This is a live mirror of the Perl 5 development currently hosted at https://github.com/perl/perl5
Refactor test code to remove duplication is a TODO.
[perl5.git] / pod / perltodo.pod
CommitLineData
7711098a
GS
1=head1 NAME
2
3perltodo - Perl TO-DO List
4
5=head1 DESCRIPTION
e50bb9a1 6
0bdfc961
NC
7This is a list of wishes for Perl. The tasks we think are smaller or easier
8are listed first. Anyone is welcome to work on any of these, but it's a good
9idea to first contact I<perl5-porters@perl.org> to avoid duplication of
10effort. By all means contact a pumpking privately first if you prefer.
e50bb9a1 11
0bdfc961
NC
12Whilst patches to make the list shorter are most welcome, ideas to add to
13the list are also encouraged. Check the perl5-porters archives for past
14ideas, and any discussion about them. One set of archives may be found at:
e50bb9a1 15
0bdfc961 16 http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/
938c8732 17
617eabfa
NC
18What can we offer you in return? Fame, fortune, and everlasting glory? Maybe
19not, but if your patch is incorporated, then we'll add your name to the
20F<AUTHORS> file, which ships in the official distribution. How many other
21programming languages offer you 1 line of immortality?
938c8732 22
0bdfc961 23=head1 Tasks that only need Perl knowledge
e50bb9a1 24
5a176cbc
NC
25=head2 Remove duplication of test setup.
26
27Schwern notes, that there's duplication of code - lots and lots of tests have
28some variation on the big block of C<$Is_Foo> checks. We can safely put this
29into a file, change it to build an C<%Is> hash and require it. Maybe just put
30it into F<test.pl>. Throw in the handy tainting subroutines.
31
412f19a0
NC
32=head2 merge common code in installperl and installman
33
34There are some common subroutines and a common C<BEGIN> block in F<installperl>
35and F<installman>. These should probably be merged. It would also be good to
36check for duplication in all the utility scripts supplied in the source
37tarball. It might be good to move them all to a subdirectory, but this would
38require careful checking to find all places that call them, and change those
39correctly.
40
0bdfc961 41=head2 common test code for timed bail out
e50bb9a1 42
0bdfc961
NC
43Write portable self destruct code for tests to stop them burning CPU in
44infinite loops. This needs to avoid using alarm, as some of the tests are
45testing alarm/sleep or timers.
e50bb9a1 46
87a942b1 47=head2 POD -E<gt> HTML conversion in the core still sucks
e50bb9a1 48
938c8732 49Which is crazy given just how simple POD purports to be, and how simple HTML
adebf063
NC
50can be. It's not actually I<as> simple as it sounds, particularly with the
51flexibility POD allows for C<=item>, but it would be good to improve the
52visual appeal of the HTML generated, and to avoid it having any validation
53errors. See also L</make HTML install work>, as the layout of installation tree
54is needed to improve the cross-linking.
938c8732 55
dc0fb092
SP
56The addition of C<Pod::Simple> and its related modules may make this task
57easier to complete.
58
8537f021
RGS
59=head2 merge checkpods and podchecker
60
61F<pod/checkpods.PL> (and C<make check> in the F<pod/> subdirectory)
62implements a very basic check for pod files, but the errors it discovers
63aren't found by podchecker. Add this check to podchecker, get rid of
64checkpods and have C<make check> use podchecker.
65
b032e2ff
RGS
66=head2 perlmodlib.PL rewrite
67
68Currently perlmodlib.PL needs to be run from a source directory where perl
69has been built, or some modules won't be found, and others will be
70skipped. Make it run from a clean perl source tree (so it's reproducible).
71
aa237293
NC
72=head2 Parallel testing
73
b2e2905c 74(This probably impacts much more than the core: also the Test::Harness
02f21748
RGS
75and TAP::* modules on CPAN.)
76
aa237293
NC
77The core regression test suite is getting ever more comprehensive, which has
78the side effect that it takes longer to run. This isn't so good. Investigate
79whether it would be feasible to give the harness script the B<option> of
80running sets of tests in parallel. This would be useful for tests in
81F<t/op/*.t> and F<t/uni/*.t> and maybe some sets of tests in F<lib/>.
82
83Questions to answer
84
85=over 4
86
87=item 1
88
89How does screen layout work when you're running more than one test?
90
91=item 2
92
93How does the caller of test specify how many tests to run in parallel?
94
95=item 3
96
97How do setup/teardown tests identify themselves?
98
99=back
100
101Pugs already does parallel testing - can their approach be re-used?
