3 perltodo - Perl TO-DO List
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.
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:
16 http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/
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?
23 =head1 Tasks that only need Perl knowledge
25 =head2 Remove duplication of test setup.
27 Schwern notes, that there's duplication of code - lots and lots of tests have
28 some variation on the big block of C<$Is_Foo> checks. We can safely put this
29 into a file, change it to build an C<%Is> hash and require it. Maybe just put
30 it into F<test.pl>. Throw in the handy tainting subroutines.
32 =head2 merge common code in installperl and installman
34 There are some common subroutines and a common C<BEGIN> block in F<installperl>
35 and F<installman>. These should probably be merged. It would also be good to
36 check for duplication in all the utility scripts supplied in the source
37 tarball. It might be good to move them all to a subdirectory, but this would
38 require careful checking to find all places that call them, and change those
41 =head2 common test code for timed bail out
43 Write portable self destruct code for tests to stop them burning CPU in
44 infinite loops. This needs to avoid using alarm, as some of the tests are
45 testing alarm/sleep or timers.
47 =head2 POD -E<gt> HTML conversion in the core still sucks
49 Which is crazy given just how simple POD purports to be, and how simple HTML
50 can be. It's not actually I<as> simple as it sounds, particularly with the
51 flexibility POD allows for C<=item>, but it would be good to improve the
52 visual appeal of the HTML generated, and to avoid it having any validation
53 errors. See also L</make HTML install work>, as the layout of installation tree
54 is needed to improve the cross-linking.
56 The addition of C<Pod::Simple> and its related modules may make this task
59 =head2 merge checkpods and podchecker
61 F<pod/checkpods.PL> (and C<make check> in the F<pod/> subdirectory)
62 implements a very basic check for pod files, but the errors it discovers
63 aren't found by podchecker. Add this check to podchecker, get rid of
64 checkpods and have C<make check> use podchecker.
66 =head2 perlmodlib.PL rewrite
68 Currently perlmodlib.PL needs to be run from a source directory where perl
69 has been built, or some modules won't be found, and others will be
70 skipped. Make it run from a clean perl source tree (so it's reproducible).
72 =head2 Parallel testing
74 (This probably impacts much more than the core: also the Test::Harness
75 and TAP::* modules on CPAN.)
77 The core regression test suite is getting ever more comprehensive, which has
78 the side effect that it takes longer to run. This isn't so good. Investigate
79 whether it would be feasible to give the harness script the B<option> of
80 running sets of tests in parallel. This would be useful for tests in
81 F<t/op/*.t> and F<t/uni/*.t> and maybe some sets of tests in F<lib/>.
89 How does screen layout work when you're running more than one test?
93 How does the caller of test specify how many tests to run in parallel?
97 How do setup/teardown tests identify themselves?
101 Pugs already does parallel testing - can their approach be re-used?
103 =head2 Make Schwern poorer
105 We should have tests for everything. When all the core's modules are tested,
106 Schwern has promised to donate to $500 to TPF. We may need volunteers to
107 hold him upside down and shake vigorously in order to actually extract the
110 =head2 Improve the coverage of the core tests
112 Use Devel::Cover to ascertain the core modules's test coverage, then add
113 tests that are currently missing.
117 A full test suite for the B module would be nice.
119 =head2 Deparse inlined constants
123 use constant PI => 4;
126 will currently deparse as
128 use constant ('PI', 4);
131 because the tokenizer inlines the value of the constant subroutine C<PI>.
132 This allows various compile time optimisations, such as constant folding
133 and dead code elimination. Where these haven't happened (such as the example
134 above) it ought be possible to make B::Deparse work out the name of the
135 original constant, because just enough information survives in the symbol
136 table to do this. Specifically, the same scalar is used for the constant in
137 the optree as is used for the constant subroutine, so by iterating over all
138 symbol tables and generating a mapping of SV address to constant name, it
139 would be possible to provide B::Deparse with this functionality.
