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1=head1 NAME
2
3perltodo - Perl TO-DO List
4
5=head1 DESCRIPTION
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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
0bdfc961 90=head2 A decent benchmark
e50bb9a1 91
617eabfa 92C<perlbench> seems impervious to any recent changes made to the perl core. It
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93would be useful to have a reasonable general benchmarking suite that roughly
94represented what current perl programs do, and measurably reported whether
95tweaks to the core improve, degrade or don't really affect performance, to
96guide people attempting to optimise the guts of perl. Gisle would welcome
97new tests for perlbench.
6168cf99 98
0bdfc961 99=head2 fix tainting bugs
6168cf99 100
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101Fix the bugs revealed by running the test suite with the C<-t> switch (via
102C<make test.taintwarn>).
e50bb9a1 103
0bdfc961 104=head2 Dual life everything
e50bb9a1 105
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106As part of the "dists" plan, anything that doesn't belong in the smallest perl
107distribution needs to be dual lifed. Anything else can be too. Figure out what
108changes would be needed to package that module and its tests up for CPAN, and
109do so. Test it with older perl releases, and fix the problems you find.
e50bb9a1 110
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111To make a minimal perl distribution, it's useful to look at
112F<t/lib/commonsense.t>.
113
0bdfc961 114=head2 Improving C<threads::shared>
722d2a37 115
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116Investigate whether C<threads::shared> could share aggregates properly with
117only Perl level changes to shared.pm
722d2a37 118
0bdfc961 119=head2 POSIX memory footprint
e50bb9a1 120
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121Ilya observed that use POSIX; eats memory like there's no tomorrow, and at
122various times worked to cut it down. There is probably still fat to cut out -
123for example POSIX passes Exporter some very memory hungry data structures.
e50bb9a1 124
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125=head2 embed.pl/makedef.pl
126
127There is a script F<embed.pl> that generates several header files to prefix
128all of Perl's symbols in a consistent way, to provide some semblance of
129namespace support in C<C>. Functions are declared in F<embed.fnc>, variables
907b3e23 130in F<interpvar.h>. Quite a few of the functions and variables
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131are conditionally declared there, using C<#ifdef>. However, F<embed.pl>
132doesn't understand the C macros, so the rules about which symbols are present
133when is duplicated in F<makedef.pl>. Writing things twice is bad, m'kay.
134It would be good to teach C<embed.pl> to understand the conditional
135compilation, and hence remove the duplication, and the mistakes it has caused.
e50bb9a1 136
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137=head2 use strict; and AutoLoad
138
139Currently if you write
140
141 package Whack;
142 use AutoLoader 'AUTOLOAD';
143 use strict;
144 1;
145 __END__
146 sub bloop {
147 print join (' ', No, strict, here), "!\n";
148 }
149
150then C<use strict;> isn't in force within the autoloaded subroutines. It would
151be more consistent (and less surprising) to arrange for all lexical pragmas
152in force at the __END__ block to be in force within each autoloaded subroutine.
153
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154There's a similar problem with SelfLoader.
155
0bdfc961 156=head1 Tasks that need a little sysadmin-type knowledge
e50bb9a1 157
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158Or if you prefer, tasks that you would learn from, and broaden your skills
159base...
e50bb9a1 160
cd793d32 161=head2 make HTML install work
e50bb9a1 162
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163There is an C<installhtml> target in the Makefile. It's marked as
164"experimental". It would be good to get this tested, make it work reliably, and
165remove the "experimental" tag. This would include
166
167=over 4
168
169=item 1
170
171Checking that cross linking between various parts of the documentation works.
172In particular that links work between the modules (files with POD in F<lib/>)
173and the core documentation (files in F<pod/>)
174
175=item 2
176
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177Work out how to split C<perlfunc> into chunks, preferably one per function
178group, preferably with general case code that could be used elsewhere.