102
0bdfc961 103=head2 Make Schwern poorer
e50bb9a1 104
613bd4f7 105We should have tests for everything. When all the core's modules are tested,
0bdfc961
NC
106Schwern has promised to donate to $500 to TPF. We may need volunteers to
107hold him upside down and shake vigorously in order to actually extract the
108cash.
3958b146 109
0bdfc961 110=head2 Improve the coverage of the core tests
e50bb9a1 111
02f21748
RGS
112Use Devel::Cover to ascertain the core modules's test coverage, then add
113tests that are currently missing.
30222c0f 114
0bdfc961 115=head2 test B
e50bb9a1 116
0bdfc961 117A full test suite for the B module would be nice.
e50bb9a1 118
636e63cb
NC
119=head2 Deparse inlined constants
120
121Code such as this
122
123 use constant PI => 4;
124 warn PI
125
126will currently deparse as
127
128 use constant ('PI', 4);
129 warn 4;
130
131because the tokenizer inlines the value of the constant subroutine C<PI>.
132This allows various compile time optimisations, such as constant folding
133and dead code elimination. Where these haven't happened (such as the example
134above) it ought be possible to make B::Deparse work out the name of the
135original constant, because just enough information survives in the symbol
136table to do this. Specifically, the same scalar is used for the constant in
137the optree as is used for the constant subroutine, so by iterating over all
138symbol tables and generating a mapping of SV address to constant name, it
139would be possible to provide B::Deparse with this functionality.
140
0bdfc961 141=head2 A decent benchmark
e50bb9a1 142
617eabfa 143C<perlbench> seems impervious to any recent changes made to the perl core. It
0bdfc961
NC
144would be useful to have a reasonable general benchmarking suite that roughly
145represented what current perl programs do, and measurably reported whether
146tweaks to the core improve, degrade or don't really affect performance, to
147guide people attempting to optimise the guts of perl. Gisle would welcome
148new tests for perlbench.
6168cf99 149
0bdfc961 150=head2 fix tainting bugs
6168cf99 151
0bdfc961
NC
152Fix the bugs revealed by running the test suite with the C<-t> switch (via
153C<make test.taintwarn>).
e50bb9a1 154
0bdfc961 155=head2 Dual life everything
e50bb9a1 156
0bdfc961
NC
157As part of the "dists" plan, anything that doesn't belong in the smallest perl
158distribution needs to be dual lifed. Anything else can be too. Figure out what
159changes would be needed to package that module and its tests up for CPAN, and
160do so. Test it with older perl releases, and fix the problems you find.
e50bb9a1 161
a393eb28
RGS
162To make a minimal perl distribution, it's useful to look at
163F<t/lib/commonsense.t>.
164
0bdfc961 165=head2 Improving C<threads::shared>
722d2a37 166
0bdfc961
NC
167Investigate whether C<threads::shared> could share aggregates properly with
168only Perl level changes to shared.pm
722d2a37 169
0bdfc961 170=head2 POSIX memory footprint
e50bb9a1 171
0bdfc961
NC
172Ilya observed that use POSIX; eats memory like there's no tomorrow, and at
173various times worked to cut it down. There is probably still fat to cut out -
174for example POSIX passes Exporter some very memory hungry data structures.
e50bb9a1 175
eed36644
NC
176=head2 embed.pl/makedef.pl
177
178There is a script F<embed.pl> that generates several header files to prefix
179all of Perl's symbols in a consistent way, to provide some semblance of
180namespace support in C<C>. Functions are declared in F<embed.fnc>, variables
907b3e23 181in F<interpvar.h>. Quite a few of the functions and variables
eed36644
NC
182are conditionally declared there, using C<#ifdef>. However, F<embed.pl>
183doesn't understand the C macros, so the rules about which symbols are present
184when is duplicated in F<makedef.pl>. Writing things twice is bad, m'kay.
185It would be good to teach C<embed.pl> to understand the conditional
186compilation, and hence remove the duplication, and the mistakes it has caused.
e50bb9a1 187
801de10e
NC
188=head2 use strict; and AutoLoad
189
190Currently if you write
191
192 package Whack;
193 use AutoLoader 'AUTOLOAD';
194 use strict;
195 1;
196 __END__
197 sub bloop {
198 print join (' ', No, strict, here), "!\n";
199 }
200
201then C<use strict;> isn't in force within the autoloaded subroutines. It would
202be more consistent (and less surprising) to arrange for all lexical pragmas
203in force at the __END__ block to be in force within each autoloaded subroutine.
204
773b3597
RGS
205There's a similar problem with SelfLoader.
206
0bdfc961 207=head1 Tasks that need a little sysadmin-type knowledge
e50bb9a1 208
0bdfc961
NC
209Or if you prefer, tasks that you would learn from, and broaden your skills
210base...
e50bb9a1 211
cd793d32 212=head2 make HTML install work
e50bb9a1 213
adebf063
NC
214There 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
216remove the "experimental" tag. This would include
217
218=over 4
219
220=item 1
221
222Checking that cross linking between various parts of the documentation works.