141 =head2 A decent benchmark
143 C<perlbench> seems impervious to any recent changes made to the perl core. It
144 would be useful to have a reasonable general benchmarking suite that roughly
145 represented what current perl programs do, and measurably reported whether
146 tweaks to the core improve, degrade or don't really affect performance, to
147 guide people attempting to optimise the guts of perl. Gisle would welcome
148 new tests for perlbench.
150 =head2 fix tainting bugs
152 Fix the bugs revealed by running the test suite with the C<-t> switch (via
153 C<make test.taintwarn>).
155 =head2 Dual life everything
157 As part of the "dists" plan, anything that doesn't belong in the smallest perl
158 distribution needs to be dual lifed. Anything else can be too. Figure out what
159 changes would be needed to package that module and its tests up for CPAN, and
160 do so. Test it with older perl releases, and fix the problems you find.
162 To make a minimal perl distribution, it's useful to look at
163 F<t/lib/commonsense.t>.
165 =head2 Improving C<threads::shared>
167 Investigate whether C<threads::shared> could share aggregates properly with
168 only Perl level changes to shared.pm
170 =head2 POSIX memory footprint
172 Ilya observed that use POSIX; eats memory like there's no tomorrow, and at
173 various times worked to cut it down. There is probably still fat to cut out -
174 for example POSIX passes Exporter some very memory hungry data structures.
176 =head2 embed.pl/makedef.pl
178 There is a script F<embed.pl> that generates several header files to prefix
179 all of Perl's symbols in a consistent way, to provide some semblance of
180 namespace support in C<C>. Functions are declared in F<embed.fnc>, variables
181 in F<interpvar.h>. Quite a few of the functions and variables
182 are conditionally declared there, using C<#ifdef>. However, F<embed.pl>
183 doesn't understand the C macros, so the rules about which symbols are present
184 when is duplicated in F<makedef.pl>. Writing things twice is bad, m'kay.
185 It would be good to teach C<embed.pl> to understand the conditional
186 compilation, and hence remove the duplication, and the mistakes it has caused.
188 =head2 use strict; and AutoLoad
190 Currently if you write
193 use AutoLoader 'AUTOLOAD';
198 print join (' ', No, strict, here), "!\n";
201 then C<use strict;> isn't in force within the autoloaded subroutines. It would
202 be more consistent (and less surprising) to arrange for all lexical pragmas
203 in force at the __END__ block to be in force within each autoloaded subroutine.
205 There's a similar problem with SelfLoader.
207 =head1 Tasks that need a little sysadmin-type knowledge
209 Or if you prefer, tasks that you would learn from, and broaden your skills
212 =head2 make HTML install work
214 There is an C<installhtml> target in the Makefile. It's marked as
215 "experimental". It would be good to get this tested, make it work reliably, and
216 remove the "experimental" tag. This would include
222 Checking that cross linking between various parts of the documentation works.
223 In particular that links work between the modules (files with POD in F<lib/>)
224 and the core documentation (files in F<pod/>)
228 Work out how to split C<perlfunc> into chunks, preferably one per function
229 group, preferably with general case code that could be used elsewhere.
230 Challenges here are correctly identifying the groups of functions that go
231 together, and making the right named external cross-links point to the right
232 page. Things to be aware of are C<-X>, groups such as C<getpwnam> to
233 C<endservent>, two or more C<=items> giving the different parameter lists, such
236 =item substr EXPR,OFFSET,LENGTH,REPLACEMENT
237 =item substr EXPR,OFFSET,LENGTH
238 =item substr EXPR,OFFSET
240 and different parameter lists having different meanings. (eg C<select>)
244 =head2 compressed man pages
246 Be able to install them. This would probably need a configure test to see how
247 the system does compressed man pages (same directory/different directory?
248 same filename/different filename), as well as tweaking the F<installman> script
249 to compress as necessary.