179Challenges here are correctly identifying the groups of functions that go
180together, and making the right named external cross-links point to the right
181page. Things to be aware of are C<-X>, groups such as C<getpwnam> to
182C<endservent>, two or more C<=items> giving the different parameter lists, such
183as
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184
185 =item substr EXPR,OFFSET,LENGTH,REPLACEMENT
adebf063 186 =item substr EXPR,OFFSET,LENGTH
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187 =item substr EXPR,OFFSET
188
189and different parameter lists having different meanings. (eg C<select>)
190
191=back
3a89a73c 192
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193=head2 compressed man pages
194
195Be able to install them. This would probably need a configure test to see how
196the system does compressed man pages (same directory/different directory?
197same filename/different filename), as well as tweaking the F<installman> script
198to compress as necessary.
199
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200=head2 Add a code coverage target to the Makefile
201
202Make it easy for anyone to run Devel::Cover on the core's tests. The steps
203to do this manually are roughly
204
205=over 4
206
207=item *
208
209do a normal C<Configure>, but include Devel::Cover as a module to install
210(see F<INSTALL> for how to do this)
211
212=item *
213
214 make perl
215
216=item *
217
218 cd t; HARNESS_PERL_SWITCHES=-MDevel::Cover ./perl -I../lib harness
219
220=item *
221
222Process the resulting Devel::Cover database
223
224=back
225
226This just give you the coverage of the F<.pm>s. To also get the C level
227coverage you need to
228
229=over 4
230
231=item *
232
233Additionally tell C<Configure> to use the appropriate C compiler flags for
234C<gcov>
235
236=item *
237
238 make perl.gcov
239
240(instead of C<make perl>)
241
242=item *
243
244After running the tests run C<gcov> to generate all the F<.gcov> files.
245(Including down in the subdirectories of F<ext/>
246
247=item *
248
249(From the top level perl directory) run C<gcov2perl> on all the C<.gcov> files
250to get their stats into the cover_db directory.
251
252=item *
253
254Then process the Devel::Cover database
255
256=back
257
258It would be good to add a single switch to C<Configure> to specify that you
259wanted to perform perl level coverage, and another to specify C level
260coverage, and have C<Configure> and the F<Makefile> do all the right things
261automatically.
262
02f21748 263=head2 Make Config.pm cope with differences between built and installed perl
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264
265Quite often vendors ship a perl binary compiled with their (pay-for)
266compilers. People install a free compiler, such as gcc. To work out how to
267build extensions, Perl interrogates C<%Config>, so in this situation
268C<%Config> describes compilers that aren't there, and extension building
269fails. This forces people into choosing between re-compiling perl themselves
270using the compiler they have, or only using modules that the vendor ships.
271
272It would be good to find a way teach C<Config.pm> about the installation setup,
273possibly involving probing at install time or later, so that the C<%Config> in
274a binary distribution better describes the installed machine, when the
275installed machine differs from the build machine in some significant way.
276
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277=head2 linker specification files
278
279Some platforms mandate that you provide a list of a shared library's external
280symbols to the linker, so the core already has the infrastructure in place to
281do this for generating shared perl libraries. My understanding is that the
282GNU toolchain can accept an optional linker specification file, and restrict
283visibility just to symbols declared in that file. It would be good to extend
284F<makedef.pl> to support this format, and to provide a means within
285C<Configure> to enable it. This would allow Unix users to test that the
286export list is correct, and to build a perl that does not pollute the global
287namespace with private symbols.
288
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289=head2 Cross-compile support
290
291Currently C<Configure> understands C<-Dusecrosscompile> option. This option
292arranges for building C<miniperl> for TARGET machine, so this C<miniperl> is
293assumed then to be copied to TARGET machine and used as a replacement of full
294C<perl> executable.
295
d1307786 296This could be done little differently. Namely C<miniperl> should be built for
a229ae3b 297HOST and then full C<perl> with extensions should be compiled for TARGET.
d1307786 298This, however, might require extra trickery for %Config: we have one config
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299first for HOST and then another for TARGET. Tools like MakeMaker will be
300mightily confused. Having around two different types of executables and
301libraries (HOST and TARGET) makes life interesting for Makefiles and
302shell (and Perl) scripts. There is $Config{run}, normally empty, which
303can be used as an execution wrapper. Also note that in some
304cross-compilation/execution environments the HOST and the TARGET do
305not see the same filesystem(s), the $Config{run} may need to do some
306file/directory copying back and forth.
