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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
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25=head2 Remove duplication of test setup.
26
27Schwern notes, that there's duplication of code - lots and lots of tests have
28some variation on the big block of C<$Is_Foo> checks. We can safely put this
29into a file, change it to build an C<%Is> hash and require it. Maybe just put
30it into F<test.pl>. Throw in the handy tainting subroutines.
31
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32=head2 merge common code in installperl and installman
33
34There are some common subroutines and a common C<BEGIN> block in F<installperl>
35and F<installman>. These should probably be merged. It would also be good to
36check for duplication in all the utility scripts supplied in the source
37tarball. It might be good to move them all to a subdirectory, but this would
38require careful checking to find all places that call them, and change those
39correctly.
40
0bdfc961 41=head2 common test code for timed bail out
e50bb9a1 42
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43Write portable self destruct code for tests to stop them burning CPU in
44infinite loops. This needs to avoid using alarm, as some of the tests are
45testing alarm/sleep or timers.
e50bb9a1 46
87a942b1 47=head2 POD -E<gt> HTML conversion in the core still sucks
e50bb9a1 48
938c8732 49Which is crazy given just how simple POD purports to be, and how simple HTML
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50can be. It's not actually I<as> simple as it sounds, particularly with the
51flexibility POD allows for C<=item>, but it would be good to improve the
52visual appeal of the HTML generated, and to avoid it having any validation
53errors. See also L</make HTML install work>, as the layout of installation tree
54is needed to improve the cross-linking.
938c8732 55
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56The addition of C<Pod::Simple> and its related modules may make this task
57easier to complete.
58
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59=head2 merge checkpods and podchecker
60
61F<pod/checkpods.PL> (and C<make check> in the F<pod/> subdirectory)
62implements a very basic check for pod files, but the errors it discovers
63aren't found by podchecker. Add this check to podchecker, get rid of
64checkpods and have C<make check> use podchecker.
65
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66=head2 perlmodlib.PL rewrite
67
68Currently perlmodlib.PL needs to be run from a source directory where perl
69has been built, or some modules won't be found, and others will be
70skipped. Make it run from a clean perl source tree (so it's reproducible).
71
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72=head2 Parallel testing
73
b2e2905c 74(This probably impacts much more than the core: also the Test::Harness
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75and TAP::* modules on CPAN.)
76
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77The core regression test suite is getting ever more comprehensive, which has
78the side effect that it takes longer to run. This isn't so good. Investigate
79whether it would be feasible to give the harness script the B<option> of
80running sets of tests in parallel. This would be useful for tests in
81F<t/op/*.t> and F<t/uni/*.t> and maybe some sets of tests in F<lib/>.
82
83Questions to answer
84
85=over 4
86
87=item 1
88
89How does screen layout work when you're running more than one test?
90
91=item 2
92
93How does the caller of test specify how many tests to run in parallel?
94
95=item 3
96
97How do setup/teardown tests identify themselves?
98
99=back
100
101Pugs already does parallel testing - can their approach be re-used?
102
0bdfc961 103=head2 Make Schwern poorer
e50bb9a1 104
613bd4f7 105We should have tests for everything. When all the core's modules are tested,
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106Schwern has promised to donate to $500 to TPF. We may need volunteers to
107hold him upside down and shake vigorously in order to actually extract the
108cash.
3958b146 109
0bdfc961 110=head2 Improve the coverage of the core tests
e50bb9a1 111
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112Use Devel::Cover to ascertain the core modules's test coverage, then add
113tests that are currently missing.
30222c0f 114
0bdfc961 115=head2 test B
e50bb9a1 116
0bdfc961 117A full test suite for the B module would be nice.
e50bb9a1 118
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119=head2 Deparse inlined constants
120
121Code such as this
122
123 use constant PI => 4;
124 warn PI
125
126will currently deparse as
127
128 use constant ('PI', 4);
129 warn 4;
130
131because the tokenizer inlines the value of the constant subroutine C<PI>.
132This allows various compile time optimisations, such as constant folding
133and dead code elimination. Where these haven't happened (such as the example
134above) it ought be possible to make B::Deparse work out the name of the
135original constant, because just enough information survives in the symbol
136table to do this. Specifically, the same scalar is used for the constant in
137the optree as is used for the constant subroutine, so by iterating over all
138symbol tables and generating a mapping of SV address to constant name, it
139would be possible to provide B::Deparse with this functionality.