251 =head2 Add a code coverage target to the Makefile
253 Make it easy for anyone to run Devel::Cover on the core's tests. The steps
254 to do this manually are roughly
260 do a normal C<Configure>, but include Devel::Cover as a module to install
261 (see F<INSTALL> for how to do this)
269 cd t; HARNESS_PERL_SWITCHES=-MDevel::Cover ./perl -I../lib harness
273 Process the resulting Devel::Cover database
277 This just give you the coverage of the F<.pm>s. To also get the C level
284 Additionally tell C<Configure> to use the appropriate C compiler flags for
291 (instead of C<make perl>)
295 After running the tests run C<gcov> to generate all the F<.gcov> files.
296 (Including down in the subdirectories of F<ext/>
300 (From the top level perl directory) run C<gcov2perl> on all the C<.gcov> files
301 to get their stats into the cover_db directory.
305 Then process the Devel::Cover database
309 It would be good to add a single switch to C<Configure> to specify that you
310 wanted to perform perl level coverage, and another to specify C level
311 coverage, and have C<Configure> and the F<Makefile> do all the right things
314 =head2 Make Config.pm cope with differences between built and installed perl
316 Quite often vendors ship a perl binary compiled with their (pay-for)
317 compilers. People install a free compiler, such as gcc. To work out how to
318 build extensions, Perl interrogates C<%Config>, so in this situation
319 C<%Config> describes compilers that aren't there, and extension building
320 fails. This forces people into choosing between re-compiling perl themselves
321 using the compiler they have, or only using modules that the vendor ships.
323 It would be good to find a way teach C<Config.pm> about the installation setup,
324 possibly involving probing at install time or later, so that the C<%Config> in
325 a binary distribution better describes the installed machine, when the
326 installed machine differs from the build machine in some significant way.
328 =head2 linker specification files
330 Some platforms mandate that you provide a list of a shared library's external
331 symbols to the linker, so the core already has the infrastructure in place to
332 do this for generating shared perl libraries. My understanding is that the
333 GNU toolchain can accept an optional linker specification file, and restrict
334 visibility just to symbols declared in that file. It would be good to extend
335 F<makedef.pl> to support this format, and to provide a means within
336 C<Configure> to enable it. This would allow Unix users to test that the
337 export list is correct, and to build a perl that does not pollute the global
338 namespace with private symbols.
340 =head2 Cross-compile support
342 Currently C<Configure> understands C<-Dusecrosscompile> option. This option
343 arranges for building C<miniperl> for TARGET machine, so this C<miniperl> is
344 assumed then to be copied to TARGET machine and used as a replacement of full
347 This could be done little differently. Namely C<miniperl> should be built for
348 HOST and then full C<perl> with extensions should be compiled for TARGET.
349 This, however, might require extra trickery for %Config: we have one config
350 first for HOST and then another for TARGET. Tools like MakeMaker will be
351 mightily confused. Having around two different types of executables and
352 libraries (HOST and TARGET) makes life interesting for Makefiles and
353 shell (and Perl) scripts. There is $Config{run}, normally empty, which
354 can be used as an execution wrapper. Also note that in some
355 cross-compilation/execution environments the HOST and the TARGET do
356 not see the same filesystem(s), the $Config{run} may need to do some
357 file/directory copying back and forth.
361 Make F<pod/roffitall> be updated by F<pod/buildtoc>.
363 =head1 Tasks that need a little C knowledge
365 These tasks would need a little C knowledge, but don't need any specific
366 background or experience with XS, or how the Perl interpreter works
368 =head2 Weed out needless PERL_UNUSED_ARG
370 The C code uses the macro C<PERL_UNUSED_ARG> to stop compilers warning about
371 unused arguments. Often the arguments can't be removed, as there is an
372 external constraint that determines the prototype of the function, so this
373 approach is valid. However, there are some cases where C<PERL_UNUSED_ARG>
374 could be removed. Specifically
380 The prototypes of (nearly all) static functions can be changed
384 Unused arguments generated by short cut macros are wasteful - the short cut
385 macro used can be changed.
391 C<Perl_ck_lengthconst> does nothing, but has the comment
393 /* XXX length optimization goes here */
395 It predates 5.003. Investigate what it's about, and then implement it.
397 =head2 Modernize the order of directories in @INC
399 The way @INC is laid out by default, one cannot upgrade core (dual-life)
400 modules without overwriting files. This causes problems for binary
401 package builders. One possible proposal is laid out in this
403 L<http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/2002-04/msg02380.html>.
407 Natively 64-bit systems need neither -Duse64bitint nor -Duse64bitall.
408 On these systems, it might be the default compilation mode, and there
409 is currently no guarantee that passing no use64bitall option to the
410 Configure process will build a 32bit perl. Implementing -Duse32bit*
411 options would be nice for perl 5.12.
