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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
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341=head2 -Duse32bit*
342
343Natively 64-bit systems need neither -Duse64bitint nor -Duse64bitall.
344On these systems, it might be the default compilation mode, and there
345is currently no guarantee that passing no use64bitall option to the
346Configure process will build a 32bit perl. Implementing -Duse32bit*
347options would be nice for perl 5.12.
348
0bdfc961 349=head2 Make it clear from -v if this is the exact official release
89007cb3 350
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351Currently perl from C<p4>/C<rsync> ships with a F<patchlevel.h> file that
352usually defines one local patch, of the form "MAINT12345" or "RC1". The output
353of perl -v doesn't report that a perl isn't an official release, and this
89007cb3 354information can get lost in bugs reports. Because of this, the minor version
fa11829f 355isn't bumped up until RC time, to minimise the possibility of versions of perl
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356escaping that believe themselves to be newer than they actually are.
357
358It would be useful to find an elegant way to have the "this is an interim
359maintenance release" or "this is a release candidate" in the terse -v output,
360and have it so that it's easy for the pumpking to remove this just as the
361release tarball is rolled up. This way the version pulled out of rsync would
362always say "I'm a development release" and it would be safe to bump the
363reported minor version as soon as a release ships, which would aid perl
364developers.
365
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366This task is really about thinking of an elegant way to arrange the C source
367such that it's trivial for the Pumpking to flag "this is an official release"
368when making a tarball, yet leave the default source saying "I'm not the
369official release".
370
fee0a0f7 371=head2 Profile Perl - am I hot or not?
62403a3c 372
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373The Perl source code is stable enough that it makes sense to profile it,
374identify and optimise the hotspots. It would be good to measure the
375performance of the Perl interpreter using free tools such as cachegrind,
376gprof, and dtrace, and work to reduce the bottlenecks they reveal.
377
378As part of this, the idea of F<pp_hot.c> is that it contains the I<hot> ops,
379the ops that are most commonly used. The idea is that by grouping them, their
380object code will be adjacent in the executable, so they have a greater chance
381of already being in the CPU cache (or swapped in) due to being near another op
382already in use.
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383
384Except that it's not clear if these really are the most commonly used ops. So
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385as part of exercising your skills with coverage and profiling tools you might
386want to determine what ops I<really> are the most commonly used. And in turn
387suggest evictions and promotions to achieve a better F<pp_hot.c>.
62403a3c 388
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389=head2 Allocate OPs from arenas
390
391Currently all new OP structures are individually malloc()ed and free()d.
392All C<malloc> implementations have space overheads, and are now as fast as
393custom allocates so it would both use less memory and less CPU to allocate
394the various OP structures from arenas. The SV arena code can probably be
395re-used for this.
396
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397Note that Configuring perl with C<-Accflags=-DPL_OP_SLAB_ALLOC> will use
398Perl_Slab_alloc() to pack optrees into a contiguous block, which is
399probably superior to the use of OP arenas, esp. from a cache locality
400standpoint. See L<Profile Perl - am I hot or not?>.
401
a229ae3b 402=head2 Improve win32/wince.c
0bdfc961 403
a229ae3b 404Currently, numerous functions look virtually, if not completely,
02f21748 405identical in both C<win32/wince.c> and C<win32/win32.c> files, which can't
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406be good.
407
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408=head2 Use secure CRT functions when building with VC8 on Win32
409
410Visual C++ 2005 (VC++ 8.x) deprecated a number of CRT functions on the basis
411that they were "unsafe" and introduced differently named secure versions of
412them as replacements, e.g. instead of writing
413
414 FILE* f = fopen(__FILE__, "r");
415
416one should now write
417
418 FILE* f;
419 errno_t err = fopen_s(&f, __FILE__, "r");
420
421Currently, the warnings about these deprecations have been disabled by adding
422-D_CRT_SECURE_NO_DEPRECATE to the CFLAGS. It would be nice to remove that
423warning suppressant and actually make use of the new secure CRT functions.
424
425There is also a similar issue with POSIX CRT function names like fileno having
426been deprecated in favour of ISO C++ conformant names like _fileno. These
26a6faa8 427warnings are also currently suppressed by adding -D_CRT_NONSTDC_NO_DEPRECATE. It
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428might be nice to do as Microsoft suggest here too, although, unlike the secure
429functions issue, there is presumably little or no benefit in this case.
430
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431=head2 __FUNCTION__ for MSVC-pre-7.0
432
433Jarkko notes that one can things morally equivalent to C<__FUNCTION__>
434(or C<__func__>) even in MSVC-pre-7.0, contrary to popular belief.