140
0bdfc961 141=head2 A decent benchmark
e50bb9a1 142
617eabfa 143C<perlbench> seems impervious to any recent changes made to the perl core. It
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144would be useful to have a reasonable general benchmarking suite that roughly
145represented what current perl programs do, and measurably reported whether
146tweaks to the core improve, degrade or don't really affect performance, to
147guide people attempting to optimise the guts of perl. Gisle would welcome
148new tests for perlbench.
6168cf99 149
0bdfc961 150=head2 fix tainting bugs
6168cf99 151
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152Fix the bugs revealed by running the test suite with the C<-t> switch (via
153C<make test.taintwarn>).
e50bb9a1 154
0bdfc961 155=head2 Dual life everything
e50bb9a1 156
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157As part of the "dists" plan, anything that doesn't belong in the smallest perl
158distribution needs to be dual lifed. Anything else can be too. Figure out what
159changes would be needed to package that module and its tests up for CPAN, and
160do so. Test it with older perl releases, and fix the problems you find.
e50bb9a1 161
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162To make a minimal perl distribution, it's useful to look at
163F<t/lib/commonsense.t>.
164
0bdfc961 165=head2 Improving C<threads::shared>
722d2a37 166
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167Investigate whether C<threads::shared> could share aggregates properly with
168only Perl level changes to shared.pm
722d2a37 169
0bdfc961 170=head2 POSIX memory footprint
e50bb9a1 171
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172Ilya observed that use POSIX; eats memory like there's no tomorrow, and at
173various times worked to cut it down. There is probably still fat to cut out -
174for example POSIX passes Exporter some very memory hungry data structures.
e50bb9a1 175
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176=head2 embed.pl/makedef.pl
177
178There is a script F<embed.pl> that generates several header files to prefix
179all of Perl's symbols in a consistent way, to provide some semblance of
180namespace support in C<C>. Functions are declared in F<embed.fnc>, variables
907b3e23 181in F<interpvar.h>. Quite a few of the functions and variables
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182are conditionally declared there, using C<#ifdef>. However, F<embed.pl>
183doesn't understand the C macros, so the rules about which symbols are present
184when is duplicated in F<makedef.pl>. Writing things twice is bad, m'kay.
185It would be good to teach C<embed.pl> to understand the conditional
186compilation, and hence remove the duplication, and the mistakes it has caused.
e50bb9a1 187
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188=head2 use strict; and AutoLoad
189
190Currently if you write
191
192 package Whack;
193 use AutoLoader 'AUTOLOAD';
194 use strict;
195 1;
196 __END__
197 sub bloop {
198 print join (' ', No, strict, here), "!\n";
199 }
200
201then C<use strict;> isn't in force within the autoloaded subroutines. It would
202be more consistent (and less surprising) to arrange for all lexical pragmas
203in force at the __END__ block to be in force within each autoloaded subroutine.
204
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205There's a similar problem with SelfLoader.
206
0bdfc961 207=head1 Tasks that need a little sysadmin-type knowledge
e50bb9a1 208
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209Or if you prefer, tasks that you would learn from, and broaden your skills
210base...
e50bb9a1 211
cd793d32 212=head2 make HTML install work
e50bb9a1 213
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214There is an C<installhtml> target in the Makefile. It's marked as
215"experimental". It would be good to get this tested, make it work reliably, and
216remove the "experimental" tag. This would include
217
218=over 4
219
220=item 1
221
222Checking that cross linking between various parts of the documentation works.
223In particular that links work between the modules (files with POD in F<lib/>)
224and the core documentation (files in F<pod/>)
225
226=item 2
227
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228Work out how to split C<perlfunc> into chunks, preferably one per function
229group, preferably with general case code that could be used elsewhere.
230Challenges here are correctly identifying the groups of functions that go
231together, and making the right named external cross-links point to the right
232page. Things to be aware of are C<-X>, groups such as C<getpwnam> to
233C<endservent>, two or more C<=items> giving the different parameter lists, such
234as
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235
236 =item substr EXPR,OFFSET,LENGTH,REPLACEMENT
adebf063 237 =item substr EXPR,OFFSET,LENGTH
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238 =item substr EXPR,OFFSET
239
240and different parameter lists having different meanings. (eg C<select>)
241
242=back
3a89a73c 243
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244=head2 compressed man pages
245
246Be able to install them. This would probably need a configure test to see how
247the system does compressed man pages (same directory/different directory?