413 =head2 Make it clear from -v if this is the exact official release
415 Currently perl from C<p4>/C<rsync> ships with a F<patchlevel.h> file that
416 usually defines one local patch, of the form "MAINT12345" or "RC1". The output
417 of perl -v doesn't report that a perl isn't an official release, and this
418 information can get lost in bugs reports. Because of this, the minor version
419 isn't bumped up until RC time, to minimise the possibility of versions of perl
420 escaping that believe themselves to be newer than they actually are.
422 It would be useful to find an elegant way to have the "this is an interim
423 maintenance release" or "this is a release candidate" in the terse -v output,
424 and have it so that it's easy for the pumpking to remove this just as the
425 release tarball is rolled up. This way the version pulled out of rsync would
426 always say "I'm a development release" and it would be safe to bump the
427 reported minor version as soon as a release ships, which would aid perl
430 This task is really about thinking of an elegant way to arrange the C source
431 such that it's trivial for the Pumpking to flag "this is an official release"
432 when making a tarball, yet leave the default source saying "I'm not the
435 =head2 Profile Perl - am I hot or not?
437 The Perl source code is stable enough that it makes sense to profile it,
438 identify and optimise the hotspots. It would be good to measure the
439 performance of the Perl interpreter using free tools such as cachegrind,
440 gprof, and dtrace, and work to reduce the bottlenecks they reveal.
442 As part of this, the idea of F<pp_hot.c> is that it contains the I<hot> ops,
443 the ops that are most commonly used. The idea is that by grouping them, their
444 object code will be adjacent in the executable, so they have a greater chance
445 of already being in the CPU cache (or swapped in) due to being near another op
448 Except that it's not clear if these really are the most commonly used ops. So
449 as part of exercising your skills with coverage and profiling tools you might
450 want to determine what ops I<really> are the most commonly used. And in turn
451 suggest evictions and promotions to achieve a better F<pp_hot.c>.
453 =head2 Allocate OPs from arenas
455 Currently all new OP structures are individually malloc()ed and free()d.
456 All C<malloc> implementations have space overheads, and are now as fast as
457 custom allocates so it would both use less memory and less CPU to allocate
458 the various OP structures from arenas. The SV arena code can probably be
461 Note that Configuring perl with C<-Accflags=-DPL_OP_SLAB_ALLOC> will use
462 Perl_Slab_alloc() to pack optrees into a contiguous block, which is
463 probably superior to the use of OP arenas, esp. from a cache locality
464 standpoint. See L<Profile Perl - am I hot or not?>.
466 =head2 Improve win32/wince.c
468 Currently, numerous functions look virtually, if not completely,
469 identical in both C<win32/wince.c> and C<win32/win32.c> files, which can't
472 =head2 Use secure CRT functions when building with VC8 on Win32
474 Visual C++ 2005 (VC++ 8.x) deprecated a number of CRT functions on the basis
475 that they were "unsafe" and introduced differently named secure versions of
476 them as replacements, e.g. instead of writing
478 FILE* f = fopen(__FILE__, "r");
483 errno_t err = fopen_s(&f, __FILE__, "r");
485 Currently, the warnings about these deprecations have been disabled by adding
486 -D_CRT_SECURE_NO_DEPRECATE to the CFLAGS. It would be nice to remove that
487 warning suppressant and actually make use of the new secure CRT functions.
489 There is also a similar issue with POSIX CRT function names like fileno having
490 been deprecated in favour of ISO C++ conformant names like _fileno. These
491 warnings are also currently suppressed by adding -D_CRT_NONSTDC_NO_DEPRECATE. It
492 might be nice to do as Microsoft suggest here too, although, unlike the secure
493 functions issue, there is presumably little or no benefit in this case.