435See L<http://www.codeproject.com/debug/extendedtrace.asp> if you feel like
436making C<PERL_MEM_LOG> more useful on Win32.
437
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438=head1 Tasks that need a knowledge of XS
439
440These tasks would need C knowledge, and roughly the level of knowledge of
441the perl API that comes from writing modules that use XS to interface to
442C.
443
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444=head2 autovivification
445
446Make all autovivification consistent w.r.t LVALUE/RVALUE and strict/no strict;
447
448This task is incremental - even a little bit of work on it will help.
449
450=head2 Unicode in Filenames
451
452chdir, chmod, chown, chroot, exec, glob, link, lstat, mkdir, open,
453opendir, qx, readdir, readlink, rename, rmdir, stat, symlink, sysopen,
454system, truncate, unlink, utime, -X. All these could potentially accept
455Unicode filenames either as input or output (and in the case of system
456and qx Unicode in general, as input or output to/from the shell).
457Whether a filesystem - an operating system pair understands Unicode in
458filenames varies.
459
460Known combinations that have some level of understanding include
461Microsoft NTFS, Apple HFS+ (In Mac OS 9 and X) and Apple UFS (in Mac
462OS X), NFS v4 is rumored to be Unicode, and of course Plan 9. How to
463create Unicode filenames, what forms of Unicode are accepted and used
464(UCS-2, UTF-16, UTF-8), what (if any) is the normalization form used,
465and so on, varies. Finding the right level of interfacing to Perl
466requires some thought. Remember that an OS does not implicate a
467filesystem.
468
469(The Windows -C command flag "wide API support" has been at least
470temporarily retired in 5.8.1, and the -C has been repurposed, see
471L<perlrun>.)
472
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473Most probably the right way to do this would be this:
474L</"Virtualize operating system access">.
475
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476=head2 Unicode in %ENV
477
478Currently the %ENV entries are always byte strings.
87a942b1 479See L</"Virtualize operating system access">.
6d71adcd 480
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481=head2 Unicode and glob()
482
483Currently glob patterns and filenames returned from File::Glob::glob()
87a942b1 484are always byte strings. See L</"Virtualize operating system access">.
1f2e7916 485
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486=head2 Unicode and lc/uc operators
487
488Some built-in operators (C<lc>, C<uc>, etc.) behave differently, based on
489what the internal encoding of their argument is. That should not be the
490case. Maybe add a pragma to switch behaviour.
491
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492=head2 use less 'memory'
493
494Investigate trade offs to switch out perl's choices on memory usage.
495Particularly perl should be able to give memory back.
496
497This task is incremental - even a little bit of work on it will help.
498
499=head2 Re-implement C<:unique> in a way that is actually thread-safe
500
501The old implementation made bad assumptions on several levels. A good 90%
502solution might be just to make C<:unique> work to share the string buffer
503of SvPVs. That way large constant strings can be shared between ithreads,
504such as the configuration information in F<Config>.
505
506=head2 Make tainting consistent
507
508Tainting would be easier to use if it didn't take documented shortcuts and
509allow taint to "leak" everywhere within an expression.
510
511=head2 readpipe(LIST)
512
513system() accepts a LIST syntax (and a PROGRAM LIST syntax) to avoid
514running a shell. readpipe() (the function behind qx//) could be similarly
515extended.
516
517=head2 strcat(), strcpy(), strncat(), strncpy(), sprintf(), vsprintf()
518
519Maybe create a utility that checks after each libperl.a creation that
520none of the above (nor sprintf(), vsprintf(), or *SHUDDER* gets())
521ever creep back to libperl.a.
522
523 nm libperl.a | ./miniperl -alne '$o = $F[0] if /:$/; print "$o $F[1]" if $F[0] eq "U" && $F[1] =~ /^(?:strn?c(?:at|py)|v?sprintf|gets)$/'
524
525Note, of course, that this will only tell whether B<your> platform
526is using those naughty interfaces.
527
528=head2 Audit the code for destruction ordering assumptions
529
530Change 25773 notes
531
532 /* Need to check SvMAGICAL, as during global destruction it may be that
533 AvARYLEN(av) has been freed before av, and hence the SvANY() pointer
534 is now part of the linked list of SV heads, rather than pointing to
535 the original body. */
536 /* FIXME - audit the code for other bugs like this one. */
537
538adding the C<SvMAGICAL> check to
539
540 if (AvARYLEN(av) && SvMAGICAL(AvARYLEN(av))) {
541 MAGIC *mg = mg_find (AvARYLEN(av), PERL_MAGIC_arylen);
542
543Go through the core and look for similar assumptions that SVs have particular
544types, as all bets are off during global destruction.
