| 1 | =encoding utf8 |
| 2 | |
| 3 | =head1 NAME |
| 4 | |
| 5 | perl5170delta - what is new for perl v5.17.0 |
| 6 | |
| 7 | =head1 DESCRIPTION |
| 8 | |
| 9 | This document describes differences between the 5.16.0 release and |
| 10 | the 5.17.0 release. |
| 11 | |
| 12 | If you are upgrading from an earlier release such as 5.16.0, first read |
| 13 | L<perl5160delta>, which describes differences between 5.14.0 and |
| 14 | 5.16.0. |
| 15 | |
| 16 | =head1 Incompatible Changes |
| 17 | |
| 18 | =head2 qw(...) can no longer be used as parentheses |
| 19 | |
| 20 | C<qw> lists used to fool the parser into thinking they were always |
| 21 | surrounded by parentheses. This permitted some surprising constructions |
| 22 | such as C<foreach $x qw(a b c) {...}>, which should really be written |
| 23 | C<foreach $x (qw(a b c)) {...}>. These would sometimes get the lexer into |
| 24 | the wrong state, so they didn't fully work, and the similar C<foreach qw(a |
| 25 | b c) {...}> that one might expect to be permitted never worked at all. |
| 26 | |
| 27 | This side effect of C<qw> has now been abolished. It has been deprecated |
| 28 | since Perl 5.13.11. It is now necessary to use real parentheses |
| 29 | everywhere that the grammar calls for them. |
| 30 | |
| 31 | =head2 C<\s> in regular expressions now matches a Vertical Tab (experimental) |
| 32 | |
| 33 | This is an experiment early in the development cycle to see what |
| 34 | repercussions arise from this change. It may well be that we decide |
| 35 | to require a C<"use feature"> to activate this behavior. Because |
| 36 | of the experimental nature of this, which may be reversed, the |
| 37 | documentation has not been changed to reflect it. |
| 38 | |
| 39 | =head1 Deprecations |
| 40 | |
| 41 | =head2 Unescaped braces in regexps |
| 42 | |
| 43 | Literal unescaped C<{> in regular expressions is now deprecated. Every |
| 44 | brace character should be either escaped (by a preceding backslash) or |
| 45 | part of a construct where it's a metacharacter. This catches likely typos |
| 46 | such as C</f{,3}/>. It will also allow braces to be used in the future |
| 47 | to delimit parameters to metacharacters that currently take no parameters. |
| 48 | |
| 49 | =head1 Performance Enhancements |
| 50 | |
| 51 | =over 4 |
| 52 | |
| 53 | =item * |
| 54 | |
| 55 | Filetest ops manage the stack in a fractionally more efficient manner. |
| 56 | |
| 57 | =item * |
| 58 | |
| 59 | Globs used in a numeric context are now numerified directly in most cases, |
| 60 | rather than being numerified via stringification. |
| 61 | |
| 62 | =back |
| 63 | |
| 64 | =head1 Modules and Pragmata |
| 65 | |
| 66 | =head2 Updated Modules and Pragmata |
| 67 | |
| 68 | =over 4 |
| 69 | |
| 70 | =item * |
| 71 | |
| 72 | L<B> has been upgraded from version 1.34 to 1.35. |
| 73 | |
| 74 | The C<stashlen> method of COPs has been added. This provides access to an |
| 75 | internal field added in perl 5.16 under threaded builds [perl #113034]. |
| 76 | |
| 77 | =item * |
| 78 | |
| 79 | L<ExtUtils::ParseXS> has been upgraded from version 3.16 to 3.17. |
| 80 | |
| 81 | The generated C code now avoids unnecessarily incrementing |
| 82 | C<PL_amagic_generation> on Perl versions where it's done automatically |
| 83 | (or on current Perl where the variable no longer exists). |
| 84 | |
| 85 | =item * |
| 86 | |
| 87 | L<File::DosGlob> has been upgraded from version 1.06 to 1.07. |
| 88 | |
| 89 | Small documentation and comment fixes. |
| 90 | |
| 91 | =item * |
| 92 | |
| 93 | L<File::Find> has been upgraded from version 1.20 to 1.21. |
| 94 | |
| 95 | Individual files may now appear in list of directories to be searched |