248same filename/different filename), as well as tweaking the F<installman> script
249to compress as necessary.
250
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251=head2 Add a code coverage target to the Makefile
252
253Make it easy for anyone to run Devel::Cover on the core's tests. The steps
254to do this manually are roughly
255
256=over 4
257
258=item *
259
260do a normal C<Configure>, but include Devel::Cover as a module to install
261(see F<INSTALL> for how to do this)
262
263=item *
264
265 make perl
266
267=item *
268
269 cd t; HARNESS_PERL_SWITCHES=-MDevel::Cover ./perl -I../lib harness
270
271=item *
272
273Process the resulting Devel::Cover database
274
275=back
276
277This just give you the coverage of the F<.pm>s. To also get the C level
278coverage you need to
279
280=over 4
281
282=item *
283
284Additionally tell C<Configure> to use the appropriate C compiler flags for
285C<gcov>
286
287=item *
288
289 make perl.gcov
290
291(instead of C<make perl>)
292
293=item *
294
295After running the tests run C<gcov> to generate all the F<.gcov> files.
296(Including down in the subdirectories of F<ext/>
297
298=item *
299
300(From the top level perl directory) run C<gcov2perl> on all the C<.gcov> files
301to get their stats into the cover_db directory.
302
303=item *
304
305Then process the Devel::Cover database
306
307=back
308
309It would be good to add a single switch to C<Configure> to specify that you
310wanted to perform perl level coverage, and another to specify C level
311coverage, and have C<Configure> and the F<Makefile> do all the right things
312automatically.
313
02f21748 314=head2 Make Config.pm cope with differences between built and installed perl
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315
316Quite often vendors ship a perl binary compiled with their (pay-for)
317compilers. People install a free compiler, such as gcc. To work out how to
318build extensions, Perl interrogates C<%Config>, so in this situation
319C<%Config> describes compilers that aren't there, and extension building
320fails. This forces people into choosing between re-compiling perl themselves
321using the compiler they have, or only using modules that the vendor ships.
322
323It would be good to find a way teach C<Config.pm> about the installation setup,
324possibly involving probing at install time or later, so that the C<%Config> in
325a binary distribution better describes the installed machine, when the
326installed machine differs from the build machine in some significant way.
327
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328=head2 linker specification files
329
330Some platforms mandate that you provide a list of a shared library's external
331symbols to the linker, so the core already has the infrastructure in place to
332do this for generating shared perl libraries. My understanding is that the
333GNU toolchain can accept an optional linker specification file, and restrict
334visibility just to symbols declared in that file. It would be good to extend
335F<makedef.pl> to support this format, and to provide a means within
336C<Configure> to enable it. This would allow Unix users to test that the
337export list is correct, and to build a perl that does not pollute the global
338namespace with private symbols.
339
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340=head2 Cross-compile support
341
342Currently C<Configure> understands C<-Dusecrosscompile> option. This option
343arranges for building C<miniperl> for TARGET machine, so this C<miniperl> is
344assumed then to be copied to TARGET machine and used as a replacement of full
345C<perl> executable.
346
d1307786 347This could be done little differently. Namely C<miniperl> should be built for
a229ae3b 348HOST and then full C<perl> with extensions should be compiled for TARGET.
d1307786 349This, however, might require extra trickery for %Config: we have one config
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350first for HOST and then another for TARGET. Tools like MakeMaker will be
351mightily confused. Having around two different types of executables and
352libraries (HOST and TARGET) makes life interesting for Makefiles and
353shell (and Perl) scripts. There is $Config{run}, normally empty, which
354can be used as an execution wrapper. Also note that in some
355cross-compilation/execution environments the HOST and the TARGET do
356not see the same filesystem(s), the $Config{run} may need to do some
357file/directory copying back and forth.
0bdfc961 358
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359=head2 roffitall
360
361Make F<pod/roffitall> be updated by F<pod/buildtoc>.
362
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363=head1 Tasks that need a little C knowledge
364
365These tasks would need a little C knowledge, but don't need any specific
366background or experience with XS, or how the Perl interpreter works
367
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368=head2 Modernize the order of directories in @INC
369
370The way @INC is laid out by default, one cannot upgrade core (dual-life)
371modules without overwriting files. This causes problems for binary
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372package builders. One possible proposal is laid out in this
373message:
374L<http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/2002-04/msg02380.html>.
fbf638cb 375
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376=head2 -Duse32bit*
377
378Natively 64-bit systems need neither -Duse64bitint nor -Duse64bitall.
