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Porting/todo.pod: refaliasing needs fixing still
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1=head1 NAME
2
c3143508 3todo - Perl TO-DO list
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4
5=head1 DESCRIPTION
e50bb9a1 6
049aabcb 7This is a list of wishes for Perl. The most up to date version of this file
c3143508 8is at L<http://perl5.git.perl.org/perl.git/blob_plain/HEAD:/Porting/todo.pod>
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9
10The tasks we think are smaller or easier are listed first. Anyone is welcome
11to work on any of these, but it's a good idea to first contact
12I<perl5-porters@perl.org> to avoid duplication of effort, and to learn from
13any previous attempts. By all means contact a pumpking privately first if you
14prefer.
e50bb9a1 15
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16Whilst patches to make the list shorter are most welcome, ideas to add to
17the list are also encouraged. Check the perl5-porters archives for past
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18ideas, and any discussion about them. One set of archives may be found at
19L<http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/>
938c8732 20
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21What can we offer you in return? Fame, fortune, and everlasting glory? Maybe
22not, but if your patch is incorporated, then we'll add your name to the
23F<AUTHORS> file, which ships in the official distribution. How many other
24programming languages offer you 1 line of immortality?
938c8732 25
0bdfc961 26=head1 Tasks that only need Perl knowledge
e50bb9a1 27
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28=head2 Classify bug tickets by type
29
1e5abc58 30Known bugs in Perl are tracked by L<https://rt.perl.org/> (which also
aa384da9 31includes Perl 6). A summary can be found at
1e5abc58 32L<https://rt.perl.org/NoAuth/perl5/Overview.html>.
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33It shows bugs classified by "type". However, the type of many of the
34bugs is "unknown". This greatly lowers the chances of them getting
35fixed, as the number of open bugs is overwhelming -- too many to wade
36through for someone to try to find the bugs in the parts of
37Perl that s/he knows well enough to try to fix. This task involves
38going through these bugs and classifying them into one or more types.
39
40=head2 Ongoing: investigate new bug reports
41
42When a bug report is filed, it would be very helpful to have someone do
43a quick investigation to see if it is a real problem, and to reply to
44the poster about it, asking for example code that reproduces the
45problem. Such code should be added to the test suite as TODO tests, and
46the ticket should be classified by type. To get started on this task,
47look at the tickets that are marked as "New Issues" in
1e5abc58 48L<https://rt.perl.org/NoAuth/perl5/Overview.html>.
aa384da9 49
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50=head2 Migrate t/ from custom TAP generation
51
52Many tests below F<t/> still generate TAP by "hand", rather than using library
96090e4f 53functions. As explained in L<perlhack/TESTING>, tests in F<t/> are
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54written in a particular way to test that more complex constructions actually
55work before using them routinely. Hence they don't use C<Test::More>, but
56instead there is an intentionally simpler library, F<t/test.pl>. However,
57quite a few tests in F<t/> have not been refactored to use it. Refactoring
58any of these tests, one at a time, is a useful thing TODO.
59
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60The subdirectories F<base>, F<cmd>, F<comp> and F<opbasic>, that contain the
61most basic tests, should be excluded from this task.
0d8e5a42 62
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63=head2 Automate perldelta generation
64
65The perldelta file accompanying each release summaries the major changes.
66It's mostly manually generated currently, but some of that could be
67automated with a bit of perl, specifically the generation of
68
69=over
70
71=item Modules and Pragmata
72
73=item New Documentation
74
75=item New Tests
76
77=back
78
79See F<Porting/how_to_write_a_perldelta.pod> for details.
80
0bdfc961 81=head2 Make Schwern poorer
e50bb9a1 82
613bd4f7 83We should have tests for everything. When all the core's modules are tested,
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84Schwern has promised to donate to $500 to TPF. We may need volunteers to
85hold him upside down and shake vigorously in order to actually extract the
86cash.
3958b146 87
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88=head2 Write descriptions for all tests
89
90Many individual tests in the test suite lack descriptions (or names, or labels
91-- call them what you will). Many files completely lack descriptions, meaning
92that the only output you get is the test numbers. If all tests had
93descriptions, understanding what the tests are testing and why they sometimes
94fail would both get a whole lot easier.
95
0bdfc961 96=head2 Improve the coverage of the core tests
e50bb9a1 97
e1020413 98Use Devel::Cover to ascertain the core modules' test coverage, then add
02f21748 99tests that are currently missing.
30222c0f 100
0bdfc961 101=head2 test B
e50bb9a1 102
0bdfc961 103A full test suite for the B module would be nice.
e50bb9a1 104
0bdfc961 105=head2 A decent benchmark
e50bb9a1 106
617eabfa 107C<perlbench> seems impervious to any recent changes made to the perl core. It
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108would be useful to have a reasonable general benchmarking suite that roughly
109represented what current perl programs do, and measurably reported whether
110tweaks to the core improve, degrade or don't really affect performance, to
111guide people attempting to optimise the guts of perl. Gisle would welcome
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112new tests for perlbench. Steffen Schwingon would welcome help with
113L<Benchmark::Perl::Formance>
6168cf99 114
0bdfc961 115=head2 fix tainting bugs
6168cf99 116
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117Fix the bugs revealed by running the test suite with the C<-t> switch.
118Setting the TEST_ARGS environment variable to C<-taintwarn> will accomplish
119this.
e50bb9a1 120
0bdfc961 121=head2 Dual life everything
e50bb9a1 122
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123As part of the "dists" plan, anything that doesn't belong in the smallest perl
124distribution needs to be dual lifed. Anything else can be too. Figure out what
125changes would be needed to package that module and its tests up for CPAN, and
126do so. Test it with older perl releases, and fix the problems you find.
e50bb9a1 127
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128To make a minimal perl distribution, it's useful to look at
129F<t/lib/commonsense.t>.
130
0bdfc961 131=head2 POSIX memory footprint
e50bb9a1 132
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133Ilya observed that use POSIX; eats memory like there's no tomorrow, and at
134various times worked to cut it down. There is probably still fat to cut out -
135for example POSIX passes Exporter some very memory hungry data structures.
e50bb9a1 136
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137=head2 makedef.pl and conditional compilation
138
139The script F<makedef.pl> that generates the list of exported symbols on
140platforms which need this. Functions are declared in F<embed.fnc>, variables
141in F<intrpvar.h>. Quite a few of the functions and variables are conditionally
142declared there, using C<#ifdef>. However, F<makedef.pl> doesn't understand the
143C macros, so the rules about which symbols are present when is duplicated in
144the Perl code. Writing things twice is bad, m'kay. It would be good to teach
145F<.pl> to understand the conditional compilation, and hence remove the
146duplication, and the mistakes it has caused.
e50bb9a1 147
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148=head2 use strict; and AutoLoad
149
150Currently if you write
151
152 package Whack;
153 use AutoLoader 'AUTOLOAD';
154 use strict;
155 1;
156 __END__
157 sub bloop {
158 print join (' ', No, strict, here), "!\n";
159 }
160
161then C<use strict;> isn't in force within the autoloaded subroutines. It would
162be more consistent (and less surprising) to arrange for all lexical pragmas
163in force at the __END__ block to be in force within each autoloaded subroutine.