| 96 | [perl #59750]. |
| 97 | |
| 98 | =item * |
| 99 | |
| 100 | L<File::stat> has been upgraded from version 1.05 to 1.06. |
| 101 | |
| 102 | C<File::stat> ignores the L<filetest> pragma, and warns when used in |
| 103 | combination therewith. But it was not warning for C<-r>. This has been |
| 104 | fixed [perl #111640]. |
| 105 | |
| 106 | C<-p> now works, and does not return false for pipes [perl #111638]. |
| 107 | |
| 108 | =item * |
| 109 | |
| 110 | L<Hash::Util> has been upgraded from version 0.11 to 0.12. |
| 111 | |
| 112 | C<hash_unlocked> and C<hashref_unlocked> now returns true if the hash is |
| 113 | unlocked, instead of always returning false [perl #112126]. |
| 114 | |
| 115 | C<hash_unlocked>, C<hashref_unlocked>, C<lock_hash_recurse> and |
| 116 | C<unlock_hash_recurse> are now exportable [perl #112126]. |
| 117 | |
| 118 | Two new functions, C<hash_locked> and C<hashref_locked>, have been added. |
| 119 | Oddly enough, these two functions were already exported, even though they |
| 120 | did not exist [perl #112126]. |
| 121 | |
| 122 | =item * |
| 123 | |
| 124 | L<Module::CoreList> has been upgraded from version 2.66 to 2.67. |
| 125 | |
| 126 | =item * |
| 127 | |
| 128 | L<overload> has been upgraded from version 1.18 to 1.19. |
| 129 | |
| 130 | C<no overload> now warns for invalid arguments, just like C<use overload>. |
| 131 | |
| 132 | =item * |
| 133 | |
| 134 | L<Pod::Functions> has been upgraded from version 1.05 to 1.06. |
| 135 | |
| 136 | Typo fix in generated documentation. |
| 137 | |
| 138 | =item * |
| 139 | |
| 140 | L<Storable> has been upgraded from version 2.34 to 2.35. |
| 141 | |
| 142 | Modifying C<$_[0]> within C<STORABLE_freeze> no longer results in crashes |
| 143 | [perl #112358]. |
| 144 | |
| 145 | An object whose class implements C<STORABLE_attach> is now thawed only once |
| 146 | when there are multiple references to it in the structure being thawed |
| 147 | [perl #111918]. |
| 148 | |
| 149 | =item * |
| 150 | |
| 151 | L<utf8> has been upgraded from version 1.09 to 1.10. |
| 152 | |
| 153 | Some documentation has been clarified. |
| 154 | |
| 155 | =back |
| 156 | |
| 157 | =head2 Removed Modules and Pragmata |
| 158 | |
| 159 | =over 4 |
| 160 | |
| 161 | =item * |
| 162 | |
| 163 | L<Version::Requirements> has been removed from the core distribution. It is |
| 164 | available under a different name: L<CPAN::Meta::Requirements>. |
| 165 | |
| 166 | =back |
| 167 | |
| 168 | =head1 Documentation |
| 169 | |
| 170 | =head2 Changes to Existing Documentation |
| 171 | |
| 172 | =head3 L<perldata> |
| 173 | |
| 174 | =over 4 |
| 175 | |
| 176 | =item * |
| 177 | |
| 178 | Now explicitly documents the behaviour of hash initializer lists that |
| 179 | contain duplicate keys. |
| 180 | |
| 181 | =back |
| 182 | |
| 183 | =head3 L<perldiag> |
| 184 | |
| 185 | =over 4 |
| 186 | |
| 187 | =item * |
| 188 | |
| 189 | The explanation of symbolic references being prevented by "strict refs" |
| 190 | now doesn't assume that the reader knows what symbolic references are. |
| 191 | |
| 192 | =back |
| 193 | |
| 194 | =head3 L<perlfunc> |
| 195 | |
| 196 | =over 4 |
| 197 | |
| 198 | =item * |
| 199 | |
| 200 | The return value of C<pipe> is now documented. |
| 201 | |
| 202 | =back |
| 203 | |
| 204 | =head1 Diagnostics |
| 205 | |
| 206 | The following additions or changes have been made to diagnostic output, |
| 207 | including warnings and fatal error messages. For the complete list of |
| 208 | diagnostic messages, see L<perldiag>. |
| 209 | |
| 210 | =head2 New Diagnostics |
| 211 | |
| 212 | =head3 New Warnings |
| 213 | |
| 214 | =over 4 |
| 215 | |
| 216 | =item * |
| 217 | |