223In particular that links work between the modules (files with POD in F<lib/>)
224and the core documentation (files in F<pod/>)
225
226=item 2
227
617eabfa
NC
228Work out how to split C<perlfunc> into chunks, preferably one per function
229group, preferably with general case code that could be used elsewhere.
230Challenges here are correctly identifying the groups of functions that go
231together, and making the right named external cross-links point to the right
232page. Things to be aware of are C<-X>, groups such as C<getpwnam> to
233C<endservent>, two or more C<=items> giving the different parameter lists, such
234as
adebf063
NC
235
236 =item substr EXPR,OFFSET,LENGTH,REPLACEMENT
adebf063 237 =item substr EXPR,OFFSET,LENGTH
adebf063
NC
238 =item substr EXPR,OFFSET
239
240and different parameter lists having different meanings. (eg C<select>)
241
242=back
3a89a73c 243
0bdfc961
NC
244=head2 compressed man pages
245
246Be able to install them. This would probably need a configure test to see how
247the system does compressed man pages (same directory/different directory?
248same filename/different filename), as well as tweaking the F<installman> script
249to compress as necessary.
250
30222c0f
NC
251=head2 Add a code coverage target to the Makefile
252
253Make it easy for anyone to run Devel::Cover on the core's tests. The steps
254to do this manually are roughly
255
256=over 4
257
258=item *
259
260do a normal C<Configure>, but include Devel::Cover as a module to install
261(see F<INSTALL> for how to do this)
262
263=item *
264
265 make perl
266
267=item *
268
269 cd t; HARNESS_PERL_SWITCHES=-MDevel::Cover ./perl -I../lib harness
270
271=item *
272
273Process the resulting Devel::Cover database
274
275=back
276
277This just give you the coverage of the F<.pm>s. To also get the C level
278coverage you need to
279
280=over 4
281
282=item *
283
284Additionally tell C<Configure> to use the appropriate C compiler flags for
285C<gcov>
286
287=item *
288
289 make perl.gcov
290
291(instead of C<make perl>)
292
293=item *
294
295After running the tests run C<gcov> to generate all the F<.gcov> files.
296(Including down in the subdirectories of F<ext/>
297
298=item *
299
300(From the top level perl directory) run C<gcov2perl> on all the C<.gcov> files
301to get their stats into the cover_db directory.
302
303=item *
304
305Then process the Devel::Cover database
306
307=back
308
309It would be good to add a single switch to C<Configure> to specify that you
310wanted to perform perl level coverage, and another to specify C level
311coverage, and have C<Configure> and the F<Makefile> do all the right things
312automatically.
313
02f21748 314=head2 Make Config.pm cope with differences between built and installed perl
0bdfc961
NC
315
316Quite often vendors ship a perl binary compiled with their (pay-for)
317compilers. People install a free compiler, such as gcc. To work out how to
318build extensions, Perl interrogates C<%Config>, so in this situation
319C<%Config> describes compilers that aren't there, and extension building
320fails. This forces people into choosing between re-compiling perl themselves
321using the compiler they have, or only using modules that the vendor ships.
322
323It would be good to find a way teach C<Config.pm> about the installation setup,
324possibly involving probing at install time or later, so that the C<%Config> in
325a binary distribution better describes the installed machine, when the
326installed machine differs from the build machine in some significant way.
327
728f4ecd
NC
328=head2 linker specification files
329
330Some platforms mandate that you provide a list of a shared library's external
331symbols to the linker, so the core already has the infrastructure in place to
332do this for generating shared perl libraries. My understanding is that the
333GNU toolchain can accept an optional linker specification file, and restrict
334visibility just to symbols declared in that file. It would be good to extend
335F<makedef.pl> to support this format, and to provide a means within
336C<Configure> to enable it. This would allow Unix users to test that the
337export list is correct, and to build a perl that does not pollute the global
338namespace with private symbols.
339
a229ae3b
RGS
340=head2 Cross-compile support
341
342Currently C<Configure> understands C<-Dusecrosscompile> option. This option
343arranges for building C<miniperl> for TARGET machine, so this C<miniperl> is
344assumed then to be copied to TARGET machine and used as a replacement of full
345C<perl> executable.
