
| 2972 | |
| 2973 | sub doit : locked |
| 2974 | { |
| 2975 | ... |
| 2976 | |
| 2977 | The C<use attrs> pragma is now obsolete, and is only provided for |
| 2978 | backward-compatibility. See L<perlsub/"Subroutine Attributes">. |
| 2979 | |
| 2980 | |
| 2981 | =item Premature end of script headers |
| 2982 | |
| 2983 | See Server error. |
| 2984 | |
| 2985 | =item Repeat count in pack overflows |
| 2986 | |
| 2987 | (F) You can't specify a repeat count so large that it overflows |
| 2988 | your signed integers. See L<perlfunc/pack>. |
| 2989 | |
| 2990 | =item Repeat count in unpack overflows |
| 2991 | |
| 2992 | (F) You can't specify a repeat count so large that it overflows |
| 2993 | your signed integers. See L<perlfunc/unpack>. |
| 2994 | |
| 2995 | =item realloc() of freed memory ignored |
| 2996 | |
| 2997 | (S) An internal routine called realloc() on something that had already |
| 2998 | been freed. |
| 2999 | |
| 3000 | =item Reference is already weak |
| 3001 | |
| 3002 | (W misc) You have attempted to weaken a reference that is already weak. |
| 3003 | Doing so has no effect. |
| 3004 | |
| 3005 | =item setpgrp can't take arguments |
| 3006 | |
| 3007 | (F) Your system has the setpgrp() from BSD 4.2, which takes no arguments, |
| 3008 | unlike POSIX setpgid(), which takes a process ID and process group ID. |
| 3009 | |
| 3010 | =item Strange *+?{} on zero-length expression |
| 3011 | |
| 3012 | (W regexp) You applied a regular expression quantifier in a place where it |
| 3013 | makes no sense, such as on a zero-width assertion. |
| 3014 | Try putting the quantifier inside the assertion instead. For example, |
| 3015 | the way to match "abc" provided that it is followed by three |
| 3016 | repetitions of "xyz" is C</abc(?=(?:xyz){3})/>, not C</abc(?=xyz){3}/>. |
| 3017 | |
| 3018 | =item switching effective %s is not implemented |
| 3019 | |
| 3020 | (F) While under the C<use filetest> pragma, we cannot switch the |
| 3021 | real and effective uids or gids. |
| 3022 | |
| 3023 | =item This Perl can't reset CRTL environ elements (%s) |
| 3024 | |
| 3025 | =item This Perl can't set CRTL environ elements (%s=%s) |
| 3026 | |
| 3027 | (W internal) Warnings peculiar to VMS. You tried to change or delete an element |
| 3028 | of the CRTL's internal environ array, but your copy of Perl wasn't |
| 3029 | built with a CRTL that contained the setenv() function. You'll need to |
| 3030 | rebuild Perl with a CRTL that does, or redefine F<PERL_ENV_TABLES> (see |
| 3031 | L<perlvms>) so that the environ array isn't the target of the change to |
| 3032 | %ENV which produced the warning. |
| 3033 | |
| 3034 | =item Too late to run %s block |
| 3035 | |
| 3036 | (W void) A CHECK or INIT block is being defined during run time proper, |
| 3037 | when the opportunity to run them has already passed. Perhaps you are |
| 3038 | loading a file with C<require> or C<do> when you should be using |
| 3039 | C<use> instead. Or perhaps you should put the C<require> or C<do> |
| 3040 | inside a BEGIN block. |
| 3041 | |
| 3042 | =item Unknown open() mode '%s' |
| 3043 | |
| 3044 | (F) The second argument of 3-argument open() is not among the list |
| 3045 | of valid modes: C<< < >>, C<< > >>, C<<< >> >>>, C<< +< >>, |
| 3046 | C<< +> >>, C<<< +>> >>>, C<-|>, C<|->. |
| 3047 | |
| 3048 | =item Unknown process %x sent message to prime_env_iter: %s |
| 3049 | |
| 3050 | (P) An error peculiar to VMS. Perl was reading values for %ENV before |
| 3051 | iterating over it, and someone else stuck a message in the stream of |
| 3052 | data Perl expected. Someone's very confused, or perhaps trying to |
| 3053 | subvert Perl's population of %ENV for nefarious purposes. |
| 3054 | |
| 3055 | =item Unrecognized escape \\%c passed through |
| 3056 | |
| 3057 | (W misc) You used a backslash-character combination which is not recognized |
