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