346
d1307786 347This could be done little differently. Namely C<miniperl> should be built for
a229ae3b 348HOST and then full C<perl> with extensions should be compiled for TARGET.
d1307786 349This, however, might require extra trickery for %Config: we have one config
87a942b1
JH
350first for HOST and then another for TARGET. Tools like MakeMaker will be
351mightily confused. Having around two different types of executables and
352libraries (HOST and TARGET) makes life interesting for Makefiles and
353shell (and Perl) scripts. There is $Config{run}, normally empty, which
354can be used as an execution wrapper. Also note that in some
355cross-compilation/execution environments the HOST and the TARGET do
356not see the same filesystem(s), the $Config{run} may need to do some
357file/directory copying back and forth.
0bdfc961 358
8537f021
RGS
359=head2 roffitall
360
361Make F<pod/roffitall> be updated by F<pod/buildtoc>.
362
0bdfc961
NC
363=head1 Tasks that need a little C knowledge
364
365These tasks would need a little C knowledge, but don't need any specific
366background or experience with XS, or how the Perl interpreter works
367
99d50c9c
NC
368=head2 Exterminate PL_na!
369
370C<PL_na> festers still in the darkest corners of various typemap files.
371It needs to be exterminated, replaced by a local variable of type C<STRLEN>.
372
fbf638cb
RGS
373=head2 Modernize the order of directories in @INC
374
375The way @INC is laid out by default, one cannot upgrade core (dual-life)
376modules without overwriting files. This causes problems for binary
3d14fd97
AD
377package builders. One possible proposal is laid out in this
378message:
379L<http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/2002-04/msg02380.html>.
fbf638cb 380
bcbaa2d5
RGS
381=head2 -Duse32bit*
382
383Natively 64-bit systems need neither -Duse64bitint nor -Duse64bitall.
384On these systems, it might be the default compilation mode, and there
385is currently no guarantee that passing no use64bitall option to the
386Configure process will build a 32bit perl. Implementing -Duse32bit*
387options would be nice for perl 5.12.
388
0bdfc961 389=head2 Make it clear from -v if this is the exact official release
89007cb3 390
617eabfa
NC
391Currently perl from C<p4>/C<rsync> ships with a F<patchlevel.h> file that
392usually defines one local patch, of the form "MAINT12345" or "RC1". The output
393of perl -v doesn't report that a perl isn't an official release, and this
89007cb3 394information can get lost in bugs reports. Because of this, the minor version
fa11829f 395isn't bumped up until RC time, to minimise the possibility of versions of perl
89007cb3
NC
396escaping that believe themselves to be newer than they actually are.
397
398It would be useful to find an elegant way to have the "this is an interim
399maintenance release" or "this is a release candidate" in the terse -v output,
400and have it so that it's easy for the pumpking to remove this just as the
401release tarball is rolled up. This way the version pulled out of rsync would
402always say "I'm a development release" and it would be safe to bump the
403reported minor version as soon as a release ships, which would aid perl
404developers.
405
0bdfc961
NC
406This task is really about thinking of an elegant way to arrange the C source
407such that it's trivial for the Pumpking to flag "this is an official release"
408when making a tarball, yet leave the default source saying "I'm not the
409official release".
410
fee0a0f7 411=head2 Profile Perl - am I hot or not?
62403a3c 412
fee0a0f7
NC
413The Perl source code is stable enough that it makes sense to profile it,
414identify and optimise the hotspots. It would be good to measure the
415performance of the Perl interpreter using free tools such as cachegrind,
416gprof, and dtrace, and work to reduce the bottlenecks they reveal.
417
418As part of this, the idea of F<pp_hot.c> is that it contains the I<hot> ops,
419the ops that are most commonly used. The idea is that by grouping them, their
420object code will be adjacent in the executable, so they have a greater chance
421of already being in the CPU cache (or swapped in) due to being near another op
422already in use.
62403a3c
NC
423
424Except that it's not clear if these really are the most commonly used ops. So
fee0a0f7
NC
425as part of exercising your skills with coverage and profiling tools you might
426want to determine what ops I<really> are the most commonly used. And in turn
427suggest evictions and promotions to achieve a better F<pp_hot.c>.
62403a3c 428
98fed0ad
NC
429=head2 Allocate OPs from arenas
430
431Currently all new OP structures are individually malloc()ed and free()d.
432All C<malloc> implementations have space overheads, and are now as fast as
433custom allocates so it would both use less memory and less CPU to allocate
434the various OP structures from arenas. The SV arena code can probably be
435re-used for this.
436
539f2c54
JC
437Note that Configuring perl with C<-Accflags=-DPL_OP_SLAB_ALLOC> will use
438Perl_Slab_alloc() to pack optrees into a contiguous block, which is
439probably superior to the use of OP arenas, esp. from a cache locality
440standpoint. See L<Profile Perl - am I hot or not?>.