379On these systems, it might be the default compilation mode, and there
380is currently no guarantee that passing no use64bitall option to the
381Configure process will build a 32bit perl. Implementing -Duse32bit*
382options would be nice for perl 5.12.
383
0bdfc961 384=head2 Make it clear from -v if this is the exact official release
89007cb3 385
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386Currently perl from C<p4>/C<rsync> ships with a F<patchlevel.h> file that
387usually defines one local patch, of the form "MAINT12345" or "RC1". The output
388of perl -v doesn't report that a perl isn't an official release, and this
89007cb3 389information can get lost in bugs reports. Because of this, the minor version
fa11829f 390isn't bumped up until RC time, to minimise the possibility of versions of perl
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391escaping that believe themselves to be newer than they actually are.
392
393It would be useful to find an elegant way to have the "this is an interim
394maintenance release" or "this is a release candidate" in the terse -v output,
395and have it so that it's easy for the pumpking to remove this just as the
396release tarball is rolled up. This way the version pulled out of rsync would
397always say "I'm a development release" and it would be safe to bump the
398reported minor version as soon as a release ships, which would aid perl
399developers.
400
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401This task is really about thinking of an elegant way to arrange the C source
402such that it's trivial for the Pumpking to flag "this is an official release"
403when making a tarball, yet leave the default source saying "I'm not the
404official release".
405
fee0a0f7 406=head2 Profile Perl - am I hot or not?
62403a3c 407
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408The Perl source code is stable enough that it makes sense to profile it,
409identify and optimise the hotspots. It would be good to measure the
410performance of the Perl interpreter using free tools such as cachegrind,
411gprof, and dtrace, and work to reduce the bottlenecks they reveal.
412
413As part of this, the idea of F<pp_hot.c> is that it contains the I<hot> ops,
414the ops that are most commonly used. The idea is that by grouping them, their
415object code will be adjacent in the executable, so they have a greater chance
416of already being in the CPU cache (or swapped in) due to being near another op
417already in use.
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418
419Except that it's not clear if these really are the most commonly used ops. So
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420as part of exercising your skills with coverage and profiling tools you might
421want to determine what ops I<really> are the most commonly used. And in turn
422suggest evictions and promotions to achieve a better F<pp_hot.c>.
62403a3c 423
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424=head2 Allocate OPs from arenas
425
426Currently all new OP structures are individually malloc()ed and free()d.
427All C<malloc> implementations have space overheads, and are now as fast as
428custom allocates so it would both use less memory and less CPU to allocate
429the various OP structures from arenas. The SV arena code can probably be
430re-used for this.
431
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432Note that Configuring perl with C<-Accflags=-DPL_OP_SLAB_ALLOC> will use
433Perl_Slab_alloc() to pack optrees into a contiguous block, which is
434probably superior to the use of OP arenas, esp. from a cache locality
435standpoint. See L<Profile Perl - am I hot or not?>.
436
a229ae3b 437=head2 Improve win32/wince.c
0bdfc961 438
a229ae3b 439Currently, numerous functions look virtually, if not completely,
02f21748 440identical in both C<win32/wince.c> and C<win32/win32.c> files, which can't
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441be good.
442
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443=head2 Use secure CRT functions when building with VC8 on Win32
444
445Visual C++ 2005 (VC++ 8.x) deprecated a number of CRT functions on the basis
446that they were "unsafe" and introduced differently named secure versions of
447them as replacements, e.g. instead of writing
448
449 FILE* f = fopen(__FILE__, "r");
450
451one should now write
452
453 FILE* f;
454 errno_t err = fopen_s(&f, __FILE__, "r");
455
456Currently, the warnings about these deprecations have been disabled by adding
457-D_CRT_SECURE_NO_DEPRECATE to the CFLAGS. It would be nice to remove that
458warning suppressant and actually make use of the new secure CRT functions.
459
460There is also a similar issue with POSIX CRT function names like fileno having
461been deprecated in favour of ISO C++ conformant names like _fileno. These
26a6faa8 462warnings are also currently suppressed by adding -D_CRT_NONSTDC_NO_DEPRECATE. It
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463might be nice to do as Microsoft suggest here too, although, unlike the secure
464functions issue, there is presumably little or no benefit in this case.