| 3058 | by Perl. The character was understood literally. |
| 3059 | |
| 3060 | =item Unterminated attribute parameter in attribute list |
| 3061 | |
| 3062 | (F) The lexer saw an opening (left) parenthesis character while parsing an |
| 3063 | attribute list, but the matching closing (right) parenthesis |
| 3064 | character was not found. You may need to add (or remove) a backslash |
| 3065 | character to get your parentheses to balance. See L<attributes>. |
| 3066 | |
| 3067 | =item Unterminated attribute list |
| 3068 | |
| 3069 | (F) The lexer found something other than a simple identifier at the start |
| 3070 | of an attribute, and it wasn't a semicolon or the start of a |
| 3071 | block. Perhaps you terminated the parameter list of the previous attribute |
| 3072 | too soon. See L<attributes>. |
| 3073 | |
| 3074 | =item Unterminated attribute parameter in subroutine attribute list |
| 3075 | |
| 3076 | (F) The lexer saw an opening (left) parenthesis character while parsing a |
| 3077 | subroutine attribute list, but the matching closing (right) parenthesis |
| 3078 | character was not found. You may need to add (or remove) a backslash |
| 3079 | character to get your parentheses to balance. |
| 3080 | |
| 3081 | =item Unterminated subroutine attribute list |
| 3082 | |
| 3083 | (F) The lexer found something other than a simple identifier at the start |
| 3084 | of a subroutine attribute, and it wasn't a semicolon or the start of a |
| 3085 | block. Perhaps you terminated the parameter list of the previous attribute |
| 3086 | too soon. |
| 3087 | |
| 3088 | =item Value of CLI symbol "%s" too long |
| 3089 | |
| 3090 | (W misc) A warning peculiar to VMS. Perl tried to read the value of an %ENV |
| 3091 | element from a CLI symbol table, and found a resultant string longer |
| 3092 | than 1024 characters. The return value has been truncated to 1024 |
| 3093 | characters. |
| 3094 | |
| 3095 | =item Version number must be a constant number |
| 3096 | |
| 3097 | (P) The attempt to translate a C<use Module n.n LIST> statement into |
| 3098 | its equivalent C<BEGIN> block found an internal inconsistency with |
| 3099 | the version number. |
| 3100 | |
| 3101 | =back |
| 3102 | |
| 3103 | =head1 New tests |
| 3104 | |
| 3105 | =over 4 |
| 3106 | |
| 3107 | =item lib/attrs |
| 3108 | |
| 3109 | Compatibility tests for C<sub : attrs> vs the older C<use attrs>. |
| 3110 | |
| 3111 | =item lib/env |
| 3112 | |
| 3113 | Tests for new environment scalar capability (e.g., C<use Env qw($BAR);>). |
| 3114 | |
| 3115 | =item lib/env-array |
| 3116 | |
| 3117 | Tests for new environment array capability (e.g., C<use Env qw(@PATH);>). |
| 3118 | |
| 3119 | =item lib/io_const |
| 3120 | |
| 3121 | IO constants (SEEK_*, _IO*). |
| 3122 | |
| 3123 | =item lib/io_dir |
| 3124 | |
| 3125 | Directory-related IO methods (new, read, close, rewind, tied delete). |
| 3126 | |
| 3127 | =item lib/io_multihomed |
| 3128 | |
| 3129 | INET sockets with multi-homed hosts. |
| 3130 | |
| 3131 | =item lib/io_poll |
| 3132 | |
| 3133 | IO poll(). |
| 3134 | |
| 3135 | =item lib/io_unix |
| 3136 | |
| 3137 | UNIX sockets. |
| 3138 | |
| 3139 | =item op/attrs |
| 3140 | |
| 3141 | Regression tests for C<my ($x,@y,%z) : attrs> and <sub : attrs>. |
| 3142 | |
| 3143 | =item op/filetest |
| 3144 | |
| 3145 | File test operators. |
| 3146 | |
| 3147 | =item op/lex_assign |
| 3148 | |
| 3149 | Verify operations that access pad objects (lexicals and temporaries). |
| 3150 | |
| 3151 | =item op/exists_sub |
| 3152 | |
| 3153 | Verify C<exists &sub> operations. |
| 3154 | |
| 3155 | =back |
| 3156 | |
| 3157 | =head1 Incompatible Changes |
| 3158 | |
| 3159 | =head2 Perl Source Incompatibilities |
| 3160 | |
| 3161 | Beware that any new warnings that have been added or old ones |