164
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165There's a similar problem with SelfLoader.
166
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167=head2 profile installman
168
169The F<installman> script is slow. All it is doing text processing, which we're
170told is something Perl is good at. So it would be nice to know what it is doing
171that is taking so much CPU, and where possible address it.
172
c69ca1d4 173=head2 enable lexical enabling/disabling of individual warnings
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174
175Currently, warnings can only be enabled or disabled by category. There
176are times when it would be useful to quash a single warning, not a
177whole category.
91d0cbf6 178
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179=head2 document diagnostics
180
181Many diagnostic messages are not currently documented. The list is at the end
182of t/porting/diag.t.
183
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184=head2 Write TODO tests for open bugs
185
186Sometimes bugs get fixed as a side effect of something else, and
187the bug remains open because no one realizes that it has been fixed.
188Ideally, every open bug should have a TODO test in the core test suite.
189
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190=head2 deparse warnings nicely
191
192Currently Deparse punts on deparsing the bitmask for warnings, which it
193dumps uglily as-is. Try running this:
194
195 $ ./perl -Ilib -MO=Deparse -e 'use warnings "pipe"; die'
196
197Deparse.pm could use the package variables in warnings.pm that warnings.pm
198itself uses to convert the list passed to it into a bitfield. Deparse just
199needs to reverse that.
200
201=head2 test and fix Deparse with perl's test suite
202
203If you run perl's tests with the TEST_ARGS environment variable set to
204C<-deparse> (e.g., run C<TEST=-deparse make test>), each test file will be
205deparsed and the deparsed output will be run. Currently there are many
206failures, which ought to be fixed. There is in F<Porting/deparse-skips.txt>
207a list of tests known to fail, but it is out of date. Updating it would
208also help.
209
210This is an incremental task. Every small bit helps. It is also a task that
211may never end. As new tests are added, they tickle corner cases that
212B::Deparse cannot yet handle correctly.
213
214This task I<may> need a bit of perl guts knowledge. But what changes need
215to be made is usually easy to see by dumping op trees with B::Concise:
216
217 $ ./perl -Ilib -MO=Concise -e 'foo(); print @_; die $$_'
218
219and adjusting B::Deparse to handle whatever you see B::Concise produce.
220This is also a good way to I<learn> how perl's op trees work.
221
0bdfc961 222=head1 Tasks that need a little sysadmin-type knowledge
e50bb9a1 223
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224Or if you prefer, tasks that you would learn from, and broaden your skills
225base...
e50bb9a1 226
cd793d32 227=head2 make HTML install work
e50bb9a1 228
78b489b0 229There is an C<install.html> target in the Makefile. It's marked as
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230"experimental". It would be good to get this tested, make it work reliably, and
231remove the "experimental" tag. This would include
232
233=over 4
234
235=item 1
236
237Checking that cross linking between various parts of the documentation works.
238In particular that links work between the modules (files with POD in F<lib/>)
239and the core documentation (files in F<pod/>)
240
241=item 2
242
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243Improving the code that split C<perlfunc> into chunks, preferably with
244general case code added to L<Pod::Functions> that could be used elsewhere.
245
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246Challenges here are correctly identifying the groups of functions that go
247together, and making the right named external cross-links point to the right
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248page. Currently this works reasonably well in the general case, and correctly
249parses two or more C<=items> giving the different parameter lists for the
250same function, such used by C<substr>. However it fails completely where
251I<different> functions are listed as a sequence of C<=items> but share the
252same description. All the functions from C<getpwnam> to C<endprotoent> have
253individual stub pages, with only the page for C<endservent> holding the
254description common to all. Likewise C<q>, C<qq> and C<qw> have stub pages,
255instead of sharing the body of C<qx>.
256
257Note also the current code isn't ideal with the two forms of C<select>, mushing
258them both into one F<select.html> with the two descriptions run together.
259Fixing this may well be a special case.
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260
261=back
3a89a73c 262
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263=head2 compressed man pages
264
265Be able to install them. This would probably need a configure test to see how
266the system does compressed man pages (same directory/different directory?
267same filename/different filename), as well as tweaking the F<installman> script
268to compress as necessary.
269
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270=head2 Add a code coverage target to the Makefile
271
272Make it easy for anyone to run Devel::Cover on the core's tests. The steps
273to do this manually are roughly
274
275=over 4
276
277=item *
278
279do a normal C<Configure>, but include Devel::Cover as a module to install
f11a3063 280(see L<INSTALL> for how to do this)
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281
282=item *
283
284 make perl
285
286=item *
287
f185f654 288 cd t; HARNESS_PERL_SWITCHES=-MDevel::Cover ./perl -I../lib harness
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289
290=item *
291
292Process the resulting Devel::Cover database
293
294=back
295
296This just give you the coverage of the F<.pm>s. To also get the C level
297coverage you need to
298
299=over 4
300
301=item *
302
303Additionally tell C<Configure> to use the appropriate C compiler flags for
304C<gcov>
305
306=item *
307
308 make perl.gcov
309
310(instead of C<make perl>)
311
312=item *
313
314After running the tests run C<gcov> to generate all the F<.gcov> files.
315(Including down in the subdirectories of F<ext/>
316
317=item *
318
319(From the top level perl directory) run C<gcov2perl> on all the C<.gcov> files
320to get their stats into the cover_db directory.
321
322=item *
323
324Then process the Devel::Cover database
325
326=back
327
328It would be good to add a single switch to C<Configure> to specify that you
329wanted to perform perl level coverage, and another to specify C level
330coverage, and have C<Configure> and the F<Makefile> do all the right things
331automatically.
332
02f21748 333=head2 Make Config.pm cope with differences between built and installed perl
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334
335Quite often vendors ship a perl binary compiled with their (pay-for)
336compilers. People install a free compiler, such as gcc. To work out how to
337build extensions, Perl interrogates C<%Config>, so in this situation
338C<%Config> describes compilers that aren't there, and extension building
339fails. This forces people into choosing between re-compiling perl themselves
340using the compiler they have, or only using modules that the vendor ships.
