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7711098a GS |
1 | =head1 NAME |
2 | ||
c3143508 | 3 | todo - Perl TO-DO list |
7711098a GS |
4 | |
5 | =head1 DESCRIPTION | |
e50bb9a1 | 6 | |
049aabcb | 7 | This is a list of wishes for Perl. The most up to date version of this file |
c3143508 | 8 | is at L<http://perl5.git.perl.org/perl.git/blob_plain/HEAD:/Porting/todo.pod> |
049aabcb NC |
9 | |
10 | The tasks we think are smaller or easier are listed first. Anyone is welcome | |
11 | to work on any of these, but it's a good idea to first contact | |
12 | I<perl5-porters@perl.org> to avoid duplication of effort, and to learn from | |
13 | any previous attempts. By all means contact a pumpking privately first if you | |
14 | prefer. | |
e50bb9a1 | 15 | |
0bdfc961 NC |
16 | Whilst patches to make the list shorter are most welcome, ideas to add to |
17 | the list are also encouraged. Check the perl5-porters archives for past | |
b4af8972 RB |
18 | ideas, and any discussion about them. One set of archives may be found at |
19 | L<http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/> | |
938c8732 | 20 | |
617eabfa NC |
21 | What can we offer you in return? Fame, fortune, and everlasting glory? Maybe |
22 | not, but if your patch is incorporated, then we'll add your name to the | |
23 | F<AUTHORS> file, which ships in the official distribution. How many other | |
24 | programming languages offer you 1 line of immortality? | |
938c8732 | 25 | |
0bdfc961 | 26 | =head1 Tasks that only need Perl knowledge |
e50bb9a1 | 27 | |
de2b17d8 NC |
28 | =head2 Migrate t/ from custom TAP generation |
29 | ||
30 | Many tests below F<t/> still generate TAP by "hand", rather than using library | |
96090e4f | 31 | functions. As explained in L<perlhack/TESTING>, tests in F<t/> are |
de2b17d8 NC |
32 | written in a particular way to test that more complex constructions actually |
33 | work before using them routinely. Hence they don't use C<Test::More>, but | |
34 | instead there is an intentionally simpler library, F<t/test.pl>. However, | |
35 | quite a few tests in F<t/> have not been refactored to use it. Refactoring | |
36 | any of these tests, one at a time, is a useful thing TODO. | |
37 | ||
0d8e5a42 RGS |
38 | The subdirectories F<base>, F<cmd> and F<comp>, that contain the most |
39 | basic tests, should be excluded from this task. | |
40 | ||
0be987a2 NC |
41 | =head2 Automate perldelta generation |
42 | ||
43 | The perldelta file accompanying each release summaries the major changes. | |
44 | It's mostly manually generated currently, but some of that could be | |
45 | automated with a bit of perl, specifically the generation of | |
46 | ||
47 | =over | |
48 | ||
49 | =item Modules and Pragmata | |
50 | ||
51 | =item New Documentation | |
52 | ||
53 | =item New Tests | |
54 | ||
55 | =back | |
56 | ||
57 | See F<Porting/how_to_write_a_perldelta.pod> for details. | |
58 | ||
0bdfc961 | 59 | =head2 Make Schwern poorer |
e50bb9a1 | 60 | |
613bd4f7 | 61 | We should have tests for everything. When all the core's modules are tested, |
0bdfc961 NC |
62 | Schwern has promised to donate to $500 to TPF. We may need volunteers to |
63 | hold him upside down and shake vigorously in order to actually extract the | |
64 | cash. | |
3958b146 | 65 | |
831efc5a JK |
66 | =head2 Write descriptions for all tests |
67 | ||
68 | Many individual tests in the test suite lack descriptions (or names, or labels | |
69 | -- call them what you will). Many files completely lack descriptions, meaning | |
70 | that the only output you get is the test numbers. If all tests had | |
71 | descriptions, understanding what the tests are testing and why they sometimes | |
72 | fail would both get a whole lot easier. | |
73 | ||
0bdfc961 | 74 | =head2 Improve the coverage of the core tests |
