| 1 | =head1 NAME |
| 2 | |
| 3 | perltodo - Perl TO-DO List |
| 4 | |
| 5 | =head1 DESCRIPTION |
| 6 | |
| 7 | This is a list of wishes for Perl. The tasks we think are smaller or easier |
| 8 | are listed first. Anyone is welcome to work on any of these, but it's a good |
| 9 | idea to first contact I<perl5-porters@perl.org> to avoid duplication of |
| 10 | effort. By all means contact a pumpking privately first if you prefer. |
| 11 | |
| 12 | Whilst patches to make the list shorter are most welcome, ideas to add to |
| 13 | the list are also encouraged. Check the perl5-porters archives for past |
| 14 | ideas, and any discussion about them. One set of archives may be found at: |
| 15 | |
| 16 | http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/ |
| 17 | |
| 18 | What can we offer you in return? Fame, fortune, and everlasting glory? Maybe |
| 19 | not, but if your patch is incorporated, then we'll add your name to the |
| 20 | F<AUTHORS> file, which ships in the official distribution. How many other |
| 21 | programming languages offer you 1 line of immortality? |
| 22 | |
| 23 | =head1 Tasks that only need Perl knowledge |
| 24 | |
| 25 | =head2 common test code for timed bail out |
| 26 | |
| 27 | Write portable self destruct code for tests to stop them burning CPU in |
| 28 | infinite loops. This needs to avoid using alarm, as some of the tests are |
| 29 | testing alarm/sleep or timers. |
| 30 | |
| 31 | =head2 POD -E<gt> HTML conversion in the core still sucks |
| 32 | |
| 33 | Which is crazy given just how simple POD purports to be, and how simple HTML |
| 34 | can be. It's not actually I<as> simple as it sounds, particularly with the |
| 35 | flexibility POD allows for C<=item>, but it would be good to improve the |
| 36 | visual appeal of the HTML generated, and to avoid it having any validation |
| 37 | errors. See also L</make HTML install work>, as the layout of installation tree |
| 38 | is needed to improve the cross-linking. |
| 39 | |
| 40 | The addition of C<Pod::Simple> and its related modules may make this task |
| 41 | easier to complete. |
| 42 | |
| 43 | =head2 Parallel testing |
| 44 | |
| 45 | (This probably impacts much more than the core: also the Test::Harness |
| 46 | and TAP::* modules on CPAN.) |
| 47 | |
| 48 | The core regression test suite is getting ever more comprehensive, which has |
| 49 | the side effect that it takes longer to run. This isn't so good. Investigate |
| 50 | whether it would be feasible to give the harness script the B<option> of |
| 51 | running sets of tests in parallel. This would be useful for tests in |
| 52 | F<t/op/*.t> and F<t/uni/*.t> and maybe some sets of tests in F<lib/>. |
| 53 | |
| 54 | Questions to answer |
| 55 | |
| 56 | =over 4 |
| 57 | |
| 58 | =item 1 |
| 59 | |
| 60 | How does screen layout work when you're running more than one test? |
| 61 | |
| 62 | =item 2 |
| 63 | |
| 64 | How does the caller of test specify how many tests to run in parallel? |
| 65 | |
| 66 | =item 3 |
| 67 | |
| 68 | How do setup/teardown tests identify themselves? |
| 69 | |
| 70 | =back |
| 71 | |
| 72 | Pugs already does parallel testing - can their approach be re-used? |
| 73 | |
| 74 | =head2 Make Schwern poorer |
| 75 | |
| 76 | We should have tests for everything. When all the core's modules are tested, |
| 77 | Schwern has promised to donate to $500 to TPF. We may need volunteers to |
| 78 | hold him upside down and shake vigorously in order to actually extract the |
| 79 | cash. |
| 80 | |
| 81 | =head2 Improve the coverage of the core tests |
| 82 | |
| 83 | Use Devel::Cover to ascertain the core modules's test coverage, then add |
| 84 | tests that are currently missing. |
| 85 | |
| 86 | =head2 test B |
| 87 | |
| 88 | A full test suite for the B module would be nice. |
| 89 | |
| 90 | =head2 Deparse inlined constants |
| 91 | |
| 92 | Code such as this |
| 93 | |
| 94 | use constant PI => 4; |
| 95 | warn PI |
| 96 | |
| 97 | will currently deparse as |
| 98 | |
| 99 | use constant ('PI', 4); |
| 100 | warn 4; |
| 101 | |
| 102 | because the tokenizer inlines the value of the constant subroutine C<PI>. |
| 103 | This allows various compile time optimisations, such as constant folding |
| 104 | and dead code elimination. Where these haven't happened (such as the example |
| 105 | above) it ought be possible to make B::Deparse work out the name of the |
| 106 | original constant, because just enough information survives in the symbol |
| 107 | table to do this. Specifically, the same scalar is used for the constant in |
| 108 | the optree as is used for the constant subroutine, so by iterating over all |