341
342It would be good to find a way teach C<Config.pm> about the installation setup,
343possibly involving probing at install time or later, so that the C<%Config> in
344a binary distribution better describes the installed machine, when the
345installed machine differs from the build machine in some significant way.
346
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347=head2 linker specification files
348
349Some platforms mandate that you provide a list of a shared library's external
350symbols to the linker, so the core already has the infrastructure in place to
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351do this for generating shared perl libraries. Florian Ragwitz has been working
352to offer this for the GNU toolchain, to allow Unix users to test that the
728f4ecd 353export list is correct, and to build a perl that does not pollute the global
32d539f5 354namespace with private symbols, and will fail in the same way as msvc or mingw
4e1c9055 355builds or when using PERL_DL_NONLAZY=1. See the branch smoke-me/rafl/ld_export
728f4ecd 356
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357=head2 Cross-compile support
358
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359We get requests for "how to cross compile Perl". The vast majority of these
360seem to be for a couple of scenarios:
361
362=over 4
363
364=item *
365
366Platforms that could build natively using F<./Configure> (I<e.g.> Linux or
367NetBSD on MIPS or ARM) but people want to use a beefier machine (and on the
368same OS) to build more easily.
369
370=item *
371
372Platforms that can't build natively, but no (significant) porting changes
373are needed to our current source code. Prime example of this is Android.
374
375=back
376
377There are several scripts and tools for cross-compiling perl for other
378platforms. However, these are somewhat inconsistent and scattered across the
379codebase, none are documented well, none are clearly flexible enough to
c5fb089a 380be confident that they can support any TARGET/HOST platform pair other than
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381that which they were developed on, and it's not clear how bitrotted they are.
382
383For example, C<Configure> understands C<-Dusecrosscompile> option. This option
a229ae3b 384arranges for building C<miniperl> for TARGET machine, so this C<miniperl> is
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385assumed then to be copied to TARGET machine and used as a replacement of
386full C<perl> executable. This code is almost 10 years old. Meanwhile, the
387F<Cross/> directory contains two different approaches for cross compiling to
388ARM Linux targets, relying on hand curated F<config.sh> files, but that code
389is getting on for 5 years old, and requires insider knowledge of perl's
390build system to draft a F<config.sh> for a new platform.
391
c5fb089a 392Jess Robinson has submitted a grant to TPF to work on cleaning this up.
0bdfc961 393
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394=head2 Split "linker" from "compiler"
395
396Right now, Configure probes for two commands, and sets two variables:
397
398=over 4
399
b91dd380 400=item * C<cc> (in F<cc.U>)
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401
402This variable holds the name of a command to execute a C compiler which
403can resolve multiple global references that happen to have the same
404name. Usual values are F<cc> and F<gcc>.
405Fervent ANSI compilers may be called F<c89>. AIX has F<xlc>.
406
b91dd380 407=item * C<ld> (in F<dlsrc.U>)
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408
409This variable indicates the program to be used to link
410libraries for dynamic loading. On some systems, it is F<ld>.
411On ELF systems, it should be C<$cc>. Mostly, we'll try to respect
412the hint file setting.
413
414=back
415
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416There is an implicit historical assumption from around Perl5.000alpha
417something, that C<$cc> is also the correct command for linking object files
418together to make an executable. This may be true on Unix, but it's not true
419on other platforms, and there are a maze of work arounds in other places (such
420as F<Makefile.SH>) to cope with this.
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421
422Ideally, we should create a new variable to hold the name of the executable
423linker program, probe for it in F<Configure>, and centralise all the special
424case logic there or in hints files.
425
426A small bikeshed issue remains - what to call it, given that C<$ld> is already
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427taken (arguably for the wrong thing now, but on SunOS 4.1 it is the command
428for creating dynamically-loadable modules) and C<$link> could be confused with
429the Unix command line executable of the same name, which does something
430completely different. Andy Dougherty makes the counter argument "In parrot, I
431tried to call the command used to link object files and libraries into an
432executable F<link>, since that's what my vaguely-remembered DOS and VMS
433experience suggested. I don't think any real confusion has ensued, so it's
434probably a reasonable name for perl5 to use."
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435
436"Alas, I've always worried that introducing it would make things worse,
437since now the module building utilities would have to look for
438C<$Config{link}> and institute a fall-back plan if it weren't found."
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439Although I can see that as confusing, given that C<$Config{d_link}> is true
440when (hard) links are available.
98fca0e8 441
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442=head2 Configure Windows using PowerShell
443
444Currently, Windows uses hard-coded config files based to build the
445config.h for compiling Perl. Makefiles are also hard-coded and need to be
446hand edited prior to building Perl. While this makes it easy to create a perl.exe
447that works across multiple Windows versions, being able to accurately
448configure a perl.exe for a specific Windows versions and VS C++ would be
449a nice enhancement. With PowerShell available on Windows XP and up, this
450may now be possible. Step 1 might be to investigate whether this is possible
451and use this to clean up our current makefile situation. Step 2 would be to
452see if there would be a way to use our existing metaconfig units to configure a
453Windows Perl or whether we go in a separate direction and make it so. Of
454course, we all know what step 3 is.
455
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456=head1 Tasks that need a little C knowledge
457
458These tasks would need a little C knowledge, but don't need any specific
459background or experience with XS, or how the Perl interpreter works
460
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461=head2 Weed out needless PERL_UNUSED_ARG
462
463The C code uses the macro C<PERL_UNUSED_ARG> to stop compilers warning about
464unused arguments. Often the arguments can't be removed, as there is an
465external constraint that determines the prototype of the function, so this
466approach is valid. However, there are some cases where C<PERL_UNUSED_ARG>
467could be removed. Specifically
468
469=over 4
470
471=item *
472
473The prototypes of (nearly all) static functions can be changed
474
475=item *
476
477Unused arguments generated by short cut macros are wasteful - the short cut
478macro used can be changed.
479
480=back
481
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482=head2 -Duse32bit*
483
484Natively 64-bit systems need neither -Duse64bitint nor -Duse64bitall.
485On these systems, it might be the default compilation mode, and there
486is currently no guarantee that passing no use64bitall option to the
487Configure process will build a 32bit perl. Implementing -Duse32bit*
1e2ea6fa 488options would be nice for perl 5.25.2.
bcbaa2d5 489
fee0a0f7 490=head2 Profile Perl - am I hot or not?
62403a3c 491
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492The Perl source code is stable enough that it makes sense to profile it,
493identify and optimise the hotspots. It would be good to measure the
494performance of the Perl interpreter using free tools such as cachegrind,
495gprof, and dtrace, and work to reduce the bottlenecks they reveal.
