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Add Rafael's 5.10 roadmap to perltodo.
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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
4e577f8b 23=head1 The roadmap to 5.10
938c8732 24
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25The roadmap to 5.10 envisages feature based releases, as various items in this
26TODO are completed.
27
28=head2 Needed for a 5.9.3 release
29
30=over
31
32=item *
33Implement L</lexical pragmas>
34
35=back
36
37=head2 Needed for a 5.9.4 release
38
39=over
40
41=item *
42Review assertions. Review syntax to combine assertions. Can assertions take
43advantage of the lexical pragams work? L</What hooks would assertions need?>
44
45=back
46
47=head2 Needed for a 5.9.5 release
48
49=over
50
51=item *
52Implement L</_ prototype character>
53
54=item *
55Implement L</state variables>
56
57=back
58
59=head2 Needed for a 5.9.6 release
60
61Stabilisation. If all goes well, this will be the equivalent of a 5.10-beta.
e50bb9a1 62
0bdfc961 63=head1 Tasks that only need Perl knowledge
e50bb9a1 64
0bdfc961 65=head2 common test code for timed bail out
e50bb9a1 66
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67Write portable self destruct code for tests to stop them burning CPU in
68infinite loops. This needs to avoid using alarm, as some of the tests are
69testing alarm/sleep or timers.
e50bb9a1 70
0bdfc961 71=head2 POD -> HTML conversion in the core still sucks
e50bb9a1 72
938c8732 73Which is crazy given just how simple POD purports to be, and how simple HTML
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74can be. It's not actually I<as> simple as it sounds, particularly with the
75flexibility POD allows for C<=item>, but it would be good to improve the
76visual appeal of the HTML generated, and to avoid it having any validation
77errors. See also L</make HTML install work>, as the layout of installation tree
78is needed to improve the cross-linking.
938c8732 79
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80=head2 Parallel testing
81
82The core regression test suite is getting ever more comprehensive, which has
83the side effect that it takes longer to run. This isn't so good. Investigate
84whether it would be feasible to give the harness script the B<option> of
85running sets of tests in parallel. This would be useful for tests in
86F<t/op/*.t> and F<t/uni/*.t> and maybe some sets of tests in F<lib/>.
87
88Questions to answer
89
90=over 4
91
92=item 1
93
94How does screen layout work when you're running more than one test?
95
96=item 2
97
98How does the caller of test specify how many tests to run in parallel?
99
100=item 3
101
102How do setup/teardown tests identify themselves?
103
104=back
105
106Pugs already does parallel testing - can their approach be re-used?
107
0bdfc961 108=head2 Make Schwern poorer
e50bb9a1 109
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110We should have for everything. When all the core's modules are tested,
111Schwern has promised to donate to $500 to TPF. We may need volunteers to
112hold him upside down and shake vigorously in order to actually extract the
113cash.
3958b146 114
0bdfc961 115See F<t/lib/1_compile.t> for the 3 remaining modules that need tests.
e50bb9a1 116
0bdfc961 117=head2 Improve the coverage of the core tests
e50bb9a1 118
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119Use Devel::Cover to ascertain the core's test coverage, then add tests that
120are currently missing.
30222c0f 121
0bdfc961 122=head2 test B
e50bb9a1 123
0bdfc961 124A full test suite for the B module would be nice.
e50bb9a1 125
0bdfc961 126=head2 A decent benchmark
e50bb9a1 127
617eabfa 128C<perlbench> seems impervious to any recent changes made to the perl core. It
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129would be useful to have a reasonable general benchmarking suite that roughly
130represented what current perl programs do, and measurably reported whether
131tweaks to the core improve, degrade or don't really affect performance, to
132guide people attempting to optimise the guts of perl. Gisle would welcome
133new tests for perlbench.