| 218 | "L<Unescaped left brace in regex is deprecated, passed |
| 219 | through|perldiag/"Unescaped left brace in regex is deprecated, passed |
| 220 | through">" is a new deprecation warning. See L</Unescaped braces in |
| 221 | regexps>. |
| 222 | |
| 223 | =back |
| 224 | |
| 225 | =head1 Testing |
| 226 | |
| 227 | =over 4 |
| 228 | |
| 229 | =item * |
| 230 | |
| 231 | The test suite now has a section for tests that require very large amounts |
| 232 | of memory. These tests won't run by default; they can be enabled by |
| 233 | setting the C<PERL_TEST_MEMORY> environment variable to the number of |
| 234 | gibibytes of memory that may be safely used. |
| 235 | |
| 236 | =back |
| 237 | |
| 238 | =head1 Platform Support |
| 239 | |
| 240 | =head2 Platform-Specific Notes |
| 241 | |
| 242 | =over 4 |
| 243 | |
| 244 | =item clang++ |
| 245 | |
| 246 | There is now a workaround for a compiler bug that prevented compiling |
| 247 | with clang++ since Perl 5.15.7 [perl #112786]. |
| 248 | |
| 249 | =item C++ |
| 250 | |
| 251 | When compiling the Perl core as C++ (which is only semi-supported), the |
| 252 | mathom functions are now compiled as C<extern "C">, to ensure proper |
| 253 | binary compatibility. (However, binary compatibility isn't generally |
| 254 | guaranteed anyway in the situations where this would matter.) |
| 255 | |
| 256 | =item VMS |
| 257 | |
| 258 | It should now be possible to compile Perl as C++ on VMS. |
| 259 | |
| 260 | =back |
| 261 | |
| 262 | =head1 Internal Changes |
| 263 | |
| 264 | =over 4 |
| 265 | |
| 266 | =item * |
| 267 | |
| 268 | The C<CV *> typemap entry now supports C<&{}> overloading and typeglobs, |
| 269 | just like C<&{...}> [perl #96872]. |
| 270 | |
| 271 | =item * |
| 272 | |
| 273 | The C<SVf_AMAGIC> flag to indicate overloading is now on the stash, not the |
| 274 | object. It is now set automatically whenever a method or @ISA changes, so |
| 275 | its meaning has changed, too. It now means "potentially overloaded". When |
| 276 | the overload table is calculated, the flag is automatically turned off if |
| 277 | there is no overloading, so there should be no noticeable slowdown. |
| 278 | |
| 279 | The staleness of the overload tables is now checked when overload methods |
| 280 | are invoked, rather than during C<bless>. |
| 281 | |
| 282 | "A" magic is gone. The changes to the handling of the C<SVf_AMAGIC> flag |
| 283 | eliminate the need for it. |
| 284 | |
| 285 | C<PL_amagic_generation> has been removed as no longer necessary. For XS |
| 286 | modules, it is now a macro alias to C<PL_na>. |
| 287 | |
| 288 | The fallback overload setting is now stored in a stash entry separate from |
| 289 | overloadedness itself. |
| 290 | |
| 291 | =item * |
| 292 | |
| 293 | The character-processing code has been cleaned up in places. The changes |
| 294 | should be operationally invisible. |
| 295 | |
| 296 | =back |
| 297 | |
| 298 | =head1 Selected Bug Fixes |
| 299 | |
| 300 | =over 4 |
| 301 | |
| 302 | =item * |
| 303 | |
| 304 | C<goto ''> now looks for an empty label, producing the "goto must have |
| 305 | label" error message, instead of exiting the program [perl #111794]. |
| 306 | |
| 307 | =item * |
| 308 | |
| 309 | C<goto "\0"> now dies with "Can't find label" instead of "goto must have |
| 310 | label". |
| 311 | |
| 312 | =item * |
| 313 | |
| 314 | The C function C<hv_store> used to result in crashes when used on C<%^H> |
| 315 | [perl #111000]. |
| 316 | |
| 317 | =item * |
| 318 | |
| 319 | A call checker attached to a closure prototype via C<cv_set_call_checker> |
| 320 | is now copied to closures cloned from it. So C<cv_set_call_checker> now |
| 321 | works inside an attribute handler for a closure. |