496
497As part of this, the idea of F<pp_hot.c> is that it contains the I<hot> ops,
498the ops that are most commonly used. The idea is that by grouping them, their
499object code will be adjacent in the executable, so they have a greater chance
500of already being in the CPU cache (or swapped in) due to being near another op
501already in use.
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502
503Except that it's not clear if these really are the most commonly used ops. So
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504as part of exercising your skills with coverage and profiling tools you might
505want to determine what ops I<really> are the most commonly used. And in turn
506suggest evictions and promotions to achieve a better F<pp_hot.c>.
62403a3c 507
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508One piece of Perl code that might make a good testbed is F<installman>.
509
a229ae3b 510=head2 Improve win32/wince.c
0bdfc961 511
a229ae3b 512Currently, numerous functions look virtually, if not completely,
c23989d1 513identical in both F<win32/wince.c> and F<win32/win32.c> files, which can't
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514be good.
515
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516=head2 Use secure CRT functions when building with VC8 on Win32
517
518Visual C++ 2005 (VC++ 8.x) deprecated a number of CRT functions on the basis
519that they were "unsafe" and introduced differently named secure versions of
520them as replacements, e.g. instead of writing
521
522 FILE* f = fopen(__FILE__, "r");
523
524one should now write
525
526 FILE* f;
527 errno_t err = fopen_s(&f, __FILE__, "r");
528
529Currently, the warnings about these deprecations have been disabled by adding
530-D_CRT_SECURE_NO_DEPRECATE to the CFLAGS. It would be nice to remove that
531warning suppressant and actually make use of the new secure CRT functions.
532
533There is also a similar issue with POSIX CRT function names like fileno having
534been deprecated in favour of ISO C++ conformant names like _fileno. These
26a6faa8 535warnings are also currently suppressed by adding -D_CRT_NONSTDC_NO_DEPRECATE. It
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536might be nice to do as Microsoft suggest here too, although, unlike the secure
537functions issue, there is presumably little or no benefit in this case.
538
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539=head2 Fix POSIX::access() and chdir() on Win32
540
541These functions currently take no account of DACLs and therefore do not behave
542correctly in situations where access is restricted by DACLs (as opposed to the
543read-only attribute).
544
545Furthermore, POSIX::access() behaves differently for directories having the
546read-only attribute set depending on what CRT library is being used. For
547example, the _access() function in the VC6 and VC7 CRTs (wrongly) claim that
548such directories are not writable, whereas in fact all directories are writable
549unless access is denied by DACLs. (In the case of directories, the read-only
550attribute actually only means that the directory cannot be deleted.) This CRT
551bug is fixed in the VC8 and VC9 CRTs (but, of course, the directory may still
552not actually be writable if access is indeed denied by DACLs).
553
554For the chdir() issue, see ActiveState bug #74552:
b4af8972 555L<http://bugs.activestate.com/show_bug.cgi?id=74552>
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556
557Therefore, DACLs should be checked both for consistency across CRTs and for
558the correct answer.
559
560(Note that perl's -w operator should not be modified to check DACLs. It has
561been written so that it reflects the state of the read-only attribute, even
562for directories (whatever CRT is being used), for symmetry with chmod().)
563
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564=head2 Arenas for GPs? For MAGIC?
565
566C<struct gp> and C<struct magic> are both currently allocated by C<malloc>.
567It might be a speed or memory saving to change to using arenas. Or it might
568not. It would need some suitable benchmarking first. In particular, C<GP>s
569can probably be changed with minimal compatibility impact (probably nothing
570outside of the core, or even outside of F<gv.c> allocates them), but they
571probably aren't allocated/deallocated often enough for a speed saving. Whereas
572C<MAGIC> is allocated/deallocated more often, but in turn, is also something
573more externally visible, so changing the rules here may bite external code.
574
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575=head2 Shared arenas
576
577Several SV body structs are now the same size, notably PVMG and PVGV, PVAV and
578PVHV, and PVCV and PVFM. It should be possible to allocate and return same
579sized bodies from the same actual arena, rather than maintaining one arena for
580each. This could save 4-6K per thread, of memory no longer tied up in the
581not-yet-allocated part of an arena.
582
8964cfe0 583
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584=head1 Tasks that need a knowledge of XS
585
586These tasks would need C knowledge, and roughly the level of knowledge of
587the perl API that comes from writing modules that use XS to interface to
588C.
589
e851c105
DG
590=head2 Write an XS cookbook
591
592Create pod/perlxscookbook.pod with short, task-focused 'recipes' in XS that
593demonstrate common tasks and good practices. (Some of these might be
594extracted from perlguts.) The target audience should be XS novices, who need
595more examples than perlguts but something less overwhelming than perlapi.
596Recipes should provide "one pretty good way to do it" instead of TIMTOWTDI.
597
5b7d14ff
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598Rather than focusing on interfacing Perl to C libraries, such a cookbook
599should probably focus on how to optimize Perl routines by re-writing them
600in XS. This will likely be more motivating to those who mostly work in
601Perl but are looking to take the next step into XS.
602
603Deconstructing and explaining some simpler XS modules could be one way to
604bootstrap a cookbook. (List::Util? Class::XSAccessor? Tree::Ternary_XS?)
605Another option could be deconstructing the implementation of some simpler
606functions in op.c.
607
0b162fb0 608=head2 Document how XSUBs can use C<cv_set_call_checker> to inline themselves as OPs
05fb4e20
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609
610For a simple XSUB, often the subroutine dispatch takes more time than the
0b162fb0
NC
611XSUB itself. v5.14.0 now allows XSUBs to register a function which will be
612called when the parser is finished building an C<entersub> op which calls
613them.
614
615Registration is done with C<Perl_cv_set_call_checker>, is documented at the
616API level in L<perlapi>, and L<perl5140delta/Custom per-subroutine check hooks>
617notes that it can be used to inline a subroutine, by replacing it with a
618custom op. However there is no further detail of the code needed to do this.
619It would be useful to add one or more annotated examples of how to create
620XSUBs that inline.
621
622This should provide a measurable speed up to simple XSUBs inside
05fb4e20
NC
623tight loops. Initially one would have to write the OP alternative
624implementation by hand, but it's likely that this should be reasonably
625straightforward for the type of XSUB that would benefit the most. Longer
626term, once the run-time implementation is proven, it should be possible to
627progressively update ExtUtils::ParseXS to generate OP implementations for
628some XSUBs.
629
1ab33739
FC
630=head2 Document how XS modules can install lexical subs
631
632There is an example in XS::APItest (look for C<lexical_import> in
633F<ext/XS-APItest/APItest.xs>). The documentation could be based on it.