465
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466=head2 strcat(), strcpy(), strncat(), strncpy(), sprintf(), vsprintf()
467
468Maybe create a utility that checks after each libperl.a creation that
469none of the above (nor sprintf(), vsprintf(), or *SHUDDER* gets())
470ever creep back to libperl.a.
471
472 nm libperl.a | ./miniperl -alne '$o = $F[0] if /:$/; print "$o $F[1]" if $F[0] eq "U" && $F[1] =~ /^(?:strn?c(?:at|py)|v?sprintf|gets)$/'
473
474Note, of course, that this will only tell whether B<your> platform
475is using those naughty interfaces.
476
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477=head2 -D_FORTIFY_SOURCE=2, -fstack-protector
478
479Recent glibcs support C<-D_FORTIFY_SOURCE=2> and recent gcc
480(4.1 onwards?) supports C<-fstack-protector>, both of which give
481protection against various kinds of buffer overflow problems.
482These should probably be used for compiling Perl whenever available,
483Configure and/or hints files should be adjusted to probe for the
484availability of these features and enable them as appropriate.
16815324 485
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486=head1 Tasks that need a knowledge of XS
487
488These tasks would need C knowledge, and roughly the level of knowledge of
489the perl API that comes from writing modules that use XS to interface to
490C.
491
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492=head2 autovivification
493
494Make all autovivification consistent w.r.t LVALUE/RVALUE and strict/no strict;
495
496This task is incremental - even a little bit of work on it will help.
497
498=head2 Unicode in Filenames
499
500chdir, chmod, chown, chroot, exec, glob, link, lstat, mkdir, open,
501opendir, qx, readdir, readlink, rename, rmdir, stat, symlink, sysopen,
502system, truncate, unlink, utime, -X. All these could potentially accept
503Unicode filenames either as input or output (and in the case of system
504and qx Unicode in general, as input or output to/from the shell).
505Whether a filesystem - an operating system pair understands Unicode in
506filenames varies.
507
508Known combinations that have some level of understanding include
509Microsoft NTFS, Apple HFS+ (In Mac OS 9 and X) and Apple UFS (in Mac
510OS X), NFS v4 is rumored to be Unicode, and of course Plan 9. How to
511create Unicode filenames, what forms of Unicode are accepted and used
512(UCS-2, UTF-16, UTF-8), what (if any) is the normalization form used,
513and so on, varies. Finding the right level of interfacing to Perl
514requires some thought. Remember that an OS does not implicate a
515filesystem.
516
517(The Windows -C command flag "wide API support" has been at least
518temporarily retired in 5.8.1, and the -C has been repurposed, see
519L<perlrun>.)
520
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521Most probably the right way to do this would be this:
522L</"Virtualize operating system access">.
523
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524=head2 Unicode in %ENV
525
526Currently the %ENV entries are always byte strings.
87a942b1 527See L</"Virtualize operating system access">.
6d71adcd 528
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529=head2 Unicode and glob()
530
531Currently glob patterns and filenames returned from File::Glob::glob()
87a942b1 532are always byte strings. See L</"Virtualize operating system access">.
1f2e7916 533
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534=head2 Unicode and lc/uc operators
535
536Some built-in operators (C<lc>, C<uc>, etc.) behave differently, based on
537what the internal encoding of their argument is. That should not be the
538case. Maybe add a pragma to switch behaviour.
539
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540=head2 use less 'memory'
541
542Investigate trade offs to switch out perl's choices on memory usage.
543Particularly perl should be able to give memory back.
544
545This task is incremental - even a little bit of work on it will help.
546
547=head2 Re-implement C<:unique> in a way that is actually thread-safe
548
549The old implementation made bad assumptions on several levels. A good 90%
550solution might be just to make C<:unique> work to share the string buffer
551of SvPVs. That way large constant strings can be shared between ithreads,
552such as the configuration information in F<Config>.
553
554=head2 Make tainting consistent
555
556Tainting would be easier to use if it didn't take documented shortcuts and
557allow taint to "leak" everywhere within an expression.
558
559=head2 readpipe(LIST)
560
561system() accepts a LIST syntax (and a PROGRAM LIST syntax) to avoid
562running a shell. readpipe() (the function behind qx//) could be similarly
563extended.