| 109 | symbol tables and generating a mapping of SV address to constant name, it |
| 110 | would be possible to provide B::Deparse with this functionality. |
| 111 | |
| 112 | =head2 A decent benchmark |
| 113 | |
| 114 | C<perlbench> seems impervious to any recent changes made to the perl core. It |
| 115 | would be useful to have a reasonable general benchmarking suite that roughly |
| 116 | represented what current perl programs do, and measurably reported whether |
| 117 | tweaks to the core improve, degrade or don't really affect performance, to |
| 118 | guide people attempting to optimise the guts of perl. Gisle would welcome |
| 119 | new tests for perlbench. |
| 120 | |
| 121 | =head2 fix tainting bugs |
| 122 | |
| 123 | Fix the bugs revealed by running the test suite with the C<-t> switch (via |
| 124 | C<make test.taintwarn>). |
| 125 | |
| 126 | =head2 Dual life everything |
| 127 | |
| 128 | As part of the "dists" plan, anything that doesn't belong in the smallest perl |
| 129 | distribution needs to be dual lifed. Anything else can be too. Figure out what |
| 130 | changes would be needed to package that module and its tests up for CPAN, and |
| 131 | do so. Test it with older perl releases, and fix the problems you find. |
| 132 | |
| 133 | To make a minimal perl distribution, it's useful to look at |
| 134 | F<t/lib/commonsense.t>. |
| 135 | |
| 136 | =head2 Improving C<threads::shared> |
| 137 | |
| 138 | Investigate whether C<threads::shared> could share aggregates properly with |
| 139 | only Perl level changes to shared.pm |
| 140 | |
| 141 | =head2 POSIX memory footprint |
| 142 | |
| 143 | Ilya observed that use POSIX; eats memory like there's no tomorrow, and at |
| 144 | various times worked to cut it down. There is probably still fat to cut out - |
| 145 | for example POSIX passes Exporter some very memory hungry data structures. |
| 146 | |
| 147 | =head2 embed.pl/makedef.pl |
| 148 | |
| 149 | There is a script F<embed.pl> that generates several header files to prefix |
| 150 | all of Perl's symbols in a consistent way, to provide some semblance of |
| 151 | namespace support in C<C>. Functions are declared in F<embed.fnc>, variables |
| 152 | in F<interpvar.h>. Quite a few of the functions and variables |
| 153 | are conditionally declared there, using C<#ifdef>. However, F<embed.pl> |
| 154 | doesn't understand the C macros, so the rules about which symbols are present |
| 155 | when is duplicated in F<makedef.pl>. Writing things twice is bad, m'kay. |
| 156 | It would be good to teach C<embed.pl> to understand the conditional |
| 157 | compilation, and hence remove the duplication, and the mistakes it has caused. |
| 158 | |
| 159 | =head2 use strict; and AutoLoad |
| 160 | |
| 161 | Currently if you write |
| 162 | |
| 163 | package Whack; |
| 164 | use AutoLoader 'AUTOLOAD'; |
| 165 | use strict; |
| 166 | 1; |
| 167 | __END__ |
| 168 | sub bloop { |
| 169 | print join (' ', No, strict, here), "!\n"; |
| 170 | } |
| 171 | |
| 172 | then C<use strict;> isn't in force within the autoloaded subroutines. It would |
| 173 | be more consistent (and less surprising) to arrange for all lexical pragmas |
| 174 | in force at the __END__ block to be in force within each autoloaded subroutine. |
| 175 | |
| 176 | There's a similar problem with SelfLoader. |
| 177 | |
| 178 | =head1 Tasks that need a little sysadmin-type knowledge |
| 179 | |
| 180 | Or if you prefer, tasks that you would learn from, and broaden your skills |
| 181 | base... |
| 182 | |
| 183 | =head2 make HTML install work |
| 184 | |
| 185 | There is an C<installhtml> target in the Makefile. It's marked as |
| 186 | "experimental". It would be good to get this tested, make it work reliably, and |
| 187 | remove the "experimental" tag. This would include |
| 188 | |
| 189 | =over 4 |
| 190 | |
| 191 | =item 1 |
| 192 | |
| 193 | Checking that cross linking between various parts of the documentation works. |
| 194 | In particular that links work between the modules (files with POD in F<lib/>) |
| 195 | and the core documentation (files in F<pod/>) |
| 196 | |
| 197 | =item 2 |
| 198 | |
| 199 | Work out how to split C<perlfunc> into chunks, preferably one per function |
| 200 | group, preferably with general case code that could be used elsewhere. |
| 201 | Challenges here are correctly identifying the groups of functions that go |
| 202 | together, and making the right named external cross-links point to the right |
| 203 | page. Things to be aware of are C<-X>, groups such as C<getpwnam> to |