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307
308=head1 Tasks that need a little C knowledge
309
310These tasks would need a little C knowledge, but don't need any specific
311background or experience with XS, or how the Perl interpreter works
312
313=head2 Make it clear from -v if this is the exact official release
89007cb3 314
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315Currently perl from C<p4>/C<rsync> ships with a F<patchlevel.h> file that
316usually defines one local patch, of the form "MAINT12345" or "RC1". The output
317of perl -v doesn't report that a perl isn't an official release, and this
89007cb3 318information can get lost in bugs reports. Because of this, the minor version
fa11829f 319isn't bumped up until RC time, to minimise the possibility of versions of perl
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320escaping that believe themselves to be newer than they actually are.
321
322It would be useful to find an elegant way to have the "this is an interim
323maintenance release" or "this is a release candidate" in the terse -v output,
324and have it so that it's easy for the pumpking to remove this just as the
325release tarball is rolled up. This way the version pulled out of rsync would
326always say "I'm a development release" and it would be safe to bump the
327reported minor version as soon as a release ships, which would aid perl
328developers.
329
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330This task is really about thinking of an elegant way to arrange the C source
331such that it's trivial for the Pumpking to flag "this is an official release"
332when making a tarball, yet leave the default source saying "I'm not the
333official release".
334
fee0a0f7 335=head2 Profile Perl - am I hot or not?
62403a3c 336
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337The Perl source code is stable enough that it makes sense to profile it,
338identify and optimise the hotspots. It would be good to measure the
339performance of the Perl interpreter using free tools such as cachegrind,
340gprof, and dtrace, and work to reduce the bottlenecks they reveal.
341
342As part of this, the idea of F<pp_hot.c> is that it contains the I<hot> ops,
343the ops that are most commonly used. The idea is that by grouping them, their
344object code will be adjacent in the executable, so they have a greater chance
345of already being in the CPU cache (or swapped in) due to being near another op
346already in use.
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347
348Except that it's not clear if these really are the most commonly used ops. So
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349as part of exercising your skills with coverage and profiling tools you might
350want to determine what ops I<really> are the most commonly used. And in turn
351suggest evictions and promotions to achieve a better F<pp_hot.c>.
62403a3c 352
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353=head2 Allocate OPs from arenas
354
355Currently all new OP structures are individually malloc()ed and free()d.
356All C<malloc> implementations have space overheads, and are now as fast as
357custom allocates so it would both use less memory and less CPU to allocate
358the various OP structures from arenas. The SV arena code can probably be
359re-used for this.
360
a229ae3b 361=head2 Improve win32/wince.c
0bdfc961 362
a229ae3b 363Currently, numerous functions look virtually, if not completely,
02f21748 364identical in both C<win32/wince.c> and C<win32/win32.c> files, which can't
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365be good.
366
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367=head2 Use secure CRT functions when building with VC8 on Win32
368
369Visual C++ 2005 (VC++ 8.x) deprecated a number of CRT functions on the basis
370that they were "unsafe" and introduced differently named secure versions of
371them as replacements, e.g. instead of writing
372
373 FILE* f = fopen(__FILE__, "r");
374
375one should now write
376
377 FILE* f;
378 errno_t err = fopen_s(&f, __FILE__, "r");
379
380Currently, the warnings about these deprecations have been disabled by adding
381-D_CRT_SECURE_NO_DEPRECATE to the CFLAGS. It would be nice to remove that
382warning suppressant and actually make use of the new secure CRT functions.
383
384There is also a similar issue with POSIX CRT function names like fileno having
385been deprecated in favour of ISO C++ conformant names like _fileno. These
26a6faa8 386warnings are also currently suppressed by adding -D_CRT_NONSTDC_NO_DEPRECATE. It
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387might be nice to do as Microsoft suggest here too, although, unlike the secure
388functions issue, there is presumably little or no benefit in this case.
389
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390=head1 Tasks that need a knowledge of XS
391
392These tasks would need C knowledge, and roughly the level of knowledge of
393the perl API that comes from writing modules that use XS to interface to
394C.
395
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396=head2 autovivification
397
398Make all autovivification consistent w.r.t LVALUE/RVALUE and strict/no strict;
399
400This task is incremental - even a little bit of work on it will help.