634
318bf708
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635=head2 Remove the use of SVs as temporaries in dump.c
636
637F<dump.c> contains debugging routines to dump out the contains of perl data
638structures, such as C<SV>s, C<AV>s and C<HV>s. Currently, the dumping code
639B<uses> C<SV>s for its temporary buffers, which was a logical initial
640implementation choice, as they provide ready made memory handling.
641
642However, they also lead to a lot of confusion when it happens that what you're
643trying to debug is seen by the code in F<dump.c>, correctly or incorrectly, as
644a temporary scalar it can use for a temporary buffer. It's also not possible
645to dump scalars before the interpreter is properly set up, such as during
646ithreads cloning. It would be good to progressively replace the use of scalars
647as string accumulation buffers with something much simpler, directly allocated
648by C<malloc>. The F<dump.c> code is (or should be) only producing 7 bit
649US-ASCII, so output character sets are not an issue.
650
651Producing and proving an internal simple buffer allocation would make it easier
652to re-write the internals of the PerlIO subsystem to avoid using C<SV>s for
653B<its> buffers, use of which can cause problems similar to those of F<dump.c>,
654at similar times.
655
5d96f598
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656=head2 safely supporting POSIX SA_SIGINFO
657
658Some years ago Jarkko supplied patches to provide support for the POSIX
659SA_SIGINFO feature in Perl, passing the extra data to the Perl signal handler.
660
661Unfortunately, it only works with "unsafe" signals, because under safe
662signals, by the time Perl gets to run the signal handler, the extra
663information has been lost. Moreover, it's not easy to store it somewhere,
664as you can't call mutexs, or do anything else fancy, from inside a signal
665handler.
666
667So it strikes me that we could provide safe SA_SIGINFO support
668
669=over 4
670
671=item 1
672
673Provide global variables for two file descriptors
674
675=item 2
676
677When the first request is made via C<sigaction> for C<SA_SIGINFO>, create a
678pipe, store the reader in one, the writer in the other
679
680=item 3
681
682In the "safe" signal handler (C<Perl_csighandler()>/C<S_raise_signal()>), if
683the C<siginfo_t> pointer non-C<NULL>, and the writer file handle is open,
684
685=over 8
686
687=item 1
688
689serialise signal number, C<struct siginfo_t> (or at least the parts we care
690about) into a small auto char buff
691
692=item 2
693
694C<write()> that (non-blocking) to the writer fd
695
696=over 12
697
698=item 1
699
700if it writes 100%, flag the signal in a counter of "signals on the pipe" akin
701to the current per-signal-number counts
702
703=item 2
704
705if it writes 0%, assume the pipe is full. Flag the data as lost?
706
707=item 3
708
709if it writes partially, croak a panic, as your OS is broken.
710
711=back
712
713=back
714
715=item 4
716
717in the regular C<PERL_ASYNC_CHECK()> processing, if there are "signals on
718the pipe", read the data out, deserialise, build the Perl structures on
719the stack (code in C<Perl_sighandler()>, the "unsafe" handler), and call as
720usual.
721
722=back
723
724I think that this gets us decent C<SA_SIGINFO> support, without the current risk
725of running Perl code inside the signal handler context. (With all the dangers
726of things like C<malloc> corruption that that currently offers us)
727
728For more information see the thread starting with this message:
b4af8972 729L<http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/2008-03/msg00305.html>
5d96f598 730
6d71adcd
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731=head2 autovivification
732
733Make all autovivification consistent w.r.t LVALUE/RVALUE and strict/no strict;
734
735This task is incremental - even a little bit of work on it will help.
736
737=head2 Unicode in Filenames
738
739chdir, chmod, chown, chroot, exec, glob, link, lstat, mkdir, open,
740opendir, qx, readdir, readlink, rename, rmdir, stat, symlink, sysopen,
741system, truncate, unlink, utime, -X. All these could potentially accept
742Unicode filenames either as input or output (and in the case of system
743and qx Unicode in general, as input or output to/from the shell).
744Whether a filesystem - an operating system pair understands Unicode in
745filenames varies.
746
747Known combinations that have some level of understanding include
748Microsoft NTFS, Apple HFS+ (In Mac OS 9 and X) and Apple UFS (in Mac
749OS X), NFS v4 is rumored to be Unicode, and of course Plan 9. How to
750create Unicode filenames, what forms of Unicode are accepted and used
751(UCS-2, UTF-16, UTF-8), what (if any) is the normalization form used,
752and so on, varies. Finding the right level of interfacing to Perl
753requires some thought. Remember that an OS does not implicate a
754filesystem.
755
756(The Windows -C command flag "wide API support" has been at least
757temporarily retired in 5.8.1, and the -C has been repurposed, see
758L<perlrun>.)
759
87a942b1
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760Most probably the right way to do this would be this:
761L</"Virtualize operating system access">.
762
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763=head2 Unicode in %ENV
764
765Currently the %ENV entries are always byte strings.
87a942b1 766See L</"Virtualize operating system access">.
6d71adcd 767
799c141b
SH
768(See RT ticket #113536 for information on Win32's handling of %ENV,
769which was fixed to work with native ANSI codepage characters in the
770environment, but still doesn't work with other characters outside of
771that codepage present in the environment.)
772
1f2e7916
JD
773=head2 Unicode and glob()
774
775Currently glob patterns and filenames returned from File::Glob::glob()
87a942b1 776are always byte strings. See L</"Virtualize operating system access">.
1f2e7916 777
6d71adcd
NC
778=head2 use less 'memory'
779
780Investigate trade offs to switch out perl's choices on memory usage.
781Particularly perl should be able to give memory back.
782
783This task is incremental - even a little bit of work on it will help.
784
785=head2 Re-implement C<:unique> in a way that is actually thread-safe
786
787The old implementation made bad assumptions on several levels. A good 90%
788solution might be just to make C<:unique> work to share the string buffer
789of SvPVs. That way large constant strings can be shared between ithreads,
790such as the configuration information in F<Config>.
791
792=head2 Make tainting consistent
793
794Tainting would be easier to use if it didn't take documented shortcuts and
795allow taint to "leak" everywhere within an expression.
796
797=head2 readpipe(LIST)
798
799system() accepts a LIST syntax (and a PROGRAM LIST syntax) to avoid
800running a shell. readpipe() (the function behind qx//) could be similarly
3b17061e
FC
801extended. Note that changing readpipe() itself may not be the solution, as
802it currently has unary precedence, and allowing a list would change the
803precedence.