| 204 | C<endservent>, two or more C<=items> giving the different parameter lists, such |
| 205 | as |
| 206 | |
| 207 | =item substr EXPR,OFFSET,LENGTH,REPLACEMENT |
| 208 | =item substr EXPR,OFFSET,LENGTH |
| 209 | =item substr EXPR,OFFSET |
| 210 | |
| 211 | and different parameter lists having different meanings. (eg C<select>) |
| 212 | |
| 213 | =back |
| 214 | |
| 215 | =head2 compressed man pages |
| 216 | |
| 217 | Be able to install them. This would probably need a configure test to see how |
| 218 | the system does compressed man pages (same directory/different directory? |
| 219 | same filename/different filename), as well as tweaking the F<installman> script |
| 220 | to compress as necessary. |
| 221 | |
| 222 | =head2 Add a code coverage target to the Makefile |
| 223 | |
| 224 | Make it easy for anyone to run Devel::Cover on the core's tests. The steps |
| 225 | to do this manually are roughly |
| 226 | |
| 227 | =over 4 |
| 228 | |
| 229 | =item * |
| 230 | |
| 231 | do a normal C<Configure>, but include Devel::Cover as a module to install |
| 232 | (see F<INSTALL> for how to do this) |
| 233 | |
| 234 | =item * |
| 235 | |
| 236 | make perl |
| 237 | |
| 238 | =item * |
| 239 | |
| 240 | cd t; HARNESS_PERL_SWITCHES=-MDevel::Cover ./perl -I../lib harness |
| 241 | |
| 242 | =item * |
| 243 | |
| 244 | Process the resulting Devel::Cover database |
| 245 | |
| 246 | =back |
| 247 | |
| 248 | This just give you the coverage of the F<.pm>s. To also get the C level |
| 249 | coverage you need to |
| 250 | |
| 251 | =over 4 |
| 252 | |
| 253 | =item * |
| 254 | |
| 255 | Additionally tell C<Configure> to use the appropriate C compiler flags for |
| 256 | C<gcov> |
| 257 | |
| 258 | =item * |
| 259 | |
| 260 | make perl.gcov |
| 261 | |
| 262 | (instead of C<make perl>) |
| 263 | |
| 264 | =item * |
| 265 | |
| 266 | After running the tests run C<gcov> to generate all the F<.gcov> files. |
| 267 | (Including down in the subdirectories of F<ext/> |
| 268 | |
| 269 | =item * |
| 270 | |
| 271 | (From the top level perl directory) run C<gcov2perl> on all the C<.gcov> files |
| 272 | to get their stats into the cover_db directory. |
| 273 | |
| 274 | =item * |
| 275 | |
| 276 | Then process the Devel::Cover database |
| 277 | |
| 278 | =back |
| 279 | |
| 280 | It would be good to add a single switch to C<Configure> to specify that you |
| 281 | wanted to perform perl level coverage, and another to specify C level |
| 282 | coverage, and have C<Configure> and the F<Makefile> do all the right things |
| 283 | automatically. |
| 284 | |
| 285 | =head2 Make Config.pm cope with differences between built and installed perl |
| 286 | |
| 287 | Quite often vendors ship a perl binary compiled with their (pay-for) |
| 288 | compilers. People install a free compiler, such as gcc. To work out how to |
| 289 | build extensions, Perl interrogates C<%Config>, so in this situation |
| 290 | C<%Config> describes compilers that aren't there, and extension building |
| 291 | fails. This forces people into choosing between re-compiling perl themselves |
| 292 | using the compiler they have, or only using modules that the vendor ships. |
| 293 | |
| 294 | It would be good to find a way teach C<Config.pm> about the installation setup, |
| 295 | possibly involving probing at install time or later, so that the C<%Config> in |
| 296 | a binary distribution better describes the installed machine, when the |
| 297 | installed machine differs from the build machine in some significant way. |
| 298 | |
| 299 | =head2 linker specification files |
| 300 | |
| 301 | Some platforms mandate that you provide a list of a shared library's external |
| 302 | symbols to the linker, so the core already has the infrastructure in place to |
| 303 | do this for generating shared perl libraries. My understanding is that the |
| 304 | GNU toolchain can accept an optional linker specification file, and restrict |
| 305 | visibility just to symbols declared in that file. It would be good to extend |
| 306 | F<makedef.pl> to support this format, and to provide a means within |
| 307 | C<Configure> to enable it. This would allow Unix users to test that the |
| 308 | export list is correct, and to build a perl that does not pollute the global |
| 309 | namespace with private symbols. |
| 310 | |
| 311 | =head2 Cross-compile support |
| 312 | |
| 313 | Currently C<Configure> understands C<-Dusecrosscompile> option. This option |
| 314 | arranges for building C<miniperl> for TARGET machine, so this C<miniperl> is |
| 315 | assumed then to be copied to TARGET machine and used as a replacement of full |