401
402=head2 Unicode in Filenames
403
404chdir, chmod, chown, chroot, exec, glob, link, lstat, mkdir, open,
405opendir, qx, readdir, readlink, rename, rmdir, stat, symlink, sysopen,
406system, truncate, unlink, utime, -X. All these could potentially accept
407Unicode filenames either as input or output (and in the case of system
408and qx Unicode in general, as input or output to/from the shell).
409Whether a filesystem - an operating system pair understands Unicode in
410filenames varies.
411
412Known combinations that have some level of understanding include
413Microsoft NTFS, Apple HFS+ (In Mac OS 9 and X) and Apple UFS (in Mac
414OS X), NFS v4 is rumored to be Unicode, and of course Plan 9. How to
415create Unicode filenames, what forms of Unicode are accepted and used
416(UCS-2, UTF-16, UTF-8), what (if any) is the normalization form used,
417and so on, varies. Finding the right level of interfacing to Perl
418requires some thought. Remember that an OS does not implicate a
419filesystem.
420
421(The Windows -C command flag "wide API support" has been at least
422temporarily retired in 5.8.1, and the -C has been repurposed, see
423L<perlrun>.)
424
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425Most probably the right way to do this would be this:
426L</"Virtualize operating system access">.
427
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428=head2 Unicode in %ENV
429
430Currently the %ENV entries are always byte strings.
87a942b1 431See L</"Virtualize operating system access">.
6d71adcd 432
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433=head2 Unicode and glob()
434
435Currently glob patterns and filenames returned from File::Glob::glob()
87a942b1 436are always byte strings. See L</"Virtualize operating system access">.
1f2e7916 437
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438=head2 Unicode and lc/uc operators
439
440Some built-in operators (C<lc>, C<uc>, etc.) behave differently, based on
441what the internal encoding of their argument is. That should not be the
442case. Maybe add a pragma to switch behaviour.
443
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444=head2 use less 'memory'
445
446Investigate trade offs to switch out perl's choices on memory usage.
447Particularly perl should be able to give memory back.
448
449This task is incremental - even a little bit of work on it will help.
450
451=head2 Re-implement C<:unique> in a way that is actually thread-safe
452
453The old implementation made bad assumptions on several levels. A good 90%
454solution might be just to make C<:unique> work to share the string buffer
455of SvPVs. That way large constant strings can be shared between ithreads,
456such as the configuration information in F<Config>.
457
458=head2 Make tainting consistent
459
460Tainting would be easier to use if it didn't take documented shortcuts and
461allow taint to "leak" everywhere within an expression.
462
463=head2 readpipe(LIST)
464
465system() accepts a LIST syntax (and a PROGRAM LIST syntax) to avoid
466running a shell. readpipe() (the function behind qx//) could be similarly
467extended.
468
469=head2 strcat(), strcpy(), strncat(), strncpy(), sprintf(), vsprintf()
470
471Maybe create a utility that checks after each libperl.a creation that
472none of the above (nor sprintf(), vsprintf(), or *SHUDDER* gets())
473ever creep back to libperl.a.
474
475 nm libperl.a | ./miniperl -alne '$o = $F[0] if /:$/; print "$o $F[1]" if $F[0] eq "U" && $F[1] =~ /^(?:strn?c(?:at|py)|v?sprintf|gets)$/'
476
477Note, of course, that this will only tell whether B<your> platform
478is using those naughty interfaces.
479
480=head2 Audit the code for destruction ordering assumptions
481
482Change 25773 notes
483
484 /* Need to check SvMAGICAL, as during global destruction it may be that
485 AvARYLEN(av) has been freed before av, and hence the SvANY() pointer
486 is now part of the linked list of SV heads, rather than pointing to
487 the original body. */
488 /* FIXME - audit the code for other bugs like this one. */
489
490adding the C<SvMAGICAL> check to
491
492 if (AvARYLEN(av) && SvMAGICAL(AvARYLEN(av))) {
493 MAGIC *mg = mg_find (AvARYLEN(av), PERL_MAGIC_arylen);
494
495Go through the core and look for similar assumptions that SVs have particular
496types, as all bets are off during global destruction.