6d71adcd 804
6d71adcd
NC
805=head2 Audit the code for destruction ordering assumptions
806
807Change 25773 notes
808
f185f654
KW
809 /* Need to check SvMAGICAL, as during global destruction it may be that
810 AvARYLEN(av) has been freed before av, and hence the SvANY() pointer
811 is now part of the linked list of SV heads, rather than pointing to
812 the original body. */
813 /* FIXME - audit the code for other bugs like this one. */
6d71adcd
NC
814
815adding the C<SvMAGICAL> check to
816
817 if (AvARYLEN(av) && SvMAGICAL(AvARYLEN(av))) {
818 MAGIC *mg = mg_find (AvARYLEN(av), PERL_MAGIC_arylen);
819
820Go through the core and look for similar assumptions that SVs have particular
821types, as all bets are off during global destruction.
822
749904bf
JH
823=head2 Extend PerlIO and PerlIO::Scalar
824
825PerlIO::Scalar doesn't know how to truncate(). Implementing this
826would require extending the PerlIO vtable.
827
828Similarly the PerlIO vtable doesn't know about formats (write()), or
829about stat(), or chmod()/chown(), utime(), or flock().
830
831(For PerlIO::Scalar it's hard to see what e.g. mode bits or ownership
832would mean.)
833
834PerlIO doesn't do directories or symlinks, either: mkdir(), rmdir(),
835opendir(), closedir(), seekdir(), rewinddir(), glob(); symlink(),
836readlink().
837
94da6c29
JH
838See also L</"Virtualize operating system access">.
839
d6c1e11f
JH
840=head2 Organize error messages
841
842Perl's diagnostics (error messages, see L<perldiag>) could use
a8d0aeb9 843reorganizing and formalizing so that each error message has its
d6c1e11f
JH
844stable-for-all-eternity unique id, categorized by severity, type, and
845subsystem. (The error messages would be listed in a datafile outside
c4bd451b
CB
846of the Perl source code, and the source code would only refer to the
847messages by the id.) This clean-up and regularizing should apply
d6c1e11f
JH
848for all croak() messages.
849
850This would enable all sorts of things: easier translation/localization
851of the messages (though please do keep in mind the caveats of
852L<Locale::Maketext> about too straightforward approaches to
853translation), filtering by severity, and instead of grepping for a
854particular error message one could look for a stable error id. (Of
855course, changing the error messages by default would break all the
856existing software depending on some particular error message...)
857
858This kind of functionality is known as I<message catalogs>. Look for
859inspiration for example in the catgets() system, possibly even use it
860if available-- but B<only> if available, all platforms will B<not>
de96509d 861have catgets().
d6c1e11f
JH
862
863For the really pure at heart, consider extending this item to cover
47a9c258 864also the warning messages (see L<warnings>, F<regen/warnings.pl>).
3236f110 865
0bdfc961 866=head1 Tasks that need a knowledge of the interpreter
3298bd4d 867
0bdfc961
NC
868These tasks would need C knowledge, and knowledge of how the interpreter works,
869or a willingness to learn.
3298bd4d 870
514e62e3
FC
871=head2 fix refaliasing with nested and recursive subroutines
872
873Currently aliasing lexical variables via reference only applies to the
874current subroutine, and does not propagate to inner closures, nor does
875aliasing of outer variables within closures propagate to the outer
876subroutine. This is because each subroutine has its own lexical pad and the
877aliasing works by changing which SV the pad points to.
878
879One possible way to fix this would be to create new ops for accessing
880variables that are closed over. So C<my $x; sub {$x}> would use a new op
881type, say C<padoutsv>, instead of the C<padsv> currently used in the
882sub. That new op would possibly check a flag or some such and see if it
883needs to fetch the variable from an outer pad. If we follow this approach,
884it should be possible at compile time to detect cases where the more
885complex C<padoutsv> op is unnecessary and revert back to the simpler,
886faster C<padsv>. There would need to be corresponding ops for arrays,
887hashes, and subs, too.
888
889There is also a related issue with recursion and C<state> variables. A
890subroutine actually has a list of lexical pads, each one used at a
891different recursion level. If a C<state> variable is aliased to another
892variable after a recursive call to the same subroutine, that higher call
893depth will not see the effect of aliasing, because the second pad will have
894been created already. Similarly, aliasing a state variable within a
895recursive call will not affect outer calls, even though all call depths are
896supposed to share the same C<state> variables.
897
898Both of these bugs affect C<foreach> aliasing, too.
899
10517af5
JD
900=head2 forbid labels with keyword names
901
902Currently C<goto keyword> "computes" the label value:
903
904 $ perl -e 'goto print'
905 Can't find label 1 at -e line 1.
906
343c8006
JD
907It is controversial if the right way to avoid the confusion is to forbid
908labels with keyword names, or if it would be better to always treat
909bareword expressions after a "goto" as a label and never as a keyword.
10517af5 910
de6375e3
RGS
911=head2 truncate() prototype
912
913The prototype of truncate() is currently C<$$>. It should probably
f3fccad6 914be C<*$> instead. (This is changed in F<regen/opcodes>.)
de6375e3 915
565590b5
NC
916=head2 error reporting of [$a ; $b]
917
918Using C<;> inside brackets is a syntax error, and we don't propose to change
919that by giving it any meaning. However, it's not reported very helpfully:
920
921 $ perl -e '$a = [$b; $c];'
922 syntax error at -e line 1, near "$b;"
923 syntax error at -e line 1, near "$c]"
924 Execution of -e aborted due to compilation errors.
925
926It should be possible to hook into the tokeniser or the lexer, so that when a
927C<;> is parsed where it is not legal as a statement terminator (ie inside
928C<{}> used as a hashref, C<[]> or C<()>) it issues an error something like
929I<';' isn't legal inside an expression - if you need multiple statements use a
930do {...} block>. See the thread starting at
b4af8972 931L<http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/2008-09/msg00573.html>
565590b5 932
e053a921
RS
933=head2 strict as warnings
934
b8b41556 935See L<http://markmail.org/message/vbrupaslr3bybmvk>, where Joshua ben Jore
e053a921
RS
936writes: I've been of the opinion that everything strict.pm does ought to be
937able to considered just warnings that have been promoted to 'FATAL'.
938
718140ec
NC
939=head2 lexicals used only once
940
941This warns:
942
943 $ perl -we '$pie = 42'
944 Name "main::pie" used only once: possible typo at -e line 1.
945
946This does not:
947
948 $ perl -we 'my $pie = 42'
949
950Logically all lexicals used only once should warn, if the user asks for
d6f4ea2e
SP
951warnings. An unworked RT ticket (#5087) has been open for almost seven
952years for this discrepancy.