| 316 | C<perl> executable. |
| 317 | |
| 318 | This could be done little differently. Namely C<miniperl> should be built for |
| 319 | HOST and then full C<perl> with extensions should be compiled for TARGET. |
| 320 | This, however, might require extra trickery for %Config: we have one config |
| 321 | first for HOST and then another for TARGET. Tools like MakeMaker will be |
| 322 | mightily confused. Having around two different types of executables and |
| 323 | libraries (HOST and TARGET) makes life interesting for Makefiles and |
| 324 | shell (and Perl) scripts. There is $Config{run}, normally empty, which |
| 325 | can be used as an execution wrapper. Also note that in some |
| 326 | cross-compilation/execution environments the HOST and the TARGET do |
| 327 | not see the same filesystem(s), the $Config{run} may need to do some |
| 328 | file/directory copying back and forth. |
| 329 | |
| 330 | =head1 Tasks that need a little C knowledge |
| 331 | |
| 332 | These tasks would need a little C knowledge, but don't need any specific |
| 333 | background or experience with XS, or how the Perl interpreter works |
| 334 | |
| 335 | =head2 Modernize the order of directories in @INC |
| 336 | |
| 337 | The way @INC is laid out by default, one cannot upgrade core (dual-life) |
| 338 | modules without overwriting files. This causes problems for binary |
| 339 | package builders. One possible proposal is laid out in this |
| 340 | message: |
| 341 | L<http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/2002-04/msg02380.html>. |
| 342 | |
| 343 | =head2 -Duse32bit* |
| 344 | |
| 345 | Natively 64-bit systems need neither -Duse64bitint nor -Duse64bitall. |
| 346 | On these systems, it might be the default compilation mode, and there |
| 347 | is currently no guarantee that passing no use64bitall option to the |
| 348 | Configure process will build a 32bit perl. Implementing -Duse32bit* |
| 349 | options would be nice for perl 5.12. |
| 350 | |
| 351 | =head2 Make it clear from -v if this is the exact official release |
| 352 | |
| 353 | Currently perl from C<p4>/C<rsync> ships with a F<patchlevel.h> file that |
| 354 | usually defines one local patch, of the form "MAINT12345" or "RC1". The output |
| 355 | of perl -v doesn't report that a perl isn't an official release, and this |
| 356 | information can get lost in bugs reports. Because of this, the minor version |
| 357 | isn't bumped up until RC time, to minimise the possibility of versions of perl |
| 358 | escaping that believe themselves to be newer than they actually are. |
| 359 | |
| 360 | It would be useful to find an elegant way to have the "this is an interim |
| 361 | maintenance release" or "this is a release candidate" in the terse -v output, |
| 362 | and have it so that it's easy for the pumpking to remove this just as the |
| 363 | release tarball is rolled up. This way the version pulled out of rsync would |
| 364 | always say "I'm a development release" and it would be safe to bump the |
| 365 | reported minor version as soon as a release ships, which would aid perl |
| 366 | developers. |
| 367 | |
| 368 | This task is really about thinking of an elegant way to arrange the C source |
| 369 | such that it's trivial for the Pumpking to flag "this is an official release" |
| 370 | when making a tarball, yet leave the default source saying "I'm not the |
| 371 | official release". |
| 372 | |
| 373 | =head2 Profile Perl - am I hot or not? |
| 374 | |
| 375 | The Perl source code is stable enough that it makes sense to profile it, |
| 376 | identify and optimise the hotspots. It would be good to measure the |
| 377 | performance of the Perl interpreter using free tools such as cachegrind, |
| 378 | gprof, and dtrace, and work to reduce the bottlenecks they reveal. |
| 379 | |
| 380 | As part of this, the idea of F<pp_hot.c> is that it contains the I<hot> ops, |
| 381 | the ops that are most commonly used. The idea is that by grouping them, their |
| 382 | object code will be adjacent in the executable, so they have a greater chance |
| 383 | of already being in the CPU cache (or swapped in) due to being near another op |
| 384 | already in use. |
| 385 | |
| 386 | Except that it's not clear if these really are the most commonly used ops. So |
| 387 | as part of exercising your skills with coverage and profiling tools you might |
| 388 | want to determine what ops I<really> are the most commonly used. And in turn |
| 389 | suggest evictions and promotions to achieve a better F<pp_hot.c>. |
| 390 | |
| 391 | =head2 Allocate OPs from arenas |
| 392 | |