497
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498=head2 Extend PerlIO and PerlIO::Scalar
499
500PerlIO::Scalar doesn't know how to truncate(). Implementing this
501would require extending the PerlIO vtable.
502
503Similarly the PerlIO vtable doesn't know about formats (write()), or
504about stat(), or chmod()/chown(), utime(), or flock().
505
506(For PerlIO::Scalar it's hard to see what e.g. mode bits or ownership
507would mean.)
508
509PerlIO doesn't do directories or symlinks, either: mkdir(), rmdir(),
510opendir(), closedir(), seekdir(), rewinddir(), glob(); symlink(),
511readlink().
512
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513See also L</"Virtualize operating system access">.
514
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515=head2 -C on the #! line
516
517It should be possible to make -C work correctly if found on the #! line,
518given that all perl command line options are strict ASCII, and -C changes
519only the interpretation of non-ASCII characters, and not for the script file
520handle. To make it work needs some investigation of the ordering of function
521calls during startup, and (by implication) a bit of tweaking of that order.
522
523
0bdfc961 524=head1 Tasks that need a knowledge of the interpreter
3298bd4d 525
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526These tasks would need C knowledge, and knowledge of how the interpreter works,
527or a willingness to learn.
3298bd4d 528
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529=head2 Implement $value ~~ 0 .. $range
530
531It would be nice to extend the syntax of the C<~~> operator to also
532understand numeric (and maybe alphanumeric) ranges.
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533
534=head2 A does() built-in
535
536Like ref(), only useful. It would call the C<DOES> method on objects; it
537would also tell whether something can be dereferenced as an
538array/hash/etc., or used as a regexp, etc.
539L<http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/2007-03/msg00481.html>
540
541=head2 Tied filehandles and write() don't mix
542
543There is no method on tied filehandles to allow them to be called back by
544formats.
4fedb12c 545
d10fc472 546=head2 Attach/detach debugger from running program
1626a787 547
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548The old perltodo notes "With C<gdb>, you can attach the debugger to a running
549program if you pass the process ID. It would be good to do this with the Perl
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550debugger on a running Perl program, although I'm not sure how it would be
551done." ssh and screen do this with named pipes in /tmp. Maybe we can too.
1626a787 552
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553=head2 Optimize away empty destructors
554
555Defining an empty DESTROY method might be useful (notably in
556AUTOLOAD-enabled classes), but it's still a bit expensive to call. That
557could probably be optimized.
558
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559=head2 LVALUE functions for lists
560
561The old perltodo notes that lvalue functions don't work for list or hash
562slices. This would be good to fix.
563
564=head2 LVALUE functions in the debugger
565
566The old perltodo notes that lvalue functions don't work in the debugger. This
567would be good to fix.
568
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569=head2 regexp optimiser optional
570
571The regexp optimiser is not optional. It should configurable to be, to allow
572its performance to be measured, and its bugs to be easily demonstrated.
573
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574=head2 delete &function
575
576Allow to delete functions. One can already undef them, but they're still
577in the stash.
578
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579=head2 C</w> regex modifier
580
581That flag would enable to match whole words, and also to interpolate
582arrays as alternations. With it, C</P/w> would be roughly equivalent to:
583
584 do { local $"='|'; /\b(?:P)\b/ }
585
586See L<http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/2007-01/msg00400.html>
587for the discussion.
588
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589=head2 optional optimizer
590
591Make the peephole optimizer optional. Currently it performs two tasks as
592it walks the optree - genuine peephole optimisations, and necessary fixups of
593ops. It would be good to find an efficient way to switch out the
594optimisations whilst keeping the fixups.
595
596=head2 You WANT *how* many
597
598Currently contexts are void, scalar and list. split has a special mechanism in
599place to pass in the number of return values wanted. It would be useful to
600have a general mechanism for this, backwards compatible and little speed hit.
601This would allow proposals such as short circuiting sort to be implemented
602as a module on CPAN.
603
604=head2 lexical aliases
605
606Allow lexical aliases (maybe via the syntax C<my \$alias = \$foo>.