718140ec 953
a3d15f9a
RGS
954=head2 UTF-8 revamp
955
85c006b6
KW
956The handling of Unicode is unclean in many places. In the regex engine
957there are especially many problems. The swash data structure could be
958replaced my something better. Inversion lists and maps are likely
959candidates. The whole Unicode database could be placed in-core for a
960huge speed-up. Only minimal work was done on the optimizer when utf8
961was added, with the result that the synthetic start class often will
962fail to narrow down the possible choices when given non-Latin1 input.
4e1c9055 963Karl Williamson has been working on this - talk to him.
a3d15f9a 964
636e63cb
NC
965=head2 state variable initialization in list context
966
967Currently this is illegal:
968
969 state ($a, $b) = foo();
970
a2874905 971In Perl 6, C<state ($a) = foo();> and C<(state $a) = foo();> have different
a8d0aeb9 972semantics, which is tricky to implement in Perl 5 as currently they produce
a2874905 973the same opcode trees. The Perl 6 design is firm, so it would be good to
a8d0aeb9 974implement the necessary code in Perl 5. There are comments in
a2874905
NC
975C<Perl_newASSIGNOP()> that show the code paths taken by various assignment
976constructions involving state variables.
636e63cb 977
a393eb28
RGS
978=head2 A does() built-in
979
980Like ref(), only useful. It would call the C<DOES> method on objects; it
981would also tell whether something can be dereferenced as an
982array/hash/etc., or used as a regexp, etc.
983L<http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/2007-03/msg00481.html>
984
985=head2 Tied filehandles and write() don't mix
986
987There is no method on tied filehandles to allow them to be called back by
988formats.
4fedb12c 989
53967bb9
RGS
990=head2 Propagate compilation hints to the debugger
991
992Currently a debugger started with -dE on the command-line doesn't see the
993features enabled by -E. More generally hints (C<$^H> and C<%^H>) aren't
994propagated to the debugger. Probably it would be a good thing to propagate
995hints from the innermost non-C<DB::> scope: this would make code eval'ed
996in the debugger see the features (and strictures, etc.) currently in
997scope.
998
d10fc472 999=head2 Attach/detach debugger from running program
1626a787 1000
cd793d32
NC
1001The old perltodo notes "With C<gdb>, you can attach the debugger to a running
1002program if you pass the process ID. It would be good to do this with the Perl
0bdfc961
NC
1003debugger on a running Perl program, although I'm not sure how it would be
1004done." ssh and screen do this with named pipes in /tmp. Maybe we can too.
1626a787 1005
c5fb089a 1006=head2 regexp optimizer optional
0bdfc961 1007
c5fb089a
DS
1008The regexp optimizer is not optional. It should be configurable to be optional
1009and to allow its performance to be measured and its bugs to be easily
1010demonstrated.
0bdfc961 1011
ef36c6a7
RGS
1012=head2 C</w> regex modifier
1013
1014That flag would enable to match whole words, and also to interpolate
1015arrays as alternations. With it, C</P/w> would be roughly equivalent to:
1016
1017 do { local $"='|'; /\b(?:P)\b/ }
1018
b4af8972
RB
1019See
1020L<http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/2007-01/msg00400.html>
ef36c6a7
RGS
1021for the discussion.
1022
0bdfc961
NC
1023=head2 optional optimizer
1024
1025Make the peephole optimizer optional. Currently it performs two tasks as
1026it walks the optree - genuine peephole optimisations, and necessary fixups of
1027ops. It would be good to find an efficient way to switch out the
1028optimisations whilst keeping the fixups.
1029
1030=head2 You WANT *how* many
1031
1032Currently contexts are void, scalar and list. split has a special mechanism in
1033place to pass in the number of return values wanted. It would be useful to
1034have a general mechanism for this, backwards compatible and little speed hit.
1035This would allow proposals such as short circuiting sort to be implemented
1036as a module on CPAN.
1037
de535794 1038=head2 Self-ties
2810d901 1039
de535794 1040Self-ties are currently illegal because they caused too many segfaults. Maybe
a8d0aeb9 1041the causes of these could be tracked down and self-ties on all types
de535794 1042reinstated.
0bdfc961
NC
1043
1044=head2 Optimize away @_
1045
1046The old perltodo notes "Look at the "reification" code in C<av.c>".
1047
87a942b1
JH
1048=head2 Virtualize operating system access
1049
1050Implement a set of "vtables" that virtualizes operating system access
9fe0b8be
RS
1051(chdir(), chmod(), dbmopen(), getenv(), glob(), link(), mkdir(), open(),
1052opendir(), readdir(), rename(), rmdir(), stat(), sysopen(), uname(),
1053unlink(), etc.) At the very least these interfaces should take SVs as
1054"name" arguments instead of bare char pointers; probably the most
1055flexible and extensible way would be for the Perl-facing interfaces to
1056accept HVs. The system needs to be per-operating-system and
1057per-file-system hookable/filterable, preferably both from XS and Perl
1058level (L<perlport/"Files and Filesystems"> is good reading at this
1059point, in fact, all of L<perlport> is.)
87a942b1 1060
e1a3d5d1
JH
1061This has actually already been implemented (but only for Win32),
1062take a look at F<iperlsys.h> and F<win32/perlhost.h>. While all Win32
1063variants go through a set of "vtables" for operating system access,
e1020413 1064non-Win32 systems currently go straight for the POSIX/Unix-style
e1a3d5d1
JH
1065system/library call. Similar system as for Win32 should be
1066implemented for all platforms. The existing Win32 implementation
1067probably does not need to survive alongside this proposed new
1068implementation, the approaches could be merged.
87a942b1
JH
1069
1070What would this give us? One often-asked-for feature this would
94da6c29
JH
1071enable is using Unicode for filenames, and other "names" like %ENV,
1072usernames, hostnames, and so forth.
1073(See L<perlunicode/"When Unicode Does Not Happen">.)
1074
1075But this kind of virtualization would also allow for things like
1076virtual filesystems, virtual networks, and "sandboxes" (though as long
1077as dynamic loading of random object code is allowed, not very safe
1078sandboxes since external code of course know not of Perl's vtables).
1079An example of a smaller "sandbox" is that this feature can be used to
1080implement per-thread working directories: Win32 already does this.
1081
1082See also L</"Extend PerlIO and PerlIO::Scalar">.
87a942b1 1083
52960e22
JC
1084=head2 repack the optree
1085
af4a745c
FC
1086B<Note:> This entry was written in reference to the I<old> slab allocator,
1087removed in commit 7aef8e5bd14.