| 393 | Currently all new OP structures are individually malloc()ed and free()d. |
| 394 | All C<malloc> implementations have space overheads, and are now as fast as |
| 395 | custom allocates so it would both use less memory and less CPU to allocate |
| 396 | the various OP structures from arenas. The SV arena code can probably be |
| 397 | re-used for this. |
| 398 | |
| 399 | Note that Configuring perl with C<-Accflags=-DPL_OP_SLAB_ALLOC> will use |
| 400 | Perl_Slab_alloc() to pack optrees into a contiguous block, which is |
| 401 | probably superior to the use of OP arenas, esp. from a cache locality |
| 402 | standpoint. See L<Profile Perl - am I hot or not?>. |
| 403 | |
| 404 | =head2 Improve win32/wince.c |
| 405 | |
| 406 | Currently, numerous functions look virtually, if not completely, |
| 407 | identical in both C<win32/wince.c> and C<win32/win32.c> files, which can't |
| 408 | be good. |
| 409 | |
| 410 | =head2 Use secure CRT functions when building with VC8 on Win32 |
| 411 | |
| 412 | Visual C++ 2005 (VC++ 8.x) deprecated a number of CRT functions on the basis |
| 413 | that they were "unsafe" and introduced differently named secure versions of |
| 414 | them as replacements, e.g. instead of writing |
| 415 | |
| 416 | FILE* f = fopen(__FILE__, "r"); |
| 417 | |
| 418 | one should now write |
| 419 | |
| 420 | FILE* f; |
| 421 | errno_t err = fopen_s(&f, __FILE__, "r"); |
| 422 | |
| 423 | Currently, the warnings about these deprecations have been disabled by adding |
| 424 | -D_CRT_SECURE_NO_DEPRECATE to the CFLAGS. It would be nice to remove that |
| 425 | warning suppressant and actually make use of the new secure CRT functions. |
| 426 | |
| 427 | There is also a similar issue with POSIX CRT function names like fileno having |
| 428 | been deprecated in favour of ISO C++ conformant names like _fileno. These |
| 429 | warnings are also currently suppressed by adding -D_CRT_NONSTDC_NO_DEPRECATE. It |
| 430 | might be nice to do as Microsoft suggest here too, although, unlike the secure |
| 431 | functions issue, there is presumably little or no benefit in this case. |
| 432 | |
| 433 | =head2 __FUNCTION__ for MSVC-pre-7.0 |
| 434 | |
| 435 | Jarkko notes that one can things morally equivalent to C<__FUNCTION__> |
| 436 | (or C<__func__>) even in MSVC-pre-7.0, contrary to popular belief. |
| 437 | See L<http://www.codeproject.com/debug/extendedtrace.asp> if you feel like |
| 438 | making C<PERL_MEM_LOG> more useful on Win32. |
| 439 | |
| 440 | =head1 Tasks that need a knowledge of XS |
| 441 | |
| 442 | These tasks would need C knowledge, and roughly the level of knowledge of |
| 443 | the perl API that comes from writing modules that use XS to interface to |
| 444 | C. |
| 445 | |
| 446 | =head2 autovivification |
| 447 | |
| 448 | Make all autovivification consistent w.r.t LVALUE/RVALUE and strict/no strict; |
| 449 | |
| 450 | This task is incremental - even a little bit of work on it will help. |
| 451 | |
| 452 | =head2 Unicode in Filenames |
| 453 | |
| 454 | chdir, chmod, chown, chroot, exec, glob, link, lstat, mkdir, open, |
| 455 | opendir, qx, readdir, readlink, rename, rmdir, stat, symlink, sysopen, |
| 456 | system, truncate, unlink, utime, -X. All these could potentially accept |
| 457 | Unicode filenames either as input or output (and in the case of system |
| 458 | and qx Unicode in general, as input or output to/from the shell). |
| 459 | Whether a filesystem - an operating system pair understands Unicode in |
| 460 | filenames varies. |
| 461 | |
| 462 | Known combinations that have some level of understanding include |
| 463 | Microsoft NTFS, Apple HFS+ (In Mac OS 9 and X) and Apple UFS (in Mac |
| 464 | OS X), NFS v4 is rumored to be Unicode, and of course Plan 9. How to |
| 465 | create Unicode filenames, what forms of Unicode are accepted and used |
| 466 | (UCS-2, UTF-16, UTF-8), what (if any) is the normalization form used, |
| 467 | and so on, varies. Finding the right level of interfacing to Perl |
| 468 | requires some thought. Remember that an OS does not implicate a |
| 469 | filesystem. |
| 470 | |
| 471 | (The Windows -C command flag "wide API support" has been at least |
| 472 | temporarily retired in 5.8.1, and the -C has been repurposed, see |
| 473 | L<perlrun>.) |
| 474 | |
| 475 | Most probably the right way to do this would be this: |
| 476 | L</"Virtualize operating system access">. |
| 477 | |
| 478 | =head2 Unicode in %ENV |
| 479 | |
| 480 | Currently the %ENV entries are always byte strings. |
| 481 | See L</"Virtualize operating system access">. |
| 482 | |