564
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565=head2 Audit the code for destruction ordering assumptions
566
567Change 25773 notes
568
569 /* Need to check SvMAGICAL, as during global destruction it may be that
570 AvARYLEN(av) has been freed before av, and hence the SvANY() pointer
571 is now part of the linked list of SV heads, rather than pointing to
572 the original body. */
573 /* FIXME - audit the code for other bugs like this one. */
574
575adding the C<SvMAGICAL> check to
576
577 if (AvARYLEN(av) && SvMAGICAL(AvARYLEN(av))) {
578 MAGIC *mg = mg_find (AvARYLEN(av), PERL_MAGIC_arylen);
579
580Go through the core and look for similar assumptions that SVs have particular
581types, as all bets are off during global destruction.
582
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583=head2 Extend PerlIO and PerlIO::Scalar
584
585PerlIO::Scalar doesn't know how to truncate(). Implementing this
586would require extending the PerlIO vtable.
587
588Similarly the PerlIO vtable doesn't know about formats (write()), or
589about stat(), or chmod()/chown(), utime(), or flock().
590
591(For PerlIO::Scalar it's hard to see what e.g. mode bits or ownership
592would mean.)
593
594PerlIO doesn't do directories or symlinks, either: mkdir(), rmdir(),
595opendir(), closedir(), seekdir(), rewinddir(), glob(); symlink(),
596readlink().
597
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598See also L</"Virtualize operating system access">.
599
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600=head2 -C on the #! line
601
602It should be possible to make -C work correctly if found on the #! line,
603given that all perl command line options are strict ASCII, and -C changes
604only the interpretation of non-ASCII characters, and not for the script file
605handle. To make it work needs some investigation of the ordering of function
606calls during startup, and (by implication) a bit of tweaking of that order.
607
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608=head2 Propagate const outwards from Perl_moreswitches()
609
610Change 32057 changed the parameter and return value of C<Perl_moreswitches()>
611from <char *> to <const char *>. It should now be possible to propagate
612const-correctness outwards to C<S_parse_body()>, C<Perl_moreswitches()>
613and C<Perl_yylex()>.
614
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615=head2 Duplicate logic in S_method_common() and Perl_gv_fetchmethod_autoload()
616
617A comment in C<S_method_common> notes
618
619 /* This code tries to figure out just what went wrong with
620 gv_fetchmethod. It therefore needs to duplicate a lot of
621 the internals of that function. We can't move it inside
622 Perl_gv_fetchmethod_autoload(), however, since that would
623 cause UNIVERSAL->can("NoSuchPackage::foo") to croak, and we
624 don't want that.
625 */
626
627If C<Perl_gv_fetchmethod_autoload> gets rewritten to take (more) flag bits,
628then it ought to be possible to move the logic from C<S_method_common> to
629the "right" place. When making this change it would probably be good to also
630pass in at least the method name length, if not also pre-computed hash values
631when known. (I'm contemplating a plan to pre-compute hash values for common
632fixed strings such as C<ISA> and pass them in to functions.)
633
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634=head2 Organize error messages
635
636Perl's diagnostics (error messages, see L<perldiag>) could use
a8d0aeb9 637reorganizing and formalizing so that each error message has its
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638stable-for-all-eternity unique id, categorized by severity, type, and
639subsystem. (The error messages would be listed in a datafile outside
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640of the Perl source code, and the source code would only refer to the
641messages by the id.) This clean-up and regularizing should apply
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642for all croak() messages.
643
644This would enable all sorts of things: easier translation/localization
645of the messages (though please do keep in mind the caveats of
646L<Locale::Maketext> about too straightforward approaches to
647translation), filtering by severity, and instead of grepping for a
648particular error message one could look for a stable error id. (Of
649course, changing the error messages by default would break all the
650existing software depending on some particular error message...)
651
652This kind of functionality is known as I<message catalogs>. Look for
653inspiration for example in the catgets() system, possibly even use it
654if available-- but B<only> if available, all platforms will B<not>
de96509d 655have catgets().
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656
657For the really pure at heart, consider extending this item to cover
658also the warning messages (see L<perllexwarn>, C<warnings.pl>).
3236f110 659
0bdfc961 660=head1 Tasks that need a knowledge of the interpreter
3298bd4d 661
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662These tasks would need C knowledge, and knowledge of how the interpreter works,
663or a willingness to learn.