| 3162 | that have been enhanced are B<not> considered incompatible changes. |
| 3163 | |
| 3164 | Since all new warnings must be explicitly requested via the C<-w> |
| 3165 | switch or the C<warnings> pragma, it is ultimately the programmer's |
| 3166 | responsibility to ensure that warnings are enabled judiciously. |
| 3167 | |
| 3168 | =over 4 |
| 3169 | |
| 3170 | =item CHECK is a new keyword |
| 3171 | |
| 3172 | All subroutine definitions named CHECK are now special. See |
| 3173 | C</"Support for CHECK blocks"> for more information. |
| 3174 | |
| 3175 | =item Treatment of list slices of undef has changed |
| 3176 | |
| 3177 | There is a potential incompatibility in the behavior of list slices |
| 3178 | that are comprised entirely of undefined values. |
| 3179 | See L</"Behavior of list slices is more consistent">. |
| 3180 | |
| 3181 | =item Format of $English::PERL_VERSION is different |
| 3182 | |
| 3183 | The English module now sets $PERL_VERSION to $^V (a string value) rather |
| 3184 | than C<$]> (a numeric value). This is a potential incompatibility. |
| 3185 | Send us a report via perlbug if you are affected by this. |
| 3186 | |
| 3187 | See L</"Improved Perl version numbering system"> for the reasons for |
| 3188 | this change. |
| 3189 | |
| 3190 | =item Literals of the form C<1.2.3> parse differently |
| 3191 | |
| 3192 | Previously, numeric literals with more than one dot in them were |
| 3193 | interpreted as a floating point number concatenated with one or more |
| 3194 | numbers. Such "numbers" are now parsed as strings composed of the |
| 3195 | specified ordinals. |
| 3196 | |
| 3197 | For example, C<print 97.98.99> used to output C<97.9899> in earlier |
| 3198 | versions, but now prints C<abc>. |
| 3199 | |
| 3200 | See L</"Support for strings represented as a vector of ordinals">. |
| 3201 | |
| 3202 | =item Possibly changed pseudo-random number generator |
| 3203 | |
| 3204 | Perl programs that depend on reproducing a specific set of pseudo-random |
| 3205 | numbers may now produce different output due to improvements made to the |
| 3206 | rand() builtin. You can use C<sh Configure -Drandfunc=rand> to obtain |
| 3207 | the old behavior. |
| 3208 | |
| 3209 | See L</"Better pseudo-random number generator">. |
| 3210 | |
| 3211 | =item Hashing function for hash keys has changed |
| 3212 | |
| 3213 | Even though Perl hashes are not order preserving, the apparently |
| 3214 | random order encountered when iterating on the contents of a hash |
| 3215 | is actually determined by the hashing algorithm used. Improvements |
| 3216 | in the algorithm may yield a random order that is B<different> from |
| 3217 | that of previous versions, especially when iterating on hashes. |
| 3218 | |
| 3219 | See L</"Better worst-case behavior of hashes"> for additional |
| 3220 | information. |
| 3221 | |
| 3222 | =item C<undef> fails on read only values |
| 3223 | |
| 3224 | Using the C<undef> operator on a readonly value (such as $1) has |
| 3225 | the same effect as assigning C<undef> to the readonly value--it |
| 3226 | throws an exception. |
| 3227 | |
| 3228 | =item Close-on-exec bit may be set on pipe and socket handles |
| 3229 | |
| 3230 | Pipe and socket handles are also now subject to the close-on-exec |
| 3231 | behavior determined by the special variable $^F. |
| 3232 | |
| 3233 | See L</"More consistent close-on-exec behavior">. |
| 3234 | |
| 3235 | =item Writing C<"$$1"> to mean C<"${$}1"> is unsupported |
| 3236 | |
| 3237 | Perl 5.004 deprecated the interpretation of C<$$1> and |
| 3238 | similar within interpolated strings to mean C<$$ . "1">, |
| 3239 | but still allowed it. |
| 3240 | |
| 3241 | In Perl 5.6.0 and later, C<"$$1"> always means C<"${$1}">. |
| 3242 | |
| 3243 | =item delete(), each(), values() and C<\(%h)> |