441
a229ae3b 442=head2 Improve win32/wince.c
0bdfc961 443
a229ae3b 444Currently, numerous functions look virtually, if not completely,
02f21748 445identical in both C<win32/wince.c> and C<win32/win32.c> files, which can't
6d71adcd
NC
446be good.
447
c5b31784
SH
448=head2 Use secure CRT functions when building with VC8 on Win32
449
450Visual C++ 2005 (VC++ 8.x) deprecated a number of CRT functions on the basis
451that they were "unsafe" and introduced differently named secure versions of
452them as replacements, e.g. instead of writing
453
454 FILE* f = fopen(__FILE__, "r");
455
456one should now write
457
458 FILE* f;
459 errno_t err = fopen_s(&f, __FILE__, "r");
460
461Currently, the warnings about these deprecations have been disabled by adding
462-D_CRT_SECURE_NO_DEPRECATE to the CFLAGS. It would be nice to remove that
463warning suppressant and actually make use of the new secure CRT functions.
464
465There is also a similar issue with POSIX CRT function names like fileno having
466been deprecated in favour of ISO C++ conformant names like _fileno. These
26a6faa8 467warnings are also currently suppressed by adding -D_CRT_NONSTDC_NO_DEPRECATE. It
c5b31784
SH
468might be nice to do as Microsoft suggest here too, although, unlike the secure
469functions issue, there is presumably little or no benefit in this case.
470
6b632b43
NC
471=head2 __FUNCTION__ for MSVC-pre-7.0
472
473Jarkko notes that one can things morally equivalent to C<__FUNCTION__>
474(or C<__func__>) even in MSVC-pre-7.0, contrary to popular belief.
475See L<http://www.codeproject.com/debug/extendedtrace.asp> if you feel like
476making C<PERL_MEM_LOG> more useful on Win32.
477
16815324
NC
478=head2 strcat(), strcpy(), strncat(), strncpy(), sprintf(), vsprintf()
479
480Maybe create a utility that checks after each libperl.a creation that
481none of the above (nor sprintf(), vsprintf(), or *SHUDDER* gets())
482ever creep back to libperl.a.
483
484 nm libperl.a | ./miniperl -alne '$o = $F[0] if /:$/; print "$o $F[1]" if $F[0] eq "U" && $F[1] =~ /^(?:strn?c(?:at|py)|v?sprintf|gets)$/'
485
486Note, of course, that this will only tell whether B<your> platform
487is using those naughty interfaces.
488
489
6d71adcd
NC
490=head1 Tasks that need a knowledge of XS
491
492These tasks would need C knowledge, and roughly the level of knowledge of
493the perl API that comes from writing modules that use XS to interface to
494C.
495
6d71adcd
NC
496=head2 autovivification
497
498Make all autovivification consistent w.r.t LVALUE/RVALUE and strict/no strict;
499
500This task is incremental - even a little bit of work on it will help.
501
502=head2 Unicode in Filenames
503
504chdir, chmod, chown, chroot, exec, glob, link, lstat, mkdir, open,
505opendir, qx, readdir, readlink, rename, rmdir, stat, symlink, sysopen,
506system, truncate, unlink, utime, -X. All these could potentially accept
507Unicode filenames either as input or output (and in the case of system
508and qx Unicode in general, as input or output to/from the shell).
509Whether a filesystem - an operating system pair understands Unicode in
510filenames varies.
511
512Known combinations that have some level of understanding include
513Microsoft NTFS, Apple HFS+ (In Mac OS 9 and X) and Apple UFS (in Mac
514OS X), NFS v4 is rumored to be Unicode, and of course Plan 9. How to
515create Unicode filenames, what forms of Unicode are accepted and used
516(UCS-2, UTF-16, UTF-8), what (if any) is the normalization form used,
517and so on, varies. Finding the right level of interfacing to Perl
518requires some thought. Remember that an OS does not implicate a
519filesystem.
520
521(The Windows -C command flag "wide API support" has been at least
522temporarily retired in 5.8.1, and the -C has been repurposed, see
523L<perlrun>.)
524
87a942b1
JH
525Most probably the right way to do this would be this:
526L</"Virtualize operating system access">.
527
6d71adcd
NC
528=head2 Unicode in %ENV
529
530Currently the %ENV entries are always byte strings.
87a942b1 531See L</"Virtualize operating system access">.
6d71adcd 532
1f2e7916
JD
533=head2 Unicode and glob()
534
535Currently glob patterns and filenames returned from File::Glob::glob()
87a942b1 536are always byte strings. See L</"Virtualize operating system access">.
1f2e7916 537
dbb0c492
RGS
538=head2 Unicode and lc/uc operators
539
540Some built-in operators (C<lc>, C<uc>, etc.) behave differently, based on
541what the internal encoding of their argument is. That should not be the
542case. Maybe add a pragma to switch behaviour.