1088
52960e22 1089Repacking the optree after execution order is determined could allow
057163d7 1090removal of NULL ops, and optimal ordering of OPs with respect to cache-line
2723c0fb 1091filling. I think that
057163d7
NC
1092the best way to do this is to make it an optional step just before the
1093completed optree is attached to anything else, and to use the slab allocator
2723c0fb
FC
1094unchanged--but allocate a single slab the right size, avoiding partial
1095slabs--, so that freeing ops is identical whether or not this step runs.
057163d7
NC
1096Note that the slab allocator allocates ops downwards in memory, so one would
1097have to actually "allocate" the ops in reverse-execution order to get them
1098contiguous in memory in execution order.
1099
b4af8972
RB
1100See
1101L<http://www.nntp.perl.org/group/perl.perl5.porters/2007/12/msg131975.html>
057163d7
NC
1102
1103Note that running this copy, and then freeing all the old location ops would
1104cause their slabs to be freed, which would eliminate possible memory wastage if
1105the previous suggestion is implemented, and we swap slabs more frequently.
52960e22 1106
12e06b6f
NC
1107=head2 eliminate incorrect line numbers in warnings
1108
1109This code
1110
1111 use warnings;
1112 my $undef;
f703fc96 1113
12e06b6f
NC
1114 if ($undef == 3) {
1115 } elsif ($undef == 0) {
1116 }
1117
18a16cc5 1118used to produce this output:
12e06b6f
NC
1119
1120 Use of uninitialized value in numeric eq (==) at wrong.pl line 4.
1121 Use of uninitialized value in numeric eq (==) at wrong.pl line 4.
1122
18a16cc5
NC
1123where the line of the second warning was misreported - it should be line 5.
1124Rafael fixed this - the problem arose because there was no nextstate OP
1125between the execution of the C<if> and the C<elsif>, hence C<PL_curcop> still
1126reports that the currently executing line is line 4. The solution was to inject
1127a nextstate OPs for each C<elsif>, although it turned out that the nextstate
1128OP needed to be a nulled OP, rather than a live nextstate OP, else other line
1129numbers became misreported. (Jenga!)
12e06b6f
NC
1130
1131The problem is more general than C<elsif> (although the C<elsif> case is the
1132most common and the most confusing). Ideally this code
1133
1134 use warnings;
1135 my $undef;
f703fc96 1136
12e06b6f
NC
1137 my $a = $undef + 1;
1138 my $b
1139 = $undef
1140 + 1;
1141
1142would produce this output
1143
f185f654
KW
1144 Use of uninitialized value $undef in addition (+) at wrong.pl line 4.
1145 Use of uninitialized value $undef in addition (+) at wrong.pl line 7.
12e06b6f
NC
1146
1147(rather than lines 4 and 5), but this would seem to require every OP to carry
1148(at least) line number information.
1149
1150What might work is to have an optional line number in memory just before the
1151BASEOP structure, with a flag bit in the op to say whether it's present.
1152Initially during compile every OP would carry its line number. Then add a late
c5fb089a 1153pass to the optimizer (potentially combined with L</repack the optree>) which
12e06b6f
NC
1154looks at the two ops on every edge of the graph of the execution path. If
1155the line number changes, flags the destination OP with this information.
1156Once all paths are traced, replace every op with the flag with a
1157nextstate-light op (that just updates C<PL_curcop>), which in turn then passes
1158control on to the true op. All ops would then be replaced by variants that
1159do not store the line number. (Which, logically, why it would work best in
1160conjunction with L</repack the optree>, as that is already copying/reallocating
1161all the OPs)
1162
18a16cc5
NC
1163(Although I should note that we're not certain that doing this for the general
1164case is worth it)
1165
52960e22
JC
1166=head2 optimize tail-calls
1167
1168Tail-calls present an opportunity for broadly applicable optimization;
1169anywhere that C<< return foo(...) >> is called, the outer return can
1170be replaced by a goto, and foo will return directly to the outer
1171caller, saving (conservatively) 25% of perl's call&return cost, which
1172is relatively higher than in C. The scheme language is known to do
1173this heavily. B::Concise provides good insight into where this
1174optimization is possible, ie anywhere entersub,leavesub op-sequence
1175occurs.
1176
1177 perl -MO=Concise,-exec,a,b,-main -e 'sub a{ 1 }; sub b {a()}; b(2)'
1178
1179Bottom line on this is probably a new pp_tailcall function which
1180combines the code in pp_entersub, pp_leavesub. This should probably
1181be done 1st in XS, and using B::Generate to patch the new OP into the
1182optrees.
1183
e12cb30b 1184=head2 Add C<0odddd>
0c397127
KW
1185
1186It has been proposed that octal constants be specifiable through the syntax
1187C<0oddddd>, parallel to the existing construct to specify hex constants
1188C<0xddddd>
1189
bf7d9bd8
AC
1190=head2 Revisit the regex super-linear cache code
1191
1192Perl executes regexes using the traditional backtracking algorithm, which
1193makes it possible to implement a variety of powerful pattern-matching
1194features (like embedded code blocks), at the cost of taking exponential time
1195to run on some pathological patterns. The exponential-time problem is
1196mitigated by the I<super-linear cache>, which detects when we're processing
1197such a pathological pattern, and does some additional bookkeeping to avoid
1198much of the work. However, that code has bit-rotted a little; some patterns
1199don't make as much use of it as they should. The proposal is to analyse
1200where the current cache code has problems, and extend it to cover those cases.
1201
1202See also
1203L<http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/2013-01/msg00339.html>
1204
0bdfc961
NC
1205=head1 Big projects
1206
1207Tasks that will get your name mentioned in the description of the "Highlights
1e2ea6fa 1208of 5.25.2"
0bdfc961
NC
1209
1210=head2 make ithreads more robust
1211
45a81a90 1212Generally make ithreads more robust.
0bdfc961
NC
1213
1214This task is incremental - even a little bit of work on it will help, and
1215will be greatly appreciated.
1216
07577ec1
FC
1217One bit would be to determine how to clone directory handles on systems
1218without a C<fchdir> function (in sv.c:Perl_dirp_dup).
6c047da7 1219
59c7f7d5
RGS
1220Fix Perl_sv_dup, et al so that threads can return objects.
1221
44a7a252
JV
1222=head1 Tasks for microperl
1223
1224
1225[ Each and every one of these may be obsolete, but they were listed
1226 in the old Todo.micro file]
1227
44a7a252
JV
1228=head2 do away with fork/exec/wait?
1229
1230(system, popen should be enough?)
1231
1232=head2 some of the uconfig.sh really needs to be probed (using cc) in buildtime:
1233
1234(uConfigure? :-) native datatype widths and endianness come to mind
1235