| 322 | |
| 323 | =item * |
| 324 | |
| 325 | Writing to C<$^N> used to have no effect. Now it croaks with "Modification |
| 326 | of a read-only value" by default, but that can be overridden by a custom |
| 327 | regular expression engine, as with C<$1> [perl #112184]. |
| 328 | |
| 329 | =item * |
| 330 | |
| 331 | C<undef> on a control character glob (C<undef *^H>) no longer emits an |
| 332 | erroneous warning about ambiguity [perl #112456]. |
| 333 | |
| 334 | =item * |
| 335 | |
| 336 | For efficiency's sake, many operators and built-in functions return the |
| 337 | same scalar each time. Lvalue subroutines and subroutines in the CORE:: |
| 338 | namespace were allowing this implementation detail to leak through. |
| 339 | C<print &CORE::uc("a"), &CORE::uc("b")> used to print "BB". The same thing |
| 340 | would happen with an lvalue subroutine returning the return value of C<uc>. |
| 341 | Now the value is copied in such cases. |
| 342 | |
| 343 | =item * |
| 344 | |
| 345 | C<method {}> syntax with an empty block or a block returning an empty list |
| 346 | used to crash or use some random value left on the stack as its invocant. |
| 347 | Now it produces an error. |
| 348 | |
| 349 | =item * |
| 350 | |
| 351 | C<vec> now works with extremely large offsets (E<gt>2 GB) [perl #111730]. |
| 352 | |
| 353 | =item * |
| 354 | |
| 355 | Changes to overload settings now take effect immediately, as do changes to |
| 356 | inheritance that affect overloading. They used to take effect only after |
| 357 | C<bless>. |
| 358 | |
| 359 | Objects that were created before a class had any overloading used to remain |
| 360 | non-overloaded even if the class gained overloading through C<use overload> |
| 361 | or @ISA changes, and even after C<bless>. This has been fixed |
| 362 | [perl #112708]. |
| 363 | |
| 364 | =item * |
| 365 | |
| 366 | Classes with overloading can now inherit fallback values. |
| 367 | |
| 368 | =item * |
| 369 | |
| 370 | Overloading was not respecting a fallback value of 0 if there were |
| 371 | overloaded objects on both sides of an assignment operator like C<+=> |
| 372 | [perl #111856]. |
| 373 | |
| 374 | =item * |
| 375 | |
| 376 | C<pos> now croaks with hash and array arguments, instead of producing |
| 377 | erroneous warnings. |
| 378 | |
| 379 | =item * |
| 380 | |
| 381 | C<while(each %h)> now implies C<while(defined($_ = each %h))>, like |
| 382 | C<readline> and C<readdir>. |
| 383 | |
| 384 | =item * |
| 385 | |
| 386 | Subs in the CORE:: namespace no longer crash after C<undef *_> when called |
| 387 | with no argument list (C<&CORE::time> with no parentheses). |
| 388 | |
| 389 | =item * |
| 390 | |
| 391 | Unicode 6.1 published an incorrect alias for one of the |
| 392 | Canonical_Combining_Class property's values (which range between 0 and |
| 393 | 254). The alias C<CCC133> should have been C<CCC132>. Perl now |
| 394 | overrides the data file furnished by Unicode to give the correct value. |
| 395 | |
| 396 | =item * |
| 397 | |
| 398 | C<unpack> no longer produces the "'/' must follow a numeric type in unpack" |
| 399 | error when it is the data that are at fault [perl #60204]. |
| 400 | |
| 401 | =item * |
| 402 | |
| 403 | C<join> and C<"@array"> now call FETCH only once on a tied C<$"> |
| 404 | [perl #8931]. |
| 405 | |
| 406 | =item * |
| 407 | |
| 408 | Some subroutine calls generated by compiling core ops affected by a |
| 409 | C<CORE::GLOBAL> override had op checking performed twice. The checking |
| 410 | is always idempotent for pure Perl code, but the double checking can |
| 411 | matter when custom call checkers are involved. |
| 412 | |
| 413 | =item * |
| 414 | |