6168cf99 134
0bdfc961 135=head2 fix tainting bugs
6168cf99 136
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137Fix the bugs revealed by running the test suite with the C<-t> switch (via
138C<make test.taintwarn>).
e50bb9a1 139
0bdfc961 140=head2 Dual life everything
e50bb9a1 141
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142As part of the "dists" plan, anything that doesn't belong in the smallest perl
143distribution needs to be dual lifed. Anything else can be too. Figure out what
144changes would be needed to package that module and its tests up for CPAN, and
145do so. Test it with older perl releases, and fix the problems you find.
e50bb9a1 146
0bdfc961 147=head2 Improving C<threads::shared>
722d2a37 148
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149Investigate whether C<threads::shared> could share aggregates properly with
150only Perl level changes to shared.pm
722d2a37 151
0bdfc961 152=head2 POSIX memory footprint
e50bb9a1 153
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154Ilya observed that use POSIX; eats memory like there's no tomorrow, and at
155various times worked to cut it down. There is probably still fat to cut out -
156for example POSIX passes Exporter some very memory hungry data structures.
e50bb9a1 157
e50bb9a1 158
e50bb9a1 159
e50bb9a1 160
e50bb9a1 161
adebf063 162
adebf063 163
0bdfc961 164=head1 Tasks that need a little sysadmin-type knowledge
e50bb9a1 165
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166Or if you prefer, tasks that you would learn from, and broaden your skills
167base...
e50bb9a1 168
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169=head2 Relocatable perl
170
171The C level patches needed to create a relocatable perl binary are done, as
172is the work on F<Config.pm>. All that's left to do is the C<Configure> tweaking
173to let people specify how they want to do the install.
174
cd793d32 175=head2 make HTML install work
e50bb9a1 176
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177There is an C<installhtml> target in the Makefile. It's marked as
178"experimental". It would be good to get this tested, make it work reliably, and
179remove the "experimental" tag. This would include
180
181=over 4
182
183=item 1
184
185Checking that cross linking between various parts of the documentation works.
186In particular that links work between the modules (files with POD in F<lib/>)
187and the core documentation (files in F<pod/>)
188
189=item 2
190
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191Work out how to split C<perlfunc> into chunks, preferably one per function
192group, preferably with general case code that could be used elsewhere.
193Challenges here are correctly identifying the groups of functions that go
194together, and making the right named external cross-links point to the right
195page. Things to be aware of are C<-X>, groups such as C<getpwnam> to
196C<endservent>, two or more C<=items> giving the different parameter lists, such
197as
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198
199 =item substr EXPR,OFFSET,LENGTH,REPLACEMENT
200
201 =item substr EXPR,OFFSET,LENGTH
202
203 =item substr EXPR,OFFSET
204
205and different parameter lists having different meanings. (eg C<select>)
206
207=back
3a89a73c 208
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209=head2 compressed man pages
210
211Be able to install them. This would probably need a configure test to see how
212the system does compressed man pages (same directory/different directory?
213same filename/different filename), as well as tweaking the F<installman> script
214to compress as necessary.
215
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216=head2 Add a code coverage target to the Makefile
217
218Make it easy for anyone to run Devel::Cover on the core's tests. The steps
219to do this manually are roughly
220
221=over 4
222
223=item *
224
225do a normal C<Configure>, but include Devel::Cover as a module to install
226(see F<INSTALL> for how to do this)
227
228=item *
229
230 make perl
231
232=item *
233
234 cd t; HARNESS_PERL_SWITCHES=-MDevel::Cover ./perl -I../lib harness
235
236=item *
237
238Process the resulting Devel::Cover database
239
240=back
241
242This just give you the coverage of the F<.pm>s. To also get the C level
243coverage you need to
244
245=over 4
246
247=item *
248
249Additionally tell C<Configure> to use the appropriate C compiler flags for
250C<gcov>
251
252=item *
253
254 make perl.gcov
255
256(instead of C<make perl>)
257
258=item *
259
260After running the tests run C<gcov> to generate all the F<.gcov> files.
261(Including down in the subdirectories of F<ext/>
262
263=item *
264
265(From the top level perl directory) run C<gcov2perl> on all the C<.gcov> files
266to get their stats into the cover_db directory.
267
268=item *
269
270Then process the Devel::Cover database
271
272=back
273
274It would be good to add a single switch to C<Configure> to specify that you
275wanted to perform perl level coverage, and another to specify C level
276coverage, and have C<Configure> and the F<Makefile> do all the right things
277automatically.
278
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279=head2 Make Config.pm cope with differences between build and installed perl
280
281Quite often vendors ship a perl binary compiled with their (pay-for)
282compilers. People install a free compiler, such as gcc. To work out how to
283build extensions, Perl interrogates C<%Config>, so in this situation
284C<%Config> describes compilers that aren't there, and extension building
285fails. This forces people into choosing between re-compiling perl themselves
286using the compiler they have, or only using modules that the vendor ships.