543
6d71adcd
NC
544=head2 use less 'memory'
545
546Investigate trade offs to switch out perl's choices on memory usage.
547Particularly perl should be able to give memory back.
548
549This task is incremental - even a little bit of work on it will help.
550
551=head2 Re-implement C<:unique> in a way that is actually thread-safe
552
553The old implementation made bad assumptions on several levels. A good 90%
554solution might be just to make C<:unique> work to share the string buffer
555of SvPVs. That way large constant strings can be shared between ithreads,
556such as the configuration information in F<Config>.
557
558=head2 Make tainting consistent
559
560Tainting would be easier to use if it didn't take documented shortcuts and
561allow taint to "leak" everywhere within an expression.
562
563=head2 readpipe(LIST)
564
565system() accepts a LIST syntax (and a PROGRAM LIST syntax) to avoid
566running a shell. readpipe() (the function behind qx//) could be similarly
567extended.
568
6d71adcd
NC
569=head2 Audit the code for destruction ordering assumptions
570
571Change 25773 notes
572
573 /* Need to check SvMAGICAL, as during global destruction it may be that
574 AvARYLEN(av) has been freed before av, and hence the SvANY() pointer
575 is now part of the linked list of SV heads, rather than pointing to
576 the original body. */
577 /* FIXME - audit the code for other bugs like this one. */
578
579adding the C<SvMAGICAL> check to
580
581 if (AvARYLEN(av) && SvMAGICAL(AvARYLEN(av))) {
582 MAGIC *mg = mg_find (AvARYLEN(av), PERL_MAGIC_arylen);
583
584Go through the core and look for similar assumptions that SVs have particular
585types, as all bets are off during global destruction.
586
749904bf
JH
587=head2 Extend PerlIO and PerlIO::Scalar
588
589PerlIO::Scalar doesn't know how to truncate(). Implementing this
590would require extending the PerlIO vtable.
591
592Similarly the PerlIO vtable doesn't know about formats (write()), or
593about stat(), or chmod()/chown(), utime(), or flock().
594
595(For PerlIO::Scalar it's hard to see what e.g. mode bits or ownership
596would mean.)
597
598PerlIO doesn't do directories or symlinks, either: mkdir(), rmdir(),
599opendir(), closedir(), seekdir(), rewinddir(), glob(); symlink(),
600readlink().
601
94da6c29
JH
602See also L</"Virtualize operating system access">.
603
3236f110
NC
604=head2 -C on the #! line
605
606It should be possible to make -C work correctly if found on the #! line,
607given that all perl command line options are strict ASCII, and -C changes
608only the interpretation of non-ASCII characters, and not for the script file
609handle. To make it work needs some investigation of the ordering of function
610calls during startup, and (by implication) a bit of tweaking of that order.
611
81622873
NC
612=head2 Propagate const outwards from Perl_moreswitches()
613
614Change 32057 changed the parameter and return value of C<Perl_moreswitches()>
615from <char *> to <const char *>. It should now be possible to propagate
616const-correctness outwards to C<S_parse_body()>, C<Perl_moreswitches()>
617and C<Perl_yylex()>.
618
16815324
NC
619=head2 Duplicate logic in S_method_common() and Perl_gv_fetchmethod_autoload()
620
621A comment in C<S_method_common> notes
622
623 /* This code tries to figure out just what went wrong with
624 gv_fetchmethod. It therefore needs to duplicate a lot of
625 the internals of that function. We can't move it inside
626 Perl_gv_fetchmethod_autoload(), however, since that would
627 cause UNIVERSAL->can("NoSuchPackage::foo") to croak, and we
628 don't want that.
629 */
630
631If C<Perl_gv_fetchmethod_autoload> gets rewritten to take (more) flag bits,
632then it ought to be possible to move the logic from C<S_method_common> to
633the "right" place. When making this change it would probably be good to also
634pass in at least the method name length, if not also pre-computed hash values
635when known. (I'm contemplating a plan to pre-compute hash values for common
636fixed strings such as C<ISA> and pass them in to functions.)
637
d6c1e11f
JH
638=head2 Organize error messages
639
640Perl's diagnostics (error messages, see L<perldiag>) could use
641reorganizing so that each error message has its
642stable-for-all-eternity unique id, categorized by severity, type, and
643subsystem. (The error messages would be listed in a datafile outside
644of the Perl source code, and the source code would only refer the
645messages by the is.) This clean-up and regularizing should apply
646for all croak() messages.