| 3244 | |
| 3245 | operate on aliases to values, not copies |
| 3246 | |
| 3247 | delete(), each(), values() and hashes (e.g. C<\(%h)>) |
| 3248 | in a list context return the actual |
| 3249 | values in the hash, instead of copies (as they used to in earlier |
| 3250 | versions). Typical idioms for using these constructs copy the |
| 3251 | returned values, but this can make a significant difference when |
| 3252 | creating references to the returned values. Keys in the hash are still |
| 3253 | returned as copies when iterating on a hash. |
| 3254 | |
| 3255 | See also L</"delete(), each(), values() and hash iteration are faster">. |
| 3256 | |
| 3257 | =item vec(EXPR,OFFSET,BITS) enforces powers-of-two BITS |
| 3258 | |
| 3259 | vec() generates a run-time error if the BITS argument is not |
| 3260 | a valid power-of-two integer. |
| 3261 | |
| 3262 | =item Text of some diagnostic output has changed |
| 3263 | |
| 3264 | Most references to internal Perl operations in diagnostics |
| 3265 | have been changed to be more descriptive. This may be an |
| 3266 | issue for programs that may incorrectly rely on the exact |
| 3267 | text of diagnostics for proper functioning. |
| 3268 | |
| 3269 | =item C<%@> has been removed |
| 3270 | |
| 3271 | The undocumented special variable C<%@> that used to accumulate |
| 3272 | "background" errors (such as those that happen in DESTROY()) |
| 3273 | has been removed, because it could potentially result in memory |
| 3274 | leaks. |
| 3275 | |
| 3276 | =item Parenthesized not() behaves like a list operator |
| 3277 | |
| 3278 | The C<not> operator now falls under the "if it looks like a function, |
| 3279 | it behaves like a function" rule. |
| 3280 | |
| 3281 | As a result, the parenthesized form can be used with C<grep> and C<map>. |
| 3282 | The following construct used to be a syntax error before, but it works |
| 3283 | as expected now: |
| 3284 | |
| 3285 | grep not($_), @things; |
| 3286 | |
| 3287 | On the other hand, using C<not> with a literal list slice may not |
| 3288 | work. The following previously allowed construct: |
| 3289 | |
| 3290 | print not (1,2,3)[0]; |
| 3291 | |
| 3292 | needs to be written with additional parentheses now: |
| 3293 | |
| 3294 | print not((1,2,3)[0]); |
| 3295 | |
| 3296 | The behavior remains unaffected when C<not> is not followed by parentheses. |
| 3297 | |
| 3298 | =item Semantics of bareword prototype C<(*)> have changed |
| 3299 | |
| 3300 | The semantics of the bareword prototype C<*> have changed. Perl 5.005 |
| 3301 | always coerced simple scalar arguments to a typeglob, which wasn't useful |
| 3302 | in situations where the subroutine must distinguish between a simple |
| 3303 | scalar and a typeglob. The new behavior is to not coerce bareword |
| 3304 | arguments to a typeglob. The value will always be visible as either |
| 3305 | a simple scalar or as a reference to a typeglob. |
| 3306 | |
| 3307 | See L</"More functional bareword prototype (*)">. |
| 3308 | |
| 3309 | =item Semantics of bit operators may have changed on 64-bit platforms |
| 3310 | |
| 3311 | If your platform is either natively 64-bit or if Perl has been |
| 3312 | configured to used 64-bit integers, i.e., $Config{ivsize} is 8, |
| 3313 | there may be a potential incompatibility in the behavior of bitwise |
| 3314 | numeric operators (& | ^ ~ << >>). These operators used to strictly |
| 3315 | operate on the lower 32 bits of integers in previous versions, but now |
| 3316 | operate over the entire native integral width. In particular, note |
| 3317 | that unary C<~> will produce different results on platforms that have |
| 3318 | different $Config{ivsize}. For portability, be sure to mask off |
| 3319 | the excess bits in the result of unary C<~>, e.g., C<~$x & 0xffffffff>. |
| 3320 | |