287
288It would be good to find a way teach C<Config.pm> about the installation setup,
289possibly involving probing at install time or later, so that the C<%Config> in
290a binary distribution better describes the installed machine, when the
291installed machine differs from the build machine in some significant way.
292
46925299 293=head2 make parallel builds work
0bdfc961 294
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295Currently parallel builds (such as C<make -j3>) don't work reliably. We believe
296that this is due to incomplete dependency specification in the F<Makefile>.
297It would be good if someone were able to track down the causes of these
298problems, so that parallel builds worked properly.
0bdfc961 299
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300=head2 linker specification files
301
302Some platforms mandate that you provide a list of a shared library's external
303symbols to the linker, so the core already has the infrastructure in place to
304do this for generating shared perl libraries. My understanding is that the
305GNU toolchain can accept an optional linker specification file, and restrict
306visibility just to symbols declared in that file. It would be good to extend
307F<makedef.pl> to support this format, and to provide a means within
308C<Configure> to enable it. This would allow Unix users to test that the
309export list is correct, and to build a perl that does not pollute the global
310namespace with private symbols.
311
8523e164 312
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313
314
315=head1 Tasks that need a little C knowledge
316
317These tasks would need a little C knowledge, but don't need any specific
318background or experience with XS, or how the Perl interpreter works
319
320=head2 Make it clear from -v if this is the exact official release
89007cb3 321
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322Currently perl from C<p4>/C<rsync> ships with a F<patchlevel.h> file that
323usually defines one local patch, of the form "MAINT12345" or "RC1". The output
324of perl -v doesn't report that a perl isn't an official release, and this
89007cb3 325information can get lost in bugs reports. Because of this, the minor version
fa11829f 326isn't bumped up until RC time, to minimise the possibility of versions of perl
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327escaping that believe themselves to be newer than they actually are.
328
329It would be useful to find an elegant way to have the "this is an interim
330maintenance release" or "this is a release candidate" in the terse -v output,
331and have it so that it's easy for the pumpking to remove this just as the
332release tarball is rolled up. This way the version pulled out of rsync would
333always say "I'm a development release" and it would be safe to bump the
334reported minor version as soon as a release ships, which would aid perl
335developers.
336
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337This task is really about thinking of an elegant way to arrange the C source
338such that it's trivial for the Pumpking to flag "this is an official release"
339when making a tarball, yet leave the default source saying "I'm not the
340official release".
341
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342=head2 Tidy up global variables
343
344There's a note in F<intrpvar.h>
345
346 /* These two variables are needed to preserve 5.8.x bincompat because
347 we can't change function prototypes of two exported functions.
348 Probably should be taken out of blead soon, and relevant prototypes
349 changed. */
350
351So doing this, and removing any of the unused variables still present would
352be good.
353
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354=head2 Ordering of "global" variables.
355
356F<thrdvar.h> and F<intrpvarh> define the "global" variables that need to be
357per-thread under ithreads, where the variables are actually elements in a
358structure. As C dictates, the variables must be laid out in order of
359declaration. There is a comment
360C</* Important ones in the first cache line (if alignment is done right) */>
361which implies that at some point in the past the ordering was carefully chosen
362(at least in part). However, it's clear that the ordering is less than perfect,
363as currently there are things such as 7 C<bool>s in a row, then something
364typically requiring 4 byte alignment, and then an odd C<bool> later on.
365(C<bool>s are typically defined as C<char>s). So it would be good for someone
366to review the ordering of the variables, to see how much alignment padding can
367be removed.
368
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369=head2 bincompat functions
370
371There are lots of functions which are retained for binary compatibility.
372Clean these up. Move them to mathom.c, and don't compile for blead?
373
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374=head2 am I hot or not?
375
376The idea of F<pp_hot.c> is that it contains the I<hot> ops, the ops that are
377most commonly used. The idea is that by grouping them, their object code will
378be adjacent in the executable, so they have a greater chance of already being
379in the CPU cache (or swapped in) due to being near another op already in use.