545
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546=head2 Extend PerlIO and PerlIO::Scalar
547
548PerlIO::Scalar doesn't know how to truncate(). Implementing this
549would require extending the PerlIO vtable.
550
551Similarly the PerlIO vtable doesn't know about formats (write()), or
552about stat(), or chmod()/chown(), utime(), or flock().
553
554(For PerlIO::Scalar it's hard to see what e.g. mode bits or ownership
555would mean.)
556
557PerlIO doesn't do directories or symlinks, either: mkdir(), rmdir(),
558opendir(), closedir(), seekdir(), rewinddir(), glob(); symlink(),
559readlink().
560
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561See also L</"Virtualize operating system access">.
562
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563=head2 -C on the #! line
564
565It should be possible to make -C work correctly if found on the #! line,
566given that all perl command line options are strict ASCII, and -C changes
567only the interpretation of non-ASCII characters, and not for the script file
568handle. To make it work needs some investigation of the ordering of function
569calls during startup, and (by implication) a bit of tweaking of that order.
570
571
0bdfc961 572=head1 Tasks that need a knowledge of the interpreter
3298bd4d 573
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574These tasks would need C knowledge, and knowledge of how the interpreter works,
575or a willingness to learn.
3298bd4d 576
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577=head2 state variable initialization in list context
578
579Currently this is illegal:
580
581 state ($a, $b) = foo();
582
583The current Perl 6 design is that C<state ($a) = foo();> and
584C<(state $a) = foo();> have different semantics, which is tricky to implement
585in Perl 5 as currently the produce the same opcode trees. It would be useful
586to clarify that the Perl 6 design is firm, and then implement the necessary
587code in Perl 5. There are comments in C<Perl_newASSIGNOP()> that show the
588code paths taken by various assignment constructions involving state variables.
589
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590=head2 Implement $value ~~ 0 .. $range
591
592It would be nice to extend the syntax of the C<~~> operator to also
593understand numeric (and maybe alphanumeric) ranges.
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594
595=head2 A does() built-in
596
597Like ref(), only useful. It would call the C<DOES> method on objects; it
598would also tell whether something can be dereferenced as an
599array/hash/etc., or used as a regexp, etc.
600L<http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/2007-03/msg00481.html>
601
602=head2 Tied filehandles and write() don't mix
603
604There is no method on tied filehandles to allow them to be called back by
605formats.
4fedb12c 606
d10fc472 607=head2 Attach/detach debugger from running program
1626a787 608
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609The old perltodo notes "With C<gdb>, you can attach the debugger to a running
610program if you pass the process ID. It would be good to do this with the Perl
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611debugger on a running Perl program, although I'm not sure how it would be
612done." ssh and screen do this with named pipes in /tmp. Maybe we can too.
1626a787 613
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614=head2 Optimize away empty destructors
615
616Defining an empty DESTROY method might be useful (notably in
617AUTOLOAD-enabled classes), but it's still a bit expensive to call. That
618could probably be optimized.
619
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620=head2 LVALUE functions for lists
621
622The old perltodo notes that lvalue functions don't work for list or hash
623slices. This would be good to fix.
624
625=head2 LVALUE functions in the debugger
626
627The old perltodo notes that lvalue functions don't work in the debugger. This
628would be good to fix.
629
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630=head2 regexp optimiser optional
631
632The regexp optimiser is not optional. It should configurable to be, to allow
633its performance to be measured, and its bugs to be easily demonstrated.
634
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635=head2 delete &function
636
637Allow to delete functions. One can already undef them, but they're still
638in the stash.
639
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640=head2 C</w> regex modifier
641
642That flag would enable to match whole words, and also to interpolate
643arrays as alternations. With it, C</P/w> would be roughly equivalent to:
644
645 do { local $"='|'; /\b(?:P)\b/ }
646
647See L<http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/2007-01/msg00400.html>
648for the discussion.
649
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650=head2 optional optimizer
651
652Make the peephole optimizer optional. Currently it performs two tasks as
653it walks the optree - genuine peephole optimisations, and necessary fixups of
654ops. It would be good to find an efficient way to switch out the
655optimisations whilst keeping the fixups.
656
657=head2 You WANT *how* many
658
659Currently contexts are void, scalar and list. split has a special mechanism in
660place to pass in the number of return values wanted. It would be useful to
661have a general mechanism for this, backwards compatible and little speed hit.