| 3321 | See L</"Bit operators support full native integer width">. |
| 3322 | |
| 3323 | =item More builtins taint their results |
| 3324 | |
| 3325 | As described in L</"Improved security features">, there may be more |
| 3326 | sources of taint in a Perl program. |
| 3327 | |
| 3328 | To avoid these new tainting behaviors, you can build Perl with the |
| 3329 | Configure option C<-Accflags=-DINCOMPLETE_TAINTS>. Beware that the |
| 3330 | ensuing perl binary may be insecure. |
| 3331 | |
| 3332 | =back |
| 3333 | |
| 3334 | =head2 C Source Incompatibilities |
| 3335 | |
| 3336 | =over 4 |
| 3337 | |
| 3338 | =item C<PERL_POLLUTE> |
| 3339 | |
| 3340 | Release 5.005 grandfathered old global symbol names by providing preprocessor |
| 3341 | macros for extension source compatibility. As of release 5.6.0, these |
| 3342 | preprocessor definitions are not available by default. You need to explicitly |
| 3343 | compile perl with C<-DPERL_POLLUTE> to get these definitions. For |
| 3344 | extensions still using the old symbols, this option can be |
| 3345 | specified via MakeMaker: |
| 3346 | |
| 3347 | perl Makefile.PL POLLUTE=1 |
| 3348 | |
| 3349 | =item C<PERL_IMPLICIT_CONTEXT> |
| 3350 | |
| 3351 | This new build option provides a set of macros for all API functions |
| 3352 | such that an implicit interpreter/thread context argument is passed to |
| 3353 | every API function. As a result of this, something like C<sv_setsv(foo,bar)> |
| 3354 | amounts to a macro invocation that actually translates to something like |
| 3355 | C<Perl_sv_setsv(my_perl,foo,bar)>. While this is generally expected |
| 3356 | to not have any significant source compatibility issues, the difference |
| 3357 | between a macro and a real function call will need to be considered. |
| 3358 | |
| 3359 | This means that there B<is> a source compatibility issue as a result of |
| 3360 | this if your extensions attempt to use pointers to any of the Perl API |
| 3361 | functions. |
| 3362 | |
| 3363 | Note that the above issue is not relevant to the default build of |
| 3364 | Perl, whose interfaces continue to match those of prior versions |
| 3365 | (but subject to the other options described here). |
| 3366 | |
| 3367 | See L<perlguts/"The Perl API"> for detailed information on the |
| 3368 | ramifications of building Perl with this option. |
| 3369 | |
| 3370 | NOTE: PERL_IMPLICIT_CONTEXT is automatically enabled whenever Perl is built |
| 3371 | with one of -Dusethreads, -Dusemultiplicity, or both. It is not |
| 3372 | intended to be enabled by users at this time. |
| 3373 | |
| 3374 | =item C<PERL_POLLUTE_MALLOC> |
| 3375 | |
| 3376 | Enabling Perl's malloc in release 5.005 and earlier caused the namespace of |
| 3377 | the system's malloc family of functions to be usurped by the Perl versions, |
| 3378 | since by default they used the same names. Besides causing problems on |
| 3379 | platforms that do not allow these functions to be cleanly replaced, this |
| 3380 | also meant that the system versions could not be called in programs that |
| 3381 | used Perl's malloc. Previous versions of Perl have allowed this behaviour |
| 3382 | to be suppressed with the HIDEMYMALLOC and EMBEDMYMALLOC preprocessor |
| 3383 | definitions. |
| 3384 | |
| 3385 | As of release 5.6.0, Perl's malloc family of functions have default names |
| 3386 | distinct from the system versions. You need to explicitly compile perl with |
| 3387 | C<-DPERL_POLLUTE_MALLOC> to get the older behaviour. HIDEMYMALLOC |
| 3388 | and EMBEDMYMALLOC have no effect, since the behaviour they enabled is now |
| 3389 | the default. |
| 3390 | |
| 3391 | Note that these functions do B<not> constitute Perl's memory allocation API. |
| 3392 | See L<perlguts/"Memory Allocation"> for further information about that. |
| 3393 | |
| 3394 | =back |
| 3395 | |