380
381Except that it's not clear if these really are the most commonly used ops. So
382anyone feeling like exercising their skill with coverage and profiling tools
383might want to determine what ops I<really> are the most commonly used. And in
384turn suggest evictions and promotions to achieve a better F<pp_hot.c>.
385
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386=head2 emulate the per-thread memory pool on Unix
387
388For Windows, ithreads allocates memory for each thread from a separate pool,
389which it discards at thread exit. It also checks that memory is free()d to
390the correct pool. Neither check is done on Unix, so code developed there won't
391be subject to such strictures, so can harbour bugs that only show up when the
392code reaches Windows.
393
394It would be good to be able to optionally emulate the Window pool system on
395Unix, to let developers who only have access to Unix, or want to use
396Unix-specific debugging tools, check for these problems. To do this would
397involve figuring out how the C<PerlMem_*> macros wrap C<malloc()> access, and
398providing a layer that records/checks the identity of the thread making the
399call, and recording all the memory allocated by each thread via this API so
400that it can be summarily free()d at thread exit. One implementation idea
401would be to increase the size of allocation, and store the C<my_perl> pointer
402(to identify the thread) at the start, along with pointers to make a linked
403list of blocks for this thread. To avoid alignment problems it would be
404necessary to do something like
405
406 union memory_header_padded {
407 struct memory_header {
408 void *thread_id; /* For my_perl */
409 void *next; /* Pointer to next block for this thread */
410 } data;
411 long double padding; /* whatever type has maximal alignment constraint */
412 };
413
414
415although C<long double> might not be the only type to add to the padding
416union.
62403a3c 417
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418=head2 reduce duplication in sv_setsv_flags
419
420C<Perl_sv_setsv_flags> has a comment
421C</* There's a lot of redundancy below but we're going for speed here */>
422
423Whilst this was true 10 years ago, the growing disparity between RAM and CPU
424speeds mean that the trade offs have changed. In addition, the duplicate code
425adds to the maintenance burden. It would be good to see how much of the
426redundancy can be pruned, particular in the less common paths. (Profiling
427tools at the ready...). For example, why does the test for
428"Can't redefine active sort subroutine" need to occur in two places?
429
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430
431
432
0bdfc961 433=head1 Tasks that need a knowledge of XS
e50bb9a1 434
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435These tasks would need C knowledge, and roughly the level of knowledge of
436the perl API that comes from writing modules that use XS to interface to
437C.
438
439=head2 IPv6
440
441Clean this up. Check everything in core works
442
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443=head2 shrink C<GV>s, C<CV>s
444
445By removing unused elements and careful re-ordering, the structures for C<AV>s
446and C<HV>s have recently been shrunk considerably. It's probable that the same
447approach would find savings in C<GV>s and C<CV>s, if not all the other
448larger-than-C<PVMG> types.
449
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450=head2 merge Perl_sv_2[inpu]v
451
452There's a lot of code shared between C<Perl_sv_2iv_flags>,
453C<Perl_sv_2uv_flags>, C<Perl_sv_2nv>, and C<Perl_sv_2pv_flags>. It would be
454interesting to see if some of it can be merged into common shared static
455functions. In particular, C<Perl_sv_2uv_flags> started out as a cut&paste
456from C<Perl_sv_2iv_flags> around 5.005_50 time, and it may be possible to
457replace both with a single function that returns a value or union which is
458split out by the macros in F<sv.h>
459
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460=head2 UTF8 caching code
461
462The string position/offset cache is not optional. It should be.
463
464=head2 Implicit Latin 1 => Unicode translation
465
466Conversions from byte strings to UTF-8 currently map high bit characters
467to Unicode without translation (or, depending on how you look at it, by
468implicitly assuming that the byte strings are in Latin-1). As perl assumes
469the C locale by default, upgrading a string to UTF-8 may change the
470meaning of its contents regarding character classes, case mapping, etc.
471This should probably emit a warning (at least).
472
473This task is incremental - even a little bit of work on it will help.
e50bb9a1 474
cd793d32 475=head2 autovivification
e50bb9a1 476
cd793d32 477Make all autovivification consistent w.r.t LVALUE/RVALUE and strict/no strict;
e50bb9a1 478
0bdfc961 479This task is incremental - even a little bit of work on it will help.
e50bb9a1 480
0bdfc961 481=head2 Unicode in Filenames
e50bb9a1 482
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483chdir, chmod, chown, chroot, exec, glob, link, lstat, mkdir, open,
484opendir, qx, readdir, readlink, rename, rmdir, stat, symlink, sysopen,
485system, truncate, unlink, utime, -X. All these could potentially accept
486Unicode filenames either as input or output (and in the case of system
487and qx Unicode in general, as input or output to/from the shell).