| 483 | =head2 Unicode and glob() |
| 484 | |
| 485 | Currently glob patterns and filenames returned from File::Glob::glob() |
| 486 | are always byte strings. See L</"Virtualize operating system access">. |
| 487 | |
| 488 | =head2 Unicode and lc/uc operators |
| 489 | |
| 490 | Some built-in operators (C<lc>, C<uc>, etc.) behave differently, based on |
| 491 | what the internal encoding of their argument is. That should not be the |
| 492 | case. Maybe add a pragma to switch behaviour. |
| 493 | |
| 494 | =head2 use less 'memory' |
| 495 | |
| 496 | Investigate trade offs to switch out perl's choices on memory usage. |
| 497 | Particularly perl should be able to give memory back. |
| 498 | |
| 499 | This task is incremental - even a little bit of work on it will help. |
| 500 | |
| 501 | =head2 Re-implement C<:unique> in a way that is actually thread-safe |
| 502 | |
| 503 | The old implementation made bad assumptions on several levels. A good 90% |
| 504 | solution might be just to make C<:unique> work to share the string buffer |
| 505 | of SvPVs. That way large constant strings can be shared between ithreads, |
| 506 | such as the configuration information in F<Config>. |
| 507 | |
| 508 | =head2 Make tainting consistent |
| 509 | |
| 510 | Tainting would be easier to use if it didn't take documented shortcuts and |
| 511 | allow taint to "leak" everywhere within an expression. |
| 512 | |
| 513 | =head2 readpipe(LIST) |
| 514 | |
| 515 | system() accepts a LIST syntax (and a PROGRAM LIST syntax) to avoid |
| 516 | running a shell. readpipe() (the function behind qx//) could be similarly |
| 517 | extended. |
| 518 | |
| 519 | =head2 strcat(), strcpy(), strncat(), strncpy(), sprintf(), vsprintf() |
| 520 | |
| 521 | Maybe create a utility that checks after each libperl.a creation that |
| 522 | none of the above (nor sprintf(), vsprintf(), or *SHUDDER* gets()) |
| 523 | ever creep back to libperl.a. |
| 524 | |
| 525 | nm libperl.a | ./miniperl -alne '$o = $F[0] if /:$/; print "$o $F[1]" if $F[0] eq "U" && $F[1] =~ /^(?:strn?c(?:at|py)|v?sprintf|gets)$/' |
| 526 | |
| 527 | Note, of course, that this will only tell whether B<your> platform |
| 528 | is using those naughty interfaces. |
| 529 | |
| 530 | =head2 Audit the code for destruction ordering assumptions |
| 531 | |
| 532 | Change 25773 notes |
| 533 | |
| 534 | /* Need to check SvMAGICAL, as during global destruction it may be that |
| 535 | AvARYLEN(av) has been freed before av, and hence the SvANY() pointer |
| 536 | is now part of the linked list of SV heads, rather than pointing to |
| 537 | the original body. */ |
| 538 | /* FIXME - audit the code for other bugs like this one. */ |
| 539 | |
| 540 | adding the C<SvMAGICAL> check to |
| 541 | |
| 542 | if (AvARYLEN(av) && SvMAGICAL(AvARYLEN(av))) { |
| 543 | MAGIC *mg = mg_find (AvARYLEN(av), PERL_MAGIC_arylen); |
| 544 | |
| 545 | Go through the core and look for similar assumptions that SVs have particular |
| 546 | types, as all bets are off during global destruction. |
| 547 | |
| 548 | =head2 Extend PerlIO and PerlIO::Scalar |
| 549 | |
| 550 | PerlIO::Scalar doesn't know how to truncate(). Implementing this |
| 551 | would require extending the PerlIO vtable. |
| 552 | |
| 553 | Similarly the PerlIO vtable doesn't know about formats (write()), or |
| 554 | about stat(), or chmod()/chown(), utime(), or flock(). |
| 555 | |
| 556 | (For PerlIO::Scalar it's hard to see what e.g. mode bits or ownership |
| 557 | would mean.) |
| 558 | |
| 559 | PerlIO doesn't do directories or symlinks, either: mkdir(), rmdir(), |
| 560 | opendir(), closedir(), seekdir(), rewinddir(), glob(); symlink(), |
| 561 | readlink(). |
| 562 | |
| 563 | See also L</"Virtualize operating system access">. |
| 564 | |
| 565 | =head2 -C on the #! line |
| 566 | |
| 567 | It should be possible to make -C work correctly if found on the #! line, |
| 568 | given that all perl command line options are strict ASCII, and -C changes |
| 569 | only the interpretation of non-ASCII characters, and not for the script file |
| 570 | handle. To make it work needs some investigation of the ordering of function |
| 571 | calls during startup, and (by implication) a bit of tweaking of that order. |
| 572 | |
| 573 | |
| 574 | =head1 Tasks that need a knowledge of the interpreter |
| 575 | |
| 576 | These tasks would need C knowledge, and knowledge of how the interpreter works, |
| 577 | or a willingness to learn. |
| 578 | |
| 579 | =head2 state variable initialization in list context |
| 580 | |
| 581 | Currently this is illegal: |
| 582 | |
| 583 | state ($a, $b) = foo(); |