3298bd4d 664
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665=head2 lexicals used only once
666
667This warns:
668
669 $ perl -we '$pie = 42'
670 Name "main::pie" used only once: possible typo at -e line 1.
671
672This does not:
673
674 $ perl -we 'my $pie = 42'
675
676Logically all lexicals used only once should warn, if the user asks for
677warnings.
678
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679=head2 UTF-8 revamp
680
681The handling of Unicode is unclean in many places. For example, the regexp
682engine matches in Unicode semantics whenever the string or the pattern is
683flagged as UTF-8, but that should not be dependent on an internal storage
684detail of the string. Likewise, case folding behaviour is dependent on the
685UTF8 internal flag being on or off.
686
687=head2 Properly Unicode safe tokeniser and pads.
688
689The tokeniser isn't actually very UTF-8 clean. C<use utf8;> is a hack -
690variable names are stored in stashes as raw bytes, without the utf-8 flag
691set. The pad API only takes a C<char *> pointer, so that's all bytes too. The
692tokeniser ignores the UTF-8-ness of C<PL_rsfp>, or any SVs returned from
693source filters. All this could be fixed.
694
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695=head2 state variable initialization in list context
696
697Currently this is illegal:
698
699 state ($a, $b) = foo();
700
a2874905 701In Perl 6, C<state ($a) = foo();> and C<(state $a) = foo();> have different
a8d0aeb9 702semantics, which is tricky to implement in Perl 5 as currently they produce
a2874905 703the same opcode trees. The Perl 6 design is firm, so it would be good to
a8d0aeb9 704implement the necessary code in Perl 5. There are comments in
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705C<Perl_newASSIGNOP()> that show the code paths taken by various assignment
706constructions involving state variables.
636e63cb 707
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708=head2 Implement $value ~~ 0 .. $range
709
710It would be nice to extend the syntax of the C<~~> operator to also
711understand numeric (and maybe alphanumeric) ranges.
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712
713=head2 A does() built-in
714
715Like ref(), only useful. It would call the C<DOES> method on objects; it
716would also tell whether something can be dereferenced as an
717array/hash/etc., or used as a regexp, etc.
718L<http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/2007-03/msg00481.html>
719
720=head2 Tied filehandles and write() don't mix
721
722There is no method on tied filehandles to allow them to be called back by
723formats.
4fedb12c 724
d10fc472 725=head2 Attach/detach debugger from running program
1626a787 726
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727The old perltodo notes "With C<gdb>, you can attach the debugger to a running
728program if you pass the process ID. It would be good to do this with the Perl
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729debugger on a running Perl program, although I'm not sure how it would be
730done." ssh and screen do this with named pipes in /tmp. Maybe we can too.
1626a787 731
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732=head2 Optimize away empty destructors
733
734Defining an empty DESTROY method might be useful (notably in
735AUTOLOAD-enabled classes), but it's still a bit expensive to call. That
736could probably be optimized.
737
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738=head2 LVALUE functions for lists
739
740The old perltodo notes that lvalue functions don't work for list or hash
741slices. This would be good to fix.
742
743=head2 LVALUE functions in the debugger
744
745The old perltodo notes that lvalue functions don't work in the debugger. This
746would be good to fix.
747
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748=head2 regexp optimiser optional
749
750The regexp optimiser is not optional. It should configurable to be, to allow
751its performance to be measured, and its bugs to be easily demonstrated.
752
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753=head2 delete &function
754
755Allow to delete functions. One can already undef them, but they're still
756in the stash.
757
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758=head2 C</w> regex modifier
759
760That flag would enable to match whole words, and also to interpolate
761arrays as alternations. With it, C</P/w> would be roughly equivalent to:
762
763 do { local $"='|'; /\b(?:P)\b/ }
764
765See L<http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/2007-01/msg00400.html>
766for the discussion.
767
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768=head2 optional optimizer
769
770Make the peephole optimizer optional. Currently it performs two tasks as
771it walks the optree - genuine peephole optimisations, and necessary fixups of
772ops. It would be good to find an efficient way to switch out the
773optimisations whilst keeping the fixups.
774
775=head2 You WANT *how* many
776
777Currently contexts are void, scalar and list. split has a special mechanism in
778place to pass in the number of return values wanted. It would be useful to
779have a general mechanism for this, backwards compatible and little speed hit.
780This would allow proposals such as short circuiting sort to be implemented
781as a module on CPAN.