| 3396 | =head2 Compatible C Source API Changes |
| 3397 | |
| 3398 | =over 4 |
| 3399 | |
| 3400 | =item C<PATCHLEVEL> is now C<PERL_VERSION> |
| 3401 | |
| 3402 | The cpp macros C<PERL_REVISION>, C<PERL_VERSION>, and C<PERL_SUBVERSION> |
| 3403 | are now available by default from perl.h, and reflect the base revision, |
| 3404 | patchlevel, and subversion respectively. C<PERL_REVISION> had no |
| 3405 | prior equivalent, while C<PERL_VERSION> and C<PERL_SUBVERSION> were |
| 3406 | previously available as C<PATCHLEVEL> and C<SUBVERSION>. |
| 3407 | |
| 3408 | The new names cause less pollution of the B<cpp> namespace and reflect what |
| 3409 | the numbers have come to stand for in common practice. For compatibility, |
| 3410 | the old names are still supported when F<patchlevel.h> is explicitly |
| 3411 | included (as required before), so there is no source incompatibility |
| 3412 | from the change. |
| 3413 | |
| 3414 | =back |
| 3415 | |
| 3416 | =head2 Binary Incompatibilities |
| 3417 | |
| 3418 | In general, the default build of this release is expected to be binary |
| 3419 | compatible for extensions built with the 5.005 release or its maintenance |
| 3420 | versions. However, specific platforms may have broken binary compatibility |
| 3421 | due to changes in the defaults used in hints files. Therefore, please be |
| 3422 | sure to always check the platform-specific README files for any notes to |
| 3423 | the contrary. |
| 3424 | |
| 3425 | The usethreads or usemultiplicity builds are B<not> binary compatible |
| 3426 | with the corresponding builds in 5.005. |
| 3427 | |
| 3428 | On platforms that require an explicit list of exports (AIX, OS/2 and Windows, |
| 3429 | among others), purely internal symbols such as parser functions and the |
| 3430 | run time opcodes are not exported by default. Perl 5.005 used to export |
| 3431 | all functions irrespective of whether they were considered part of the |
| 3432 | public API or not. |
| 3433 | |
| 3434 | For the full list of public API functions, see L<perlapi>. |
| 3435 | |
| 3436 | =head1 Known Problems |
| 3437 | |
| 3438 | =head2 Localizing a tied hash element may leak memory |
| 3439 | |
| 3440 | As of the 5.6.1 release, there is a known leak when code such as this |
| 3441 | is executed: |
| 3442 | |
| 3443 | use Tie::Hash; |
| 3444 | tie my %tie_hash => 'Tie::StdHash'; |
| 3445 | |
| 3446 | ... |
| 3447 | |
| 3448 | local($tie_hash{Foo}) = 1; # leaks |
| 3449 | |
| 3450 | =head2 Known test failures |
| 3451 | |
| 3452 | =over |
| 3453 | |
| 3454 | =item * |
| 3455 | |
| 3456 | 64-bit builds |
| 3457 | |
| 3458 | Subtest #15 of lib/b.t may fail under 64-bit builds on platforms such |
| 3459 | as HP-UX PA64 and Linux IA64. The issue is still being investigated. |
| 3460 | |
| 3461 | The lib/io_multihomed test may hang in HP-UX if Perl has been |
| 3462 | configured to be 64-bit. Because other 64-bit platforms do not |
| 3463 | hang in this test, HP-UX is suspect. All other tests pass |
| 3464 | in 64-bit HP-UX. The test attempts to create and connect to |
| 3465 | "multihomed" sockets (sockets which have multiple IP addresses). |
| 3466 | |
| 3467 | Note that 64-bit support is still experimental. |
| 3468 | |
| 3469 | =item * |
| 3470 | |
| 3471 | Failure of Thread tests |
| 3472 | |
| 3473 | The subtests 19 and 20 of lib/thr5005.t test are known to fail due to |
| 3474 | fundamental problems in the 5.005 threading implementation. These are |
| 3475 | not new failures--Perl 5.005_0x has the same bugs, but didn't have these |
| 3476 | tests. (Note that support for 5.005-style threading remains experimental.) |
| 3477 | |
| 3478 | =item * |
| 3479 | |
| 3480 | NEXTSTEP 3.3 POSIX test failure |
| 3481 | |
| 3482 | In NEXTSTEP 3.3p2 the implementation of the strftime(3) in the |