495 =head2 strcat(), strcpy(), strncat(), strncpy(), sprintf(), vsprintf()
497 Maybe create a utility that checks after each libperl.a creation that
498 none of the above (nor sprintf(), vsprintf(), or *SHUDDER* gets())
499 ever creep back to libperl.a.
501 nm libperl.a | ./miniperl -alne '$o = $F[0] if /:$/; print "$o $F[1]" if $F[0] eq "U" && $F[1] =~ /^(?:strn?c(?:at|py)|v?sprintf|gets)$/'
503 Note, of course, that this will only tell whether B<your> platform
504 is using those naughty interfaces.
506 =head2 -D_FORTIFY_SOURCE=2, -fstack-protector
508 Recent glibcs support C<-D_FORTIFY_SOURCE=2> and recent gcc
509 (4.1 onwards?) supports C<-fstack-protector>, both of which give
510 protection against various kinds of buffer overflow problems.
511 These should probably be used for compiling Perl whenever available,
512 Configure and/or hints files should be adjusted to probe for the
513 availability of these features and enable them as appropriate.
515 =head1 Tasks that need a knowledge of XS
517 These tasks would need C knowledge, and roughly the level of knowledge of
518 the perl API that comes from writing modules that use XS to interface to
521 =head2 autovivification
523 Make all autovivification consistent w.r.t LVALUE/RVALUE and strict/no strict;
525 This task is incremental - even a little bit of work on it will help.
527 =head2 Unicode in Filenames
529 chdir, chmod, chown, chroot, exec, glob, link, lstat, mkdir, open,
530 opendir, qx, readdir, readlink, rename, rmdir, stat, symlink, sysopen,
531 system, truncate, unlink, utime, -X. All these could potentially accept
532 Unicode filenames either as input or output (and in the case of system
533 and qx Unicode in general, as input or output to/from the shell).
534 Whether a filesystem - an operating system pair understands Unicode in
537 Known combinations that have some level of understanding include
538 Microsoft NTFS, Apple HFS+ (In Mac OS 9 and X) and Apple UFS (in Mac
539 OS X), NFS v4 is rumored to be Unicode, and of course Plan 9. How to
540 create Unicode filenames, what forms of Unicode are accepted and used
541 (UCS-2, UTF-16, UTF-8), what (if any) is the normalization form used,
542 and so on, varies. Finding the right level of interfacing to Perl
543 requires some thought. Remember that an OS does not implicate a
546 (The Windows -C command flag "wide API support" has been at least
547 temporarily retired in 5.8.1, and the -C has been repurposed, see
550 Most probably the right way to do this would be this:
551 L</"Virtualize operating system access">.
553 =head2 Unicode in %ENV
555 Currently the %ENV entries are always byte strings.
556 See L</"Virtualize operating system access">.
558 =head2 Unicode and glob()
560 Currently glob patterns and filenames returned from File::Glob::glob()
561 are always byte strings. See L</"Virtualize operating system access">.
563 =head2 Unicode and lc/uc operators
565 Some built-in operators (C<lc>, C<uc>, etc.) behave differently, based on
566 what the internal encoding of their argument is. That should not be the
567 case. Maybe add a pragma to switch behaviour.
569 =head2 use less 'memory'
571 Investigate trade offs to switch out perl's choices on memory usage.
572 Particularly perl should be able to give memory back.
574 This task is incremental - even a little bit of work on it will help.
576 =head2 Re-implement C<:unique> in a way that is actually thread-safe
578 The old implementation made bad assumptions on several levels. A good 90%
579 solution might be just to make C<:unique> work to share the string buffer
580 of SvPVs. That way large constant strings can be shared between ithreads,
581 such as the configuration information in F<Config>.
583 =head2 Make tainting consistent
585 Tainting would be easier to use if it didn't take documented shortcuts and
586 allow taint to "leak" everywhere within an expression.