647
648This would enable all sorts of things: easier translation/localization
649of the messages (though please do keep in mind the caveats of
650L<Locale::Maketext> about too straightforward approaches to
651translation), filtering by severity, and instead of grepping for a
652particular error message one could look for a stable error id. (Of
653course, changing the error messages by default would break all the
654existing software depending on some particular error message...)
655
656This kind of functionality is known as I<message catalogs>. Look for
657inspiration for example in the catgets() system, possibly even use it
658if available-- but B<only> if available, all platforms will B<not>
659catgets().
660
661For the really pure at heart, consider extending this item to cover
662also the warning messages (see L<perllexwarn>, C<warnings.pl>).
3236f110 663
0bdfc961 664=head1 Tasks that need a knowledge of the interpreter
3298bd4d 665
0bdfc961
NC
666These tasks would need C knowledge, and knowledge of how the interpreter works,
667or a willingness to learn.
3298bd4d 668
636e63cb
NC
669=head2 state variable initialization in list context
670
671Currently this is illegal:
672
673 state ($a, $b) = foo();
674
675The current Perl 6 design is that C<state ($a) = foo();> and
676C<(state $a) = foo();> have different semantics, which is tricky to implement
677in Perl 5 as currently the produce the same opcode trees. It would be useful
678to clarify that the Perl 6 design is firm, and then implement the necessary
679code in Perl 5. There are comments in C<Perl_newASSIGNOP()> that show the
680code paths taken by various assignment constructions involving state variables.
681
4fedb12c
RGS
682=head2 Implement $value ~~ 0 .. $range
683
684It would be nice to extend the syntax of the C<~~> operator to also
685understand numeric (and maybe alphanumeric) ranges.
a393eb28
RGS
686
687=head2 A does() built-in
688
689Like ref(), only useful. It would call the C<DOES> method on objects; it
690would also tell whether something can be dereferenced as an
691array/hash/etc., or used as a regexp, etc.
692L<http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/2007-03/msg00481.html>
693
694=head2 Tied filehandles and write() don't mix
695
696There is no method on tied filehandles to allow them to be called back by
697formats.
4fedb12c 698
d10fc472 699=head2 Attach/detach debugger from running program
1626a787 700
cd793d32
NC
701The old perltodo notes "With C<gdb>, you can attach the debugger to a running
702program if you pass the process ID. It would be good to do this with the Perl
0bdfc961
NC
703debugger on a running Perl program, although I'm not sure how it would be
704done." ssh and screen do this with named pipes in /tmp. Maybe we can too.
1626a787 705
a8cb5b9e
RGS
706=head2 Optimize away empty destructors
707
708Defining an empty DESTROY method might be useful (notably in
709AUTOLOAD-enabled classes), but it's still a bit expensive to call. That
710could probably be optimized.
711
0bdfc961
NC
712=head2 LVALUE functions for lists
713
714The old perltodo notes that lvalue functions don't work for list or hash
715slices. This would be good to fix.
716
717=head2 LVALUE functions in the debugger
718
719The old perltodo notes that lvalue functions don't work in the debugger. This
720would be good to fix.
721
0bdfc961
NC
722=head2 regexp optimiser optional
723
724The regexp optimiser is not optional. It should configurable to be, to allow
725its performance to be measured, and its bugs to be easily demonstrated.
726
02f21748
RGS
727=head2 delete &function
728
729Allow to delete functions. One can already undef them, but they're still
730in the stash.
731
ef36c6a7
RGS
732=head2 C</w> regex modifier
733
734That flag would enable to match whole words, and also to interpolate
735arrays as alternations. With it, C</P/w> would be roughly equivalent to:
736
737 do { local $"='|'; /\b(?:P)\b/ }
738
739See L<http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/2007-01/msg00400.html>
740for the discussion.
741
0bdfc961
NC
742=head2 optional optimizer
743
744Make the peephole optimizer optional. Currently it performs two tasks as
745it walks the optree - genuine peephole optimisations, and necessary fixups of
746ops. It would be good to find an efficient way to switch out the
747optimisations whilst keeping the fixups.
748
749=head2 You WANT *how* many
750
751Currently contexts are void, scalar and list. split has a special mechanism in
752place to pass in the number of return values wanted. It would be useful to
753have a general mechanism for this, backwards compatible and little speed hit.
754This would allow proposals such as short circuiting sort to be implemented
755as a module on CPAN.
756
757=head2 lexical aliases
758
759Allow lexical aliases (maybe via the syntax C<my \$alias = \$foo>.
760
761=head2 entersub XS vs Perl
762
763At the moment pp_entersub is huge, and has code to deal with entering both
764perl and XS subroutines. Subroutine implementations rarely change between
765perl and XS at run time, so investigate using 2 ops to enter subs (one for
766XS, one for perl) and swap between if a sub is redefined.