| 3483 | operating system libraries is buggy: the %j format numbers the days of |
| 3484 | a month starting from zero, which, while being logical to programmers, |
| 3485 | will cause the subtests 19 to 27 of the lib/posix test may fail. |
| 3486 | |
| 3487 | =item * |
| 3488 | |
| 3489 | Tru64 (aka Digital UNIX, aka DEC OSF/1) lib/sdbm test failure with gcc |
| 3490 | |
| 3491 | If compiled with gcc 2.95 the lib/sdbm test will fail (dump core). |
| 3492 | The cure is to use the vendor cc, it comes with the operating system |
| 3493 | and produces good code. |
| 3494 | |
| 3495 | =back |
| 3496 | |
| 3497 | =head2 EBCDIC platforms not fully supported |
| 3498 | |
| 3499 | In earlier releases of Perl, EBCDIC environments like OS390 (also |
| 3500 | known as Open Edition MVS) and VM-ESA were supported. Due to changes |
| 3501 | required by the UTF-8 (Unicode) support, the EBCDIC platforms are not |
| 3502 | supported in Perl 5.6.0. |
| 3503 | |
| 3504 | The 5.6.1 release improves support for EBCDIC platforms, but they |
| 3505 | are not fully supported yet. |
| 3506 | |
| 3507 | =head2 UNICOS/mk CC failures during Configure run |
| 3508 | |
| 3509 | In UNICOS/mk the following errors may appear during the Configure run: |
| 3510 | |
| 3511 | Guessing which symbols your C compiler and preprocessor define... |
| 3512 | CC-20 cc: ERROR File = try.c, Line = 3 |
| 3513 | ... |
| 3514 | bad switch yylook 79bad switch yylook 79bad switch yylook 79bad switch yylook 79#ifdef A29K |
| 3515 | ... |
| 3516 | 4 errors detected in the compilation of "try.c". |
| 3517 | |
| 3518 | The culprit is the broken awk of UNICOS/mk. The effect is fortunately |
| 3519 | rather mild: Perl itself is not adversely affected by the error, only |
| 3520 | the h2ph utility coming with Perl, and that is rather rarely needed |
| 3521 | these days. |
| 3522 | |
| 3523 | =head2 Arrow operator and arrays |
| 3524 | |
| 3525 | When the left argument to the arrow operator C<< -> >> is an array, or |
| 3526 | the C<scalar> operator operating on an array, the result of the |
| 3527 | operation must be considered erroneous. For example: |
| 3528 | |
| 3529 | @x->[2] |
| 3530 | scalar(@x)->[2] |
| 3531 | |
| 3532 | These expressions will get run-time errors in some future release of |
| 3533 | Perl. |
| 3534 | |
| 3535 | =head2 Experimental features |
| 3536 | |
| 3537 | As discussed above, many features are still experimental. Interfaces and |
| 3538 | implementation of these features are subject to change, and in extreme cases, |
| 3539 | even subject to removal in some future release of Perl. These features |
| 3540 | include the following: |
| 3541 | |
| 3542 | =over 4 |
| 3543 | |
| 3544 | =item Threads |
| 3545 | |
| 3546 | =item Unicode |
| 3547 | |
| 3548 | =item 64-bit support |
| 3549 | |
| 3550 | =item Lvalue subroutines |
| 3551 | |
| 3552 | =item Weak references |
| 3553 | |
| 3554 | =item The pseudo-hash data type |
| 3555 | |
| 3556 | =item The Compiler suite |
| 3557 | |
| 3558 | =item Internal implementation of file globbing |
| 3559 | |
| 3560 | =item The DB module |
| 3561 | |
| 3562 | =item The regular expression code constructs: |
| 3563 | |
| 3564 | C<(?{ code })> and C<(??{ code })> |
| 3565 | |
| 3566 | =back |
| 3567 | |
| 3568 | =head1 Obsolete Diagnostics |
| 3569 | |
| 3570 | =over 4 |
| 3571 | |
| 3572 | =item Character class syntax [: :] is reserved for future extensions |
| 3573 | |
| 3574 | (W) Within regular expression character classes ([]) the syntax beginning |
| 3575 | with "[:" and ending with ":]" is reserved for future extensions. |
| 3576 | If you need to represent those character sequences inside a regular |
| 3577 | expression character class, just quote the square brackets with the |
| 3578 | backslash: "\[:" and ":\]". |
| 3579 | |
| 3580 | =item Ill-formed logical name |%s| in prime_env_iter |