| 584 | |
| 585 | The current Perl 6 design is that C<state ($a) = foo();> and |
| 586 | C<(state $a) = foo();> have different semantics, which is tricky to implement |
| 587 | in Perl 5 as currently the produce the same opcode trees. It would be useful |
| 588 | to clarify that the Perl 6 design is firm, and then implement the necessary |
| 589 | code in Perl 5. There are comments in C<Perl_newASSIGNOP()> that show the |
| 590 | code paths taken by various assignment constructions involving state variables. |
| 591 | |
| 592 | =head2 Implement $value ~~ 0 .. $range |
| 593 | |
| 594 | It would be nice to extend the syntax of the C<~~> operator to also |
| 595 | understand numeric (and maybe alphanumeric) ranges. |
| 596 | |
| 597 | =head2 A does() built-in |
| 598 | |
| 599 | Like ref(), only useful. It would call the C<DOES> method on objects; it |
| 600 | would also tell whether something can be dereferenced as an |
| 601 | array/hash/etc., or used as a regexp, etc. |
| 602 | L<http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/2007-03/msg00481.html> |
| 603 | |
| 604 | =head2 Tied filehandles and write() don't mix |
| 605 | |
| 606 | There is no method on tied filehandles to allow them to be called back by |
| 607 | formats. |
| 608 | |
| 609 | =head2 Attach/detach debugger from running program |
| 610 | |
| 611 | The old perltodo notes "With C<gdb>, you can attach the debugger to a running |
| 612 | program if you pass the process ID. It would be good to do this with the Perl |
| 613 | debugger on a running Perl program, although I'm not sure how it would be |
| 614 | done." ssh and screen do this with named pipes in /tmp. Maybe we can too. |
| 615 | |
| 616 | =head2 Optimize away empty destructors |
| 617 | |
| 618 | Defining an empty DESTROY method might be useful (notably in |
| 619 | AUTOLOAD-enabled classes), but it's still a bit expensive to call. That |
| 620 | could probably be optimized. |
| 621 | |
| 622 | =head2 LVALUE functions for lists |
| 623 | |
| 624 | The old perltodo notes that lvalue functions don't work for list or hash |
| 625 | slices. This would be good to fix. |
| 626 | |
| 627 | =head2 LVALUE functions in the debugger |
| 628 | |
| 629 | The old perltodo notes that lvalue functions don't work in the debugger. This |
| 630 | would be good to fix. |
| 631 | |
| 632 | =head2 regexp optimiser optional |
| 633 | |
| 634 | The regexp optimiser is not optional. It should configurable to be, to allow |
| 635 | its performance to be measured, and its bugs to be easily demonstrated. |
| 636 | |
| 637 | =head2 delete &function |
| 638 | |
| 639 | Allow to delete functions. One can already undef them, but they're still |
| 640 | in the stash. |
| 641 | |
| 642 | =head2 C</w> regex modifier |
| 643 | |
| 644 | That flag would enable to match whole words, and also to interpolate |
| 645 | arrays as alternations. With it, C</P/w> would be roughly equivalent to: |
| 646 | |
| 647 | do { local $"='|'; /\b(?:P)\b/ } |
| 648 | |
| 649 | See L<http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/2007-01/msg00400.html> |
| 650 | for the discussion. |
| 651 | |
| 652 | =head2 optional optimizer |
| 653 | |
| 654 | Make the peephole optimizer optional. Currently it performs two tasks as |
| 655 | it walks the optree - genuine peephole optimisations, and necessary fixups of |
| 656 | ops. It would be good to find an efficient way to switch out the |
| 657 | optimisations whilst keeping the fixups. |
| 658 | |
| 659 | =head2 You WANT *how* many |
| 660 | |
| 661 | Currently contexts are void, scalar and list. split has a special mechanism in |
| 662 | place to pass in the number of return values wanted. It would be useful to |
| 663 | have a general mechanism for this, backwards compatible and little speed hit. |
| 664 | This would allow proposals such as short circuiting sort to be implemented |
| 665 | as a module on CPAN. |
| 666 | |
| 667 | =head2 lexical aliases |
| 668 | |
| 669 | Allow lexical aliases (maybe via the syntax C<my \$alias = \$foo>. |
| 670 | |
| 671 | =head2 entersub XS vs Perl |
| 672 | |
| 673 | At the moment pp_entersub is huge, and has code to deal with entering both |
| 674 | perl and XS subroutines. Subroutine implementations rarely change between |
| 675 | perl and XS at run time, so investigate using 2 ops to enter subs (one for |
| 676 | XS, one for perl) and swap between if a sub is redefined. |
| 677 | |
| 678 | =head2 Self ties |
| 679 | |
| 680 | self ties are currently illegal because they caused too many segfaults. Maybe |
| 681 | the causes of these could be tracked down and self-ties on all types re- |