2810d901
NC
767
768=head2 Self ties
769
770self ties are currently illegal because they caused too many segfaults. Maybe
771the causes of these could be tracked down and self-ties on all types re-
772instated.
0bdfc961
NC
773
774=head2 Optimize away @_
775
776The old perltodo notes "Look at the "reification" code in C<av.c>".
777
16fc99ce
NC
778=head2 Properly Unicode safe tokeniser and pads.
779
780The tokeniser isn't actually very UTF-8 clean. C<use utf8;> is a hack -
781variable names are stored in stashes as raw bytes, without the utf-8 flag
782set. The pad API only takes a C<char *> pointer, so that's all bytes too. The
783tokeniser ignores the UTF-8-ness of C<PL_rsfp>, or any SVs returned from
784source filters. All this could be fixed.
785
f092b1f4
RGS
786=head2 The yada yada yada operators
787
788Perl 6's Synopsis 3 says:
789
790I<The ... operator is the "yada, yada, yada" list operator, which is used as
791the body in function prototypes. It complains bitterly (by calling fail)
792if it is ever executed. Variant ??? calls warn, and !!! calls die.>
793
794Those would be nice to add to Perl 5. That could be done without new ops.
795
87a942b1
JH
796=head2 Virtualize operating system access
797
798Implement a set of "vtables" that virtualizes operating system access
799(open(), mkdir(), unlink(), readdir(), getenv(), etc.) At the very
800least these interfaces should take SVs as "name" arguments instead of
801bare char pointers; probably the most flexible and extensible way
e1a3d5d1
JH
802would be for the Perl-facing interfaces to accept HVs. The system
803needs to be per-operating-system and per-file-system
804hookable/filterable, preferably both from XS and Perl level
87a942b1
JH
805(L<perlport/"Files and Filesystems"> is good reading at this point,
806in fact, all of L<perlport> is.)
807
e1a3d5d1
JH
808This has actually already been implemented (but only for Win32),
809take a look at F<iperlsys.h> and F<win32/perlhost.h>. While all Win32
810variants go through a set of "vtables" for operating system access,
811non-Win32 systems currently go straight for the POSIX/UNIX-style
812system/library call. Similar system as for Win32 should be
813implemented for all platforms. The existing Win32 implementation
814probably does not need to survive alongside this proposed new
815implementation, the approaches could be merged.
87a942b1
JH
816
817What would this give us? One often-asked-for feature this would
94da6c29
JH
818enable is using Unicode for filenames, and other "names" like %ENV,
819usernames, hostnames, and so forth.
820(See L<perlunicode/"When Unicode Does Not Happen">.)
821
822But this kind of virtualization would also allow for things like
823virtual filesystems, virtual networks, and "sandboxes" (though as long
824as dynamic loading of random object code is allowed, not very safe
825sandboxes since external code of course know not of Perl's vtables).
826An example of a smaller "sandbox" is that this feature can be used to
827implement per-thread working directories: Win32 already does this.
828
829See also L</"Extend PerlIO and PerlIO::Scalar">.
87a942b1 830
ac6197af
NC
831=head2 Investigate PADTMP hash pessimisation
832
833The peephole optimier converts constants used for hash key lookups to shared
834hash key scalars. Under ithreads, something is undoing this work. See
835See http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/2007-09/msg00793.html
836
0bdfc961
NC
837=head1 Big projects
838
839Tasks that will get your name mentioned in the description of the "Highlights
87a942b1 840of 5.12"
0bdfc961
NC
841
842=head2 make ithreads more robust
843
4e577f8b 844Generally make ithreads more robust. See also L</iCOW>
0bdfc961
NC
845
846This task is incremental - even a little bit of work on it will help, and
847will be greatly appreciated.
848
6c047da7
YST
849One bit would be to write the missing code in sv.c:Perl_dirp_dup.
850
59c7f7d5
RGS
851Fix Perl_sv_dup, et al so that threads can return objects.
852
0bdfc961
NC
853=head2 iCOW
854
855Sarathy and Arthur have a proposal for an improved Copy On Write which
856specifically will be able to COW new ithreads. If this can be implemented
857it would be a good thing.
858
859=head2 (?{...}) closures in regexps
860
861Fix (or rewrite) the implementation of the C</(?{...})/> closures.
862
863=head2 A re-entrant regexp engine
864
865This will allow the use of a regex from inside (?{ }), (??{ }) and
866(?(?{ })|) constructs.
6bda09f9 867
6bda09f9
YO
868=head2 Add class set operations to regexp engine
869
870Apparently these are quite useful. Anyway, Jeffery Friedl wants them.
871
872demerphq has this on his todo list, but right at the bottom.