588 =head2 readpipe(LIST)
590 system() accepts a LIST syntax (and a PROGRAM LIST syntax) to avoid
591 running a shell. readpipe() (the function behind qx//) could be similarly
594 =head2 Audit the code for destruction ordering assumptions
598 /* Need to check SvMAGICAL, as during global destruction it may be that
599 AvARYLEN(av) has been freed before av, and hence the SvANY() pointer
600 is now part of the linked list of SV heads, rather than pointing to
601 the original body. */
602 /* FIXME - audit the code for other bugs like this one. */
604 adding the C<SvMAGICAL> check to
606 if (AvARYLEN(av) && SvMAGICAL(AvARYLEN(av))) {
607 MAGIC *mg = mg_find (AvARYLEN(av), PERL_MAGIC_arylen);
609 Go through the core and look for similar assumptions that SVs have particular
610 types, as all bets are off during global destruction.
612 =head2 Extend PerlIO and PerlIO::Scalar
614 PerlIO::Scalar doesn't know how to truncate(). Implementing this
615 would require extending the PerlIO vtable.
617 Similarly the PerlIO vtable doesn't know about formats (write()), or
618 about stat(), or chmod()/chown(), utime(), or flock().
620 (For PerlIO::Scalar it's hard to see what e.g. mode bits or ownership
623 PerlIO doesn't do directories or symlinks, either: mkdir(), rmdir(),
624 opendir(), closedir(), seekdir(), rewinddir(), glob(); symlink(),
627 See also L</"Virtualize operating system access">.
629 =head2 -C on the #! line
631 It should be possible to make -C work correctly if found on the #! line,
632 given that all perl command line options are strict ASCII, and -C changes
633 only the interpretation of non-ASCII characters, and not for the script file
634 handle. To make it work needs some investigation of the ordering of function
635 calls during startup, and (by implication) a bit of tweaking of that order.
637 =head2 Propagate const outwards from Perl_moreswitches()
639 Change 32057 changed the parameter and return value of C<Perl_moreswitches()>
640 from <char *> to <const char *>. It should now be possible to propagate
641 const-correctness outwards to C<S_parse_body()>, C<Perl_moreswitches()>
644 =head2 Duplicate logic in S_method_common() and Perl_gv_fetchmethod_autoload()
646 A comment in C<S_method_common> notes
648 /* This code tries to figure out just what went wrong with
649 gv_fetchmethod. It therefore needs to duplicate a lot of
650 the internals of that function. We can't move it inside
651 Perl_gv_fetchmethod_autoload(), however, since that would
652 cause UNIVERSAL->can("NoSuchPackage::foo") to croak, and we
656 If C<Perl_gv_fetchmethod_autoload> gets rewritten to take (more) flag bits,
657 then it ought to be possible to move the logic from C<S_method_common> to
658 the "right" place. When making this change it would probably be good to also
659 pass in at least the method name length, if not also pre-computed hash values
660 when known. (I'm contemplating a plan to pre-compute hash values for common
661 fixed strings such as C<ISA> and pass them in to functions.)
663 =head2 Organize error messages
665 Perl's diagnostics (error messages, see L<perldiag>) could use
666 reorganizing and formalizing so that each error message has its
667 stable-for-all-eternity unique id, categorized by severity, type, and
668 subsystem. (The error messages would be listed in a datafile outside
669 of the Perl source code, and the source code would only refer to the
670 messages by the id.) This clean-up and regularizing should apply
671 for all croak() messages.
673 This would enable all sorts of things: easier translation/localization
674 of the messages (though please do keep in mind the caveats of
675 L<Locale::Maketext> about too straightforward approaches to
676 translation), filtering by severity, and instead of grepping for a
677 particular error message one could look for a stable error id. (Of
678 course, changing the error messages by default would break all the
679 existing software depending on some particular error message...)
681 This kind of functionality is known as I<message catalogs>. Look for
682 inspiration for example in the catgets() system, possibly even use it
683 if available-- but B<only> if available, all platforms will B<not>
686 For the really pure at heart, consider extending this item to cover
687 also the warning messages (see L<perllexwarn>, C<warnings.pl>).
689 =head1 Tasks that need a knowledge of the interpreter
691 These tasks would need C knowledge, and knowledge of how the interpreter works,
692 or a willingness to learn.