| 682 | instated. |
| 683 | |
| 684 | =head2 Optimize away @_ |
| 685 | |
| 686 | The old perltodo notes "Look at the "reification" code in C<av.c>". |
| 687 | |
| 688 | =head2 Properly Unicode safe tokeniser and pads. |
| 689 | |
| 690 | The tokeniser isn't actually very UTF-8 clean. C<use utf8;> is a hack - |
| 691 | variable names are stored in stashes as raw bytes, without the utf-8 flag |
| 692 | set. The pad API only takes a C<char *> pointer, so that's all bytes too. The |
| 693 | tokeniser ignores the UTF-8-ness of C<PL_rsfp>, or any SVs returned from |
| 694 | source filters. All this could be fixed. |
| 695 | |
| 696 | =head2 The yada yada yada operators |
| 697 | |
| 698 | Perl 6's Synopsis 3 says: |
| 699 | |
| 700 | I<The ... operator is the "yada, yada, yada" list operator, which is used as |
| 701 | the body in function prototypes. It complains bitterly (by calling fail) |
| 702 | if it is ever executed. Variant ??? calls warn, and !!! calls die.> |
| 703 | |
| 704 | Those would be nice to add to Perl 5. That could be done without new ops. |
| 705 | |
| 706 | =head2 Virtualize operating system access |
| 707 | |
| 708 | Implement a set of "vtables" that virtualizes operating system access |
| 709 | (open(), mkdir(), unlink(), readdir(), getenv(), etc.) At the very |
| 710 | least these interfaces should take SVs as "name" arguments instead of |
| 711 | bare char pointers; probably the most flexible and extensible way |
| 712 | would be for the Perl-facing interfaces to accept HVs. The system |
| 713 | needs to be per-operating-system and per-file-system |
| 714 | hookable/filterable, preferably both from XS and Perl level |
| 715 | (L<perlport/"Files and Filesystems"> is good reading at this point, |
| 716 | in fact, all of L<perlport> is.) |
| 717 | |
| 718 | This has actually already been implemented (but only for Win32), |
| 719 | take a look at F<iperlsys.h> and F<win32/perlhost.h>. While all Win32 |
| 720 | variants go through a set of "vtables" for operating system access, |
| 721 | non-Win32 systems currently go straight for the POSIX/UNIX-style |
| 722 | system/library call. Similar system as for Win32 should be |
| 723 | implemented for all platforms. The existing Win32 implementation |
| 724 | probably does not need to survive alongside this proposed new |
| 725 | implementation, the approaches could be merged. |
| 726 | |
| 727 | What would this give us? One often-asked-for feature this would |
| 728 | enable is using Unicode for filenames, and other "names" like %ENV, |
| 729 | usernames, hostnames, and so forth. |
| 730 | (See L<perlunicode/"When Unicode Does Not Happen">.) |
| 731 | |
| 732 | But this kind of virtualization would also allow for things like |
| 733 | virtual filesystems, virtual networks, and "sandboxes" (though as long |
| 734 | as dynamic loading of random object code is allowed, not very safe |
| 735 | sandboxes since external code of course know not of Perl's vtables). |
| 736 | An example of a smaller "sandbox" is that this feature can be used to |
| 737 | implement per-thread working directories: Win32 already does this. |
| 738 | |
| 739 | See also L</"Extend PerlIO and PerlIO::Scalar">. |
| 740 | |
| 741 | =head1 Big projects |
| 742 | |
| 743 | Tasks that will get your name mentioned in the description of the "Highlights |
| 744 | of 5.12" |
| 745 | |
| 746 | =head2 make ithreads more robust |
| 747 | |
| 748 | Generally make ithreads more robust. See also L</iCOW> |
| 749 | |
| 750 | This task is incremental - even a little bit of work on it will help, and |
| 751 | will be greatly appreciated. |
| 752 | |
| 753 | One bit would be to write the missing code in sv.c:Perl_dirp_dup. |
| 754 | |
| 755 | Fix Perl_sv_dup, et al so that threads can return objects. |
| 756 | |
| 757 | =head2 iCOW |
| 758 | |
| 759 | Sarathy and Arthur have a proposal for an improved Copy On Write which |
| 760 | specifically will be able to COW new ithreads. If this can be implemented |
| 761 | it would be a good thing. |
| 762 | |
| 763 | =head2 (?{...}) closures in regexps |
| 764 | |
| 765 | Fix (or rewrite) the implementation of the C</(?{...})/> closures. |
| 766 | |
| 767 | =head2 A re-entrant regexp engine |
| 768 | |
| 769 | This will allow the use of a regex from inside (?{ }), (??{ }) and |
| 770 | (?(?{ })|) constructs. |
| 771 | |
| 772 | =head2 Add class set operations to regexp engine |
| 773 | |
| 774 | Apparently these are quite useful. Anyway, Jeffery Friedl wants them. |
| 775 | |
| 776 | demerphq has this on his todo list, but right at the bottom. |