488Whether a filesystem - an operating system pair understands Unicode in
489filenames varies.
e50bb9a1 490
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491Known combinations that have some level of understanding include
492Microsoft NTFS, Apple HFS+ (In Mac OS 9 and X) and Apple UFS (in Mac
493OS X), NFS v4 is rumored to be Unicode, and of course Plan 9. How to
494create Unicode filenames, what forms of Unicode are accepted and used
495(UCS-2, UTF-16, UTF-8), what (if any) is the normalization form used,
496and so on, varies. Finding the right level of interfacing to Perl
497requires some thought. Remember that an OS does not implicate a
498filesystem.
e50bb9a1 499
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500(The Windows -C command flag "wide API support" has been at least
501temporarily retired in 5.8.1, and the -C has been repurposed, see
502L<perlrun>.)
969e704b 503
0bdfc961 504=head2 Unicode in %ENV
969e704b 505
0bdfc961 506Currently the %ENV entries are always byte strings.
e50bb9a1 507
0bdfc961 508=head2 use less 'memory'
e50bb9a1 509
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510Investigate trade offs to switch out perl's choices on memory usage.
511Particularly perl should be able to give memory back.
e50bb9a1 512
0bdfc961 513This task is incremental - even a little bit of work on it will help.
0abe3f7c 514
0bdfc961 515=head2 Re-implement C<:unique> in a way that is actually thread-safe
0abe3f7c 516
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517The old implementation made bad assumptions on several levels. A good 90%
518solution might be just to make C<:unique> work to share the string buffer
519of SvPVs. That way large constant strings can be shared between ithreads,
520such as the configuration information in F<Config>.
0abe3f7c 521
0bdfc961 522=head2 Make tainting consistent
0abe3f7c 523
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524Tainting would be easier to use if it didn't take documented shortcuts and
525allow taint to "leak" everywhere within an expression.
0abe3f7c 526
0bdfc961 527=head2 readpipe(LIST)
0abe3f7c 528
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529system() accepts a LIST syntax (and a PROGRAM LIST syntax) to avoid
530running a shell. readpipe() (the function behind qx//) could be similarly
531extended.
0abe3f7c 532
e50bb9a1 533
e50bb9a1 534
e50bb9a1 535
f86a8bc5 536
0bdfc961 537=head1 Tasks that need a knowledge of the interpreter
3298bd4d 538
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539These tasks would need C knowledge, and knowledge of how the interpreter works,
540or a willingness to learn.
3298bd4d 541
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542=head2 lexical pragmas
543
544Reimplement the mechanism of lexical pragmas to be more extensible. Fix
545current pragmas that don't work well (or at all) with lexical scopes or in
546run-time eval(STRING) (C<sort>, C<re>, C<encoding> for example). MJD has a
547preliminary patch that implements this.
0562c0e3 548
d10fc472 549=head2 Attach/detach debugger from running program
1626a787 550
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551The old perltodo notes "With C<gdb>, you can attach the debugger to a running
552program if you pass the process ID. It would be good to do this with the Perl
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553debugger on a running Perl program, although I'm not sure how it would be
554done." ssh and screen do this with named pipes in /tmp. Maybe we can too.
1626a787 555
0bdfc961 556=head2 inlining autoloaded constants
d10fc472 557
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558Currently the optimiser can inline constants when expressed as subroutines
559with prototype ($) that return a constant. Likewise, many packages wrapping
560C libraries export lots of constants as subroutines which are AUTOLOADed on
561demand. However, these have no prototypes, so can't be seen as constants by
562the optimiser. Some way of cheaply (low syntax, low memory overhead) to the
563perl compiler that a name is a constant would be great, so that it knows to
564call the AUTOLOAD routine at compile time, and then inline the constant.