| 415 | A race condition used to exist around fork that could cause a signal sent to |
| 416 | the parent to be handled by both parent and child. Signals are now blocked |
| 417 | briefly around fork to prevent this from happening [perl #82580]. |
| 418 | |
| 419 | =back |
| 420 | |
| 421 | =head1 Acknowledgements |
| 422 | |
| 423 | Perl 5.17.0 represents approximately 1 week of development since Perl 5.16.0 |
| 424 | and contains approximately 17,000 lines of changes across 180 files from 26 |
| 425 | authors. |
| 426 | |
| 427 | Perl continues to flourish into its third decade thanks to a vibrant community |
| 428 | of users and developers. The following people are known to have contributed the |
| 429 | improvements that became Perl 5.16.1: |
| 430 | |
| 431 | Alan Haggai Alavi, Aristotle Pagaltzis, Brian Fraser, Chris 'BinGOs' Williams, |
| 432 | Craig A. Berry, Dagfinn Ilmari Mannsåker, Eric Brine, Father Chrysostomos, |
| 433 | Igor Zaytsev, James E Keenan, Karl Williamson, Leon Timmermans, Lukas Mai, |
| 434 | Marcus Holland-Moritz, Matthew Horsfall, Moritz Lenz, Rafael Garcia-Suarez, |
| 435 | Reini Urban, Ricardo Signes, Robin Barker, Ronald J. Kimball, Smylers, Steffen |
| 436 | Müller, Steve Hay, Tony Cook, Zefram. |
| 437 | |
| 438 | The list above is almost certainly incomplete as it is automatically generated |
| 439 | from version control history. In particular, it does not include the names of |
| 440 | the (very much appreciated) contributors who reported issues to the Perl bug |
| 441 | tracker. |
| 442 | |
| 443 | Many of the changes included in this version originated in the CPAN modules |
| 444 | included in Perl's core. We're grateful to the entire CPAN community for |
| 445 | helping Perl to flourish. |
| 446 | |
| 447 | For a more complete list of all of Perl's historical contributors, please see |
| 448 | the F<AUTHORS> file in the Perl source distribution. |
| 449 | |
| 450 | =head1 Reporting Bugs |
| 451 | |
| 452 | If you find what you think is a bug, you might check the articles |
| 453 | recently posted to the comp.lang.perl.misc newsgroup and the perl |
| 454 | bug database at http://rt.perl.org/perlbug/ . There may also be |
| 455 | information at http://www.perl.org/ , the Perl Home Page. |
| 456 | |
| 457 | If you believe you have an unreported bug, please run the L<perlbug> |
| 458 | program included with your release. Be sure to trim your bug down |
| 459 | to a tiny but sufficient test case. Your bug report, along with the |
| 460 | output of C<perl -V>, will be sent off to perlbug@perl.org to be |
| 461 | analysed by the Perl porting team. |
| 462 | |
| 463 | If the bug you are reporting has security implications, which make it |
| 464 | inappropriate to send to a publicly archived mailing list, then please send |
| 465 | it to perl5-security-report@perl.org. This points to a closed subscription |
| 466 | unarchived mailing list, which includes |
| 467 | all the core committers, who will be able |
| 468 | to help assess the impact of issues, figure out a resolution, and help |
| 469 | co-ordinate the release of patches to mitigate or fix the problem across all |
| 470 | platforms on which Perl is supported. Please only use this address for |
| 471 | security issues in the Perl core, not for modules independently |
| 472 | distributed on CPAN. |
| 473 | |
| 474 | =head1 SEE ALSO |
| 475 | |
| 476 | The F<Changes> file for an explanation of how to view exhaustive details |
| 477 | on what changed. |
| 478 | |
| 479 | The F<INSTALL> file for how to build Perl. |
| 480 | |
| 481 | The F<README> file for general stuff. |
| 482 | |
| 483 | The F<Artistic> and F<Copying> files for copyright information. |
| 484 | |
| 485 | =cut |