782
783=head2 lexical aliases
784
785Allow lexical aliases (maybe via the syntax C<my \$alias = \$foo>.
786
787=head2 entersub XS vs Perl
788
789At the moment pp_entersub is huge, and has code to deal with entering both
790perl and XS subroutines. Subroutine implementations rarely change between
791perl and XS at run time, so investigate using 2 ops to enter subs (one for
792XS, one for perl) and swap between if a sub is redefined.
2810d901 793
de535794 794=head2 Self-ties
2810d901 795
de535794 796Self-ties are currently illegal because they caused too many segfaults. Maybe
a8d0aeb9 797the causes of these could be tracked down and self-ties on all types
de535794 798reinstated.
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799
800=head2 Optimize away @_
801
802The old perltodo notes "Look at the "reification" code in C<av.c>".
803
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804=head2 The yada yada yada operators
805
806Perl 6's Synopsis 3 says:
807
808I<The ... operator is the "yada, yada, yada" list operator, which is used as
809the body in function prototypes. It complains bitterly (by calling fail)
810if it is ever executed. Variant ??? calls warn, and !!! calls die.>
811
812Those would be nice to add to Perl 5. That could be done without new ops.
813
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814=head2 Virtualize operating system access
815
816Implement a set of "vtables" that virtualizes operating system access
817(open(), mkdir(), unlink(), readdir(), getenv(), etc.) At the very
818least these interfaces should take SVs as "name" arguments instead of
819bare char pointers; probably the most flexible and extensible way
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820would be for the Perl-facing interfaces to accept HVs. The system
821needs to be per-operating-system and per-file-system
822hookable/filterable, preferably both from XS and Perl level
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823(L<perlport/"Files and Filesystems"> is good reading at this point,
824in fact, all of L<perlport> is.)
825
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826This has actually already been implemented (but only for Win32),
827take a look at F<iperlsys.h> and F<win32/perlhost.h>. While all Win32
828variants go through a set of "vtables" for operating system access,
829non-Win32 systems currently go straight for the POSIX/UNIX-style
830system/library call. Similar system as for Win32 should be
831implemented for all platforms. The existing Win32 implementation
832probably does not need to survive alongside this proposed new
833implementation, the approaches could be merged.
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834
835What would this give us? One often-asked-for feature this would
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836enable is using Unicode for filenames, and other "names" like %ENV,
837usernames, hostnames, and so forth.
838(See L<perlunicode/"When Unicode Does Not Happen">.)
839
840But this kind of virtualization would also allow for things like
841virtual filesystems, virtual networks, and "sandboxes" (though as long
842as dynamic loading of random object code is allowed, not very safe
843sandboxes since external code of course know not of Perl's vtables).
844An example of a smaller "sandbox" is that this feature can be used to
845implement per-thread working directories: Win32 already does this.
846
847See also L</"Extend PerlIO and PerlIO::Scalar">.
87a942b1 848
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849=head2 Investigate PADTMP hash pessimisation
850
851The peephole optimier converts constants used for hash key lookups to shared
852hash key scalars. Under ithreads, something is undoing this work. See
853See http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/2007-09/msg00793.html
854
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855=head1 Big projects
856
857Tasks that will get your name mentioned in the description of the "Highlights
87a942b1 858of 5.12"
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859
860=head2 make ithreads more robust
861
4e577f8b 862Generally make ithreads more robust. See also L</iCOW>
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863
864This task is incremental - even a little bit of work on it will help, and
865will be greatly appreciated.
866
6c047da7
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867One bit would be to write the missing code in sv.c:Perl_dirp_dup.
868
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869Fix Perl_sv_dup, et al so that threads can return objects.
870
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871=head2 iCOW
872
873Sarathy and Arthur have a proposal for an improved Copy On Write which
874specifically will be able to COW new ithreads. If this can be implemented
875it would be a good thing.
876
877=head2 (?{...}) closures in regexps
878
879Fix (or rewrite) the implementation of the C</(?{...})/> closures.
880
881=head2 A re-entrant regexp engine
882
883This will allow the use of a regex from inside (?{ }), (??{ }) and
884(?(?{ })|) constructs.
6bda09f9 885
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886=head2 Add class set operations to regexp engine
887
888Apparently these are quite useful. Anyway, Jeffery Friedl wants them.
889
890demerphq has this on his todo list, but right at the bottom.