694 =head2 lexicals used only once
698 $ perl -we '$pie = 42'
699 Name "main::pie" used only once: possible typo at -e line 1.
703 $ perl -we 'my $pie = 42'
705 Logically all lexicals used only once should warn, if the user asks for
706 warnings. An unworked RT ticket (#5087) has been open for almost seven
707 years for this discrepancy.
711 The handling of Unicode is unclean in many places. For example, the regexp
712 engine matches in Unicode semantics whenever the string or the pattern is
713 flagged as UTF-8, but that should not be dependent on an internal storage
714 detail of the string. Likewise, case folding behaviour is dependent on the
715 UTF8 internal flag being on or off.
717 =head2 Properly Unicode safe tokeniser and pads.
719 The tokeniser isn't actually very UTF-8 clean. C<use utf8;> is a hack -
720 variable names are stored in stashes as raw bytes, without the utf-8 flag
721 set. The pad API only takes a C<char *> pointer, so that's all bytes too. The
722 tokeniser ignores the UTF-8-ness of C<PL_rsfp>, or any SVs returned from
723 source filters. All this could be fixed.
725 =head2 state variable initialization in list context
727 Currently this is illegal:
729 state ($a, $b) = foo();
731 In Perl 6, C<state ($a) = foo();> and C<(state $a) = foo();> have different
732 semantics, which is tricky to implement in Perl 5 as currently they produce
733 the same opcode trees. The Perl 6 design is firm, so it would be good to
734 implement the necessary code in Perl 5. There are comments in
735 C<Perl_newASSIGNOP()> that show the code paths taken by various assignment
736 constructions involving state variables.
738 =head2 Implement $value ~~ 0 .. $range
740 It would be nice to extend the syntax of the C<~~> operator to also
741 understand numeric (and maybe alphanumeric) ranges.
743 =head2 A does() built-in
745 Like ref(), only useful. It would call the C<DOES> method on objects; it
746 would also tell whether something can be dereferenced as an
747 array/hash/etc., or used as a regexp, etc.
748 L<http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/2007-03/msg00481.html>
750 =head2 Tied filehandles and write() don't mix
752 There is no method on tied filehandles to allow them to be called back by
755 =head2 Attach/detach debugger from running program
757 The old perltodo notes "With C<gdb>, you can attach the debugger to a running
758 program if you pass the process ID. It would be good to do this with the Perl
759 debugger on a running Perl program, although I'm not sure how it would be
760 done." ssh and screen do this with named pipes in /tmp. Maybe we can too.
762 =head2 Optimize away empty destructors
764 Defining an empty DESTROY method might be useful (notably in
765 AUTOLOAD-enabled classes), but it's still a bit expensive to call. That
766 could probably be optimized.
768 =head2 LVALUE functions for lists
770 The old perltodo notes that lvalue functions don't work for list or hash
771 slices. This would be good to fix.
773 =head2 LVALUE functions in the debugger
775 The old perltodo notes that lvalue functions don't work in the debugger. This
776 would be good to fix.
778 =head2 regexp optimiser optional
780 The regexp optimiser is not optional. It should configurable to be, to allow
781 its performance to be measured, and its bugs to be easily demonstrated.
783 =head2 delete &function
785 Allow to delete functions. One can already undef them, but they're still
788 =head2 C</w> regex modifier
790 That flag would enable to match whole words, and also to interpolate
791 arrays as alternations. With it, C</P/w> would be roughly equivalent to:
793 do { local $"='|'; /\b(?:P)\b/ }
795 See L<http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/2007-01/msg00400.html>
798 =head2 optional optimizer
800 Make the peephole optimizer optional. Currently it performs two tasks as
801 it walks the optree - genuine peephole optimisations, and necessary fixups of
802 ops. It would be good to find an efficient way to switch out the
803 optimisations whilst keeping the fixups.
805 =head2 You WANT *how* many
807 Currently contexts are void, scalar and list. split has a special mechanism in
808 place to pass in the number of return values wanted. It would be useful to
809 have a general mechanism for this, backwards compatible and little speed hit.