662This would allow proposals such as short circuiting sort to be implemented
663as a module on CPAN.
664
665=head2 lexical aliases
666
667Allow lexical aliases (maybe via the syntax C<my \$alias = \$foo>.
668
669=head2 entersub XS vs Perl
670
671At the moment pp_entersub is huge, and has code to deal with entering both
672perl and XS subroutines. Subroutine implementations rarely change between
673perl and XS at run time, so investigate using 2 ops to enter subs (one for
674XS, one for perl) and swap between if a sub is redefined.
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675
676=head2 Self ties
677
678self ties are currently illegal because they caused too many segfaults. Maybe
679the causes of these could be tracked down and self-ties on all types re-
680instated.
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681
682=head2 Optimize away @_
683
684The old perltodo notes "Look at the "reification" code in C<av.c>".
685
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686=head2 Properly Unicode safe tokeniser and pads.
687
688The tokeniser isn't actually very UTF-8 clean. C<use utf8;> is a hack -
689variable names are stored in stashes as raw bytes, without the utf-8 flag
690set. The pad API only takes a C<char *> pointer, so that's all bytes too. The
691tokeniser ignores the UTF-8-ness of C<PL_rsfp>, or any SVs returned from
692source filters. All this could be fixed.
693
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694=head2 The yada yada yada operators
695
696Perl 6's Synopsis 3 says:
697
698I<The ... operator is the "yada, yada, yada" list operator, which is used as
699the body in function prototypes. It complains bitterly (by calling fail)
700if it is ever executed. Variant ??? calls warn, and !!! calls die.>
701
702Those would be nice to add to Perl 5. That could be done without new ops.
703
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704=head2 Virtualize operating system access
705
706Implement a set of "vtables" that virtualizes operating system access
707(open(), mkdir(), unlink(), readdir(), getenv(), etc.) At the very
708least these interfaces should take SVs as "name" arguments instead of
709bare char pointers; probably the most flexible and extensible way
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710would be for the Perl-facing interfaces to accept HVs. The system
711needs to be per-operating-system and per-file-system
712hookable/filterable, preferably both from XS and Perl level
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713(L<perlport/"Files and Filesystems"> is good reading at this point,
714in fact, all of L<perlport> is.)
715
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716This has actually already been implemented (but only for Win32),
717take a look at F<iperlsys.h> and F<win32/perlhost.h>. While all Win32
718variants go through a set of "vtables" for operating system access,
719non-Win32 systems currently go straight for the POSIX/UNIX-style
720system/library call. Similar system as for Win32 should be
721implemented for all platforms. The existing Win32 implementation
722probably does not need to survive alongside this proposed new
723implementation, the approaches could be merged.
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724
725What would this give us? One often-asked-for feature this would
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726enable is using Unicode for filenames, and other "names" like %ENV,
727usernames, hostnames, and so forth.
728(See L<perlunicode/"When Unicode Does Not Happen">.)
729
730But this kind of virtualization would also allow for things like
731virtual filesystems, virtual networks, and "sandboxes" (though as long
732as dynamic loading of random object code is allowed, not very safe
733sandboxes since external code of course know not of Perl's vtables).
734An example of a smaller "sandbox" is that this feature can be used to
735implement per-thread working directories: Win32 already does this.
736
737See also L</"Extend PerlIO and PerlIO::Scalar">.
87a942b1 738
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739=head1 Big projects
740
741Tasks that will get your name mentioned in the description of the "Highlights
87a942b1 742of 5.12"
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743
744=head2 make ithreads more robust
745
4e577f8b 746Generally make ithreads more robust. See also L</iCOW>
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747
748This task is incremental - even a little bit of work on it will help, and
749will be greatly appreciated.
750
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751One bit would be to write the missing code in sv.c:Perl_dirp_dup.
752
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753Fix Perl_sv_dup, et al so that threads can return objects.
754
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755=head2 iCOW
756
757Sarathy and Arthur have a proposal for an improved Copy On Write which
758specifically will be able to COW new ithreads. If this can be implemented
759it would be a good thing.
760
761=head2 (?{...}) closures in regexps
762
763Fix (or rewrite) the implementation of the C</(?{...})/> closures.
764
765=head2 A re-entrant regexp engine
766
767This will allow the use of a regex from inside (?{ }), (??{ }) and
768(?(?{ })|) constructs.
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770=head2 Add class set operations to regexp engine
771
772Apparently these are quite useful. Anyway, Jeffery Friedl wants them.
773
774demerphq has this on his todo list, but right at the bottom.