607
608=head2 entersub XS vs Perl
609
610At the moment pp_entersub is huge, and has code to deal with entering both
611perl and XS subroutines. Subroutine implementations rarely change between
612perl and XS at run time, so investigate using 2 ops to enter subs (one for
613XS, one for perl) and swap between if a sub is redefined.
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614
615=head2 Self ties
616
617self ties are currently illegal because they caused too many segfaults. Maybe
618the causes of these could be tracked down and self-ties on all types re-
619instated.
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620
621=head2 Optimize away @_
622
623The old perltodo notes "Look at the "reification" code in C<av.c>".
624
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625=head2 Properly Unicode safe tokeniser and pads.
626
627The tokeniser isn't actually very UTF-8 clean. C<use utf8;> is a hack -
628variable names are stored in stashes as raw bytes, without the utf-8 flag
629set. The pad API only takes a C<char *> pointer, so that's all bytes too. The
630tokeniser ignores the UTF-8-ness of C<PL_rsfp>, or any SVs returned from
631source filters. All this could be fixed.
632
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633=head2 The yada yada yada operators
634
635Perl 6's Synopsis 3 says:
636
637I<The ... operator is the "yada, yada, yada" list operator, which is used as
638the body in function prototypes. It complains bitterly (by calling fail)
639if it is ever executed. Variant ??? calls warn, and !!! calls die.>
640
641Those would be nice to add to Perl 5. That could be done without new ops.
642
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643=head2 Virtualize operating system access
644
645Implement a set of "vtables" that virtualizes operating system access
646(open(), mkdir(), unlink(), readdir(), getenv(), etc.) At the very
647least these interfaces should take SVs as "name" arguments instead of
648bare char pointers; probably the most flexible and extensible way
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649would be for the Perl-facing interfaces to accept HVs. The system
650needs to be per-operating-system and per-file-system
651hookable/filterable, preferably both from XS and Perl level
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652(L<perlport/"Files and Filesystems"> is good reading at this point,
653in fact, all of L<perlport> is.)
654
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655This has actually already been implemented (but only for Win32),
656take a look at F<iperlsys.h> and F<win32/perlhost.h>. While all Win32
657variants go through a set of "vtables" for operating system access,
658non-Win32 systems currently go straight for the POSIX/UNIX-style
659system/library call. Similar system as for Win32 should be
660implemented for all platforms. The existing Win32 implementation
661probably does not need to survive alongside this proposed new
662implementation, the approaches could be merged.
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663
664What would this give us? One often-asked-for feature this would
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665enable is using Unicode for filenames, and other "names" like %ENV,
666usernames, hostnames, and so forth.
667(See L<perlunicode/"When Unicode Does Not Happen">.)
668
669But this kind of virtualization would also allow for things like
670virtual filesystems, virtual networks, and "sandboxes" (though as long
671as dynamic loading of random object code is allowed, not very safe
672sandboxes since external code of course know not of Perl's vtables).
673An example of a smaller "sandbox" is that this feature can be used to
674implement per-thread working directories: Win32 already does this.
675
676See also L</"Extend PerlIO and PerlIO::Scalar">.
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678=head1 Big projects
679
680Tasks that will get your name mentioned in the description of the "Highlights
87a942b1 681of 5.12"
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682
683=head2 make ithreads more robust
684
4e577f8b 685Generally make ithreads more robust. See also L</iCOW>
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686
687This task is incremental - even a little bit of work on it will help, and
688will be greatly appreciated.
689
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690One bit would be to write the missing code in sv.c:Perl_dirp_dup.
691
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692Fix Perl_sv_dup, et al so that threads can return objects.
693
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694=head2 iCOW
695
696Sarathy and Arthur have a proposal for an improved Copy On Write which
697specifically will be able to COW new ithreads. If this can be implemented
698it would be a good thing.
699
700=head2 (?{...}) closures in regexps
701
702Fix (or rewrite) the implementation of the C</(?{...})/> closures.
703
704=head2 A re-entrant regexp engine
705
706This will allow the use of a regex from inside (?{ }), (??{ }) and
707(?(?{ })|) constructs.
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709=head2 Add class set operations to regexp engine
710
711Apparently these are quite useful. Anyway, Jeffery Friedl wants them.
712
713demerphq has this on his todo list, but right at the bottom.