810 This would allow proposals such as short circuiting sort to be implemented
813 =head2 lexical aliases
815 Allow lexical aliases (maybe via the syntax C<my \$alias = \$foo>.
817 =head2 entersub XS vs Perl
819 At the moment pp_entersub is huge, and has code to deal with entering both
820 perl and XS subroutines. Subroutine implementations rarely change between
821 perl and XS at run time, so investigate using 2 ops to enter subs (one for
822 XS, one for perl) and swap between if a sub is redefined.
826 Self-ties are currently illegal because they caused too many segfaults. Maybe
827 the causes of these could be tracked down and self-ties on all types
830 =head2 Optimize away @_
832 The old perltodo notes "Look at the "reification" code in C<av.c>".
834 =head2 The yada yada yada operators
836 Perl 6's Synopsis 3 says:
838 I<The ... operator is the "yada, yada, yada" list operator, which is used as
839 the body in function prototypes. It complains bitterly (by calling fail)
840 if it is ever executed. Variant ??? calls warn, and !!! calls die.>
842 Those would be nice to add to Perl 5. That could be done without new ops.
844 =head2 Virtualize operating system access
846 Implement a set of "vtables" that virtualizes operating system access
847 (open(), mkdir(), unlink(), readdir(), getenv(), etc.) At the very
848 least these interfaces should take SVs as "name" arguments instead of
849 bare char pointers; probably the most flexible and extensible way
850 would be for the Perl-facing interfaces to accept HVs. The system
851 needs to be per-operating-system and per-file-system
852 hookable/filterable, preferably both from XS and Perl level
853 (L<perlport/"Files and Filesystems"> is good reading at this point,
854 in fact, all of L<perlport> is.)
856 This has actually already been implemented (but only for Win32),
857 take a look at F<iperlsys.h> and F<win32/perlhost.h>. While all Win32
858 variants go through a set of "vtables" for operating system access,
859 non-Win32 systems currently go straight for the POSIX/UNIX-style
860 system/library call. Similar system as for Win32 should be
861 implemented for all platforms. The existing Win32 implementation
862 probably does not need to survive alongside this proposed new
863 implementation, the approaches could be merged.
865 What would this give us? One often-asked-for feature this would
866 enable is using Unicode for filenames, and other "names" like %ENV,
867 usernames, hostnames, and so forth.
868 (See L<perlunicode/"When Unicode Does Not Happen">.)
870 But this kind of virtualization would also allow for things like
871 virtual filesystems, virtual networks, and "sandboxes" (though as long
872 as dynamic loading of random object code is allowed, not very safe
873 sandboxes since external code of course know not of Perl's vtables).
874 An example of a smaller "sandbox" is that this feature can be used to
875 implement per-thread working directories: Win32 already does this.
877 See also L</"Extend PerlIO and PerlIO::Scalar">.
879 =head2 Investigate PADTMP hash pessimisation
881 The peephole optimier converts constants used for hash key lookups to shared
882 hash key scalars. Under ithreads, something is undoing this work. See
883 See http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/2007-09/msg00793.html
887 Tasks that will get your name mentioned in the description of the "Highlights
890 =head2 make ithreads more robust
892 Generally make ithreads more robust. See also L</iCOW>
894 This task is incremental - even a little bit of work on it will help, and
895 will be greatly appreciated.
897 One bit would be to write the missing code in sv.c:Perl_dirp_dup.
899 Fix Perl_sv_dup, et al so that threads can return objects.
903 Sarathy and Arthur have a proposal for an improved Copy On Write which
904 specifically will be able to COW new ithreads. If this can be implemented
905 it would be a good thing.
907 =head2 (?{...}) closures in regexps
909 Fix (or rewrite) the implementation of the C</(?{...})/> closures.
911 =head2 A re-entrant regexp engine
913 This will allow the use of a regex from inside (?{ }), (??{ }) and
914 (?(?{ })|) constructs.
916 =head2 Add class set operations to regexp engine
918 Apparently these are quite useful. Anyway, Jeffery Friedl wants them.
920 demerphq has this on his todo list, but right at the bottom.