80b46460 565
0bdfc961 566=head2 Constant folding
80b46460 567
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568The peephole optimiser should trap errors during constant folding, and give
569up on the folding, rather than bailing out at compile time. It is quite
570possible that the unfoldable constant is in unreachable code, eg something
571akin to C<$a = 0/0 if 0;>
572
573=head2 LVALUE functions for lists
574
575The old perltodo notes that lvalue functions don't work for list or hash
576slices. This would be good to fix.
577
578=head2 LVALUE functions in the debugger
579
580The old perltodo notes that lvalue functions don't work in the debugger. This
581would be good to fix.
582
583=head2 _ prototype character
584
585Study the possibility of adding a new prototype character, C<_>, meaning
586"this argument defaults to $_".
587
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588=head2 state variables
589
590C<my $foo if 0;> is deprecated, and should be replaced with
591C<state $x = "initial value\n";> the syntax from Perl 6.
592
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593=head2 @INC source filter to Filter::Simple
594
595The second return value from a sub in @INC can be a source filter. This isn't
596documented. It should be changed to use Filter::Simple, tested and documented.
597
598=head2 regexp optimiser optional
599
600The regexp optimiser is not optional. It should configurable to be, to allow
601its performance to be measured, and its bugs to be easily demonstrated.
602
603=head2 UNITCHECK
604
605Introduce a new special block, UNITCHECK, which is run at the end of a
606compilation unit (module, file, eval(STRING) block). This will correspond to
607the Perl 6 CHECK. Perl 5's CHECK cannot be changed or removed because the
608O.pm/B.pm backend framework depends on it.
609
610=head2 optional optimizer
611
612Make the peephole optimizer optional. Currently it performs two tasks as
613it walks the optree - genuine peephole optimisations, and necessary fixups of
614ops. It would be good to find an efficient way to switch out the
615optimisations whilst keeping the fixups.
616
617=head2 You WANT *how* many
618
619Currently contexts are void, scalar and list. split has a special mechanism in
620place to pass in the number of return values wanted. It would be useful to
621have a general mechanism for this, backwards compatible and little speed hit.
622This would allow proposals such as short circuiting sort to be implemented
623as a module on CPAN.
624
625=head2 lexical aliases
626
627Allow lexical aliases (maybe via the syntax C<my \$alias = \$foo>.
628
629=head2 entersub XS vs Perl
630
631At the moment pp_entersub is huge, and has code to deal with entering both
632perl and XS subroutines. Subroutine implementations rarely change between
633perl and XS at run time, so investigate using 2 ops to enter subs (one for
634XS, one for perl) and swap between if a sub is redefined.
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635
636=head2 Self ties
637
638self ties are currently illegal because they caused too many segfaults. Maybe
639the causes of these could be tracked down and self-ties on all types re-
640instated.
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641
642=head2 Optimize away @_
643
644The old perltodo notes "Look at the "reification" code in C<av.c>".
645
646=head2 switch ops
647
648The old perltodo notes "Although we have C<Switch.pm> in core, Larry points to
649the dormant C<nswitch> and C<cswitch> ops in F<pp.c>; using these opcodes would
650be much faster."
651
652=head2 What hooks would assertions need?
653
654Assertions are in the core, and work. However, assertions needed to be added
655as a core patch, rather than an XS module in ext, or a CPAN module, because
656the core has no hooks in the necessary places. It would be useful to
657investigate what hooks would need to be added to make it possible to provide
658the full assertion support from a CPAN module, so that we aren't constraining
659the imagination of future CPAN authors.
660
661
662
663
664
665
666
667=head1 Big projects
668
669Tasks that will get your name mentioned in the description of the "Highlights
670of 5.10"
671
672=head2 make ithreads more robust
673
4e577f8b 674Generally make ithreads more robust. See also L</iCOW>
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675
676This task is incremental - even a little bit of work on it will help, and
677will be greatly appreciated.
678
679=head2 iCOW
680
681Sarathy and Arthur have a proposal for an improved Copy On Write which
682specifically will be able to COW new ithreads. If this can be implemented
683it would be a good thing.
684
685=head2 (?{...}) closures in regexps
686
687Fix (or rewrite) the implementation of the C</(?{...})/> closures.
688
689=head2 A re-entrant regexp engine
690
691This will allow the use of a regex from inside (?{ }), (??{ }) and
692(?(?{ })|) constructs.