| 3581 | |
| 3582 | (W) A warning peculiar to VMS. A logical name was encountered when preparing |
| 3583 | to iterate over %ENV which violates the syntactic rules governing logical |
| 3584 | names. Because it cannot be translated normally, it is skipped, and will not |
| 3585 | appear in %ENV. This may be a benign occurrence, as some software packages |
| 3586 | might directly modify logical name tables and introduce nonstandard names, |
| 3587 | or it may indicate that a logical name table has been corrupted. |
| 3588 | |
| 3589 | =item In string, @%s now must be written as \@%s |
| 3590 | |
| 3591 | The description of this error used to say: |
| 3592 | |
| 3593 | (Someday it will simply assume that an unbackslashed @ |
| 3594 | interpolates an array.) |
| 3595 | |
| 3596 | That day has come, and this fatal error has been removed. It has been |
| 3597 | replaced by a non-fatal warning instead. |
| 3598 | See L</Arrays now always interpolate into double-quoted strings> for |
| 3599 | details. |
| 3600 | |
| 3601 | =item Probable precedence problem on %s |
| 3602 | |
| 3603 | (W) The compiler found a bareword where it expected a conditional, |
| 3604 | which often indicates that an || or && was parsed as part of the |
| 3605 | last argument of the previous construct, for example: |
| 3606 | |
| 3607 | open FOO || die; |
| 3608 | |
| 3609 | =item regexp too big |
| 3610 | |
| 3611 | (F) The current implementation of regular expressions uses shorts as |
| 3612 | address offsets within a string. Unfortunately this means that if |
| 3613 | the regular expression compiles to longer than 32767, it'll blow up. |
| 3614 | Usually when you want a regular expression this big, there is a better |
| 3615 | way to do it with multiple statements. See L<perlre>. |
| 3616 | |
| 3617 | =item Use of "$$<digit>" to mean "${$}<digit>" is deprecated |
| 3618 | |
| 3619 | (D) Perl versions before 5.004 misinterpreted any type marker followed |
| 3620 | by "$" and a digit. For example, "$$0" was incorrectly taken to mean |
| 3621 | "${$}0" instead of "${$0}". This bug is (mostly) fixed in Perl 5.004. |
| 3622 | |
| 3623 | However, the developers of Perl 5.004 could not fix this bug completely, |
| 3624 | because at least two widely-used modules depend on the old meaning of |
| 3625 | "$$0" in a string. So Perl 5.004 still interprets "$$<digit>" in the |
| 3626 | old (broken) way inside strings; but it generates this message as a |
| 3627 | warning. And in Perl 5.005, this special treatment will cease. |
| 3628 | |
| 3629 | =back |
| 3630 | |
| 3631 | =head1 Reporting Bugs |
| 3632 | |
| 3633 | If you find what you think is a bug, you might check the |
| 3634 | articles recently posted to the comp.lang.perl.misc newsgroup. |
| 3635 | There may also be information at http://www.perl.com/ , the Perl |
| 3636 | Home Page. |
| 3637 | |
| 3638 | If you believe you have an unreported bug, please run the B<perlbug> |
| 3639 | program included with your release. Be sure to trim your bug down |
| 3640 | to a tiny but sufficient test case. Your bug report, along with the |
| 3641 | output of C<perl -V>, will be sent off to perlbug@perl.org to be |
| 3642 | analysed by the Perl porting team. |
| 3643 | |
| 3644 | =head1 SEE ALSO |
| 3645 | |
| 3646 | The F<Changes> file for exhaustive details on what changed. |
| 3647 | |
| 3648 | The F<INSTALL> file for how to build Perl. |
| 3649 | |
| 3650 | The F<README> file for general stuff. |
| 3651 | |
| 3652 | The F<Artistic> and F<Copying> files for copyright information. |
| 3653 | |
| 3654 | =head1 HISTORY |
| 3655 | |
| 3656 | Written by Gurusamy Sarathy <F<gsar@ActiveState.com>>, with many |
| 3657 | contributions from The Perl Porters. |
| 3658 | |
| 3659 | Send omissions or corrections to <F<perlbug@perl.org>>. |
| 3660 | |
| 3661 | =cut |