e50bb9a1 | 75 | |
e1020413 | 76 | Use Devel::Cover to ascertain the core modules' test coverage, then add |
02f21748 | 77 | tests that are currently missing. |
30222c0f | 78 | |
0bdfc961 | 79 | =head2 test B |
e50bb9a1 | 80 | |
0bdfc961 | 81 | A full test suite for the B module would be nice. |
e50bb9a1 | 82 | |
0bdfc961 | 83 | =head2 A decent benchmark |
e50bb9a1 | 84 | |
617eabfa | 85 | C<perlbench> seems impervious to any recent changes made to the perl core. It |
0bdfc961 NC |
86 | would be useful to have a reasonable general benchmarking suite that roughly |
87 | represented what current perl programs do, and measurably reported whether | |
88 | tweaks to the core improve, degrade or don't really affect performance, to | |
89 | guide people attempting to optimise the guts of perl. Gisle would welcome | |
4e1c9055 NC |
90 | new tests for perlbench. Steffen Schwingon would welcome help with |
91 | L<Benchmark::Perl::Formance> | |
6168cf99 | 92 | |
0bdfc961 | 93 | =head2 fix tainting bugs |
6168cf99 | 94 | |
0bdfc961 NC |
95 | Fix the bugs revealed by running the test suite with the C<-t> switch (via |
96 | C<make test.taintwarn>). | |
e50bb9a1 | 97 | |
0bdfc961 | 98 | =head2 Dual life everything |
e50bb9a1 | 99 | |
0bdfc961 NC |
100 | As part of the "dists" plan, anything that doesn't belong in the smallest perl |
101 | distribution needs to be dual lifed. Anything else can be too. Figure out what | |
102 | changes would be needed to package that module and its tests up for CPAN, and | |
103 | do so. Test it with older perl releases, and fix the problems you find. | |
e50bb9a1 | 104 | |
a393eb28 RGS |
105 | To make a minimal perl distribution, it's useful to look at |
106 | F<t/lib/commonsense.t>. | |
107 | ||
0bdfc961 | 108 | =head2 POSIX memory footprint |
e50bb9a1 | 109 | |
0bdfc961 NC |
110 | Ilya observed that use POSIX; eats memory like there's no tomorrow, and at |
111 | various times worked to cut it down. There is probably still fat to cut out - | |
112 | for example POSIX passes Exporter some very memory hungry data structures. | |
e50bb9a1 | 113 | |
8c422da5 NC |
114 | =head2 makedef.pl and conditional compilation |
115 | ||
116 | The script F<makedef.pl> that generates the list of exported symbols on | |
117 | platforms which need this. Functions are declared in F<embed.fnc>, variables | |
118 | in F<intrpvar.h>. Quite a few of the functions and variables are conditionally | |
119 | declared there, using C<#ifdef>. However, F<makedef.pl> doesn't understand the | |
120 | C macros, so the rules about which symbols are present when is duplicated in | |
121 | the Perl code. Writing things twice is bad, m'kay. It would be good to teach | |
122 | F<.pl> to understand the conditional compilation, and hence remove the | |
123 | duplication, and the mistakes it has caused. | |
e50bb9a1 | 124 | |
801de10e NC |
125 | =head2 use strict; and AutoLoad |
126 | ||
127 | Currently if you write | |
128 | ||
129 | package Whack; | |
130 | use AutoLoader 'AUTOLOAD'; | |
131 | use strict; | |
132 | 1; | |
133 | __END__ | |
134 | sub bloop { | |
135 | print join (' ', No, strict, here), "!\n"; | |
136 | } | |
137 | ||
138 | then C<use strict;> isn't in force within the autoloaded subroutines. It would | |
139 | be more consistent (and less surprising) to arrange for all lexical pragmas | |
140 | in force at the __END__ block to be in force within each autoloaded subroutine. | |
141 | ||
773b3597 RGS |
142 | There's a similar problem with SelfLoader. |
143 | ||
91d0cbf6 NC |
144 | =head2 profile installman |
145 | ||
146 | The F<installman> script is slow. All it is doing text processing, which we're | |
147 | told is something Perl is good at. So it would be nice to know what it is doing | |
148 | that is taking so much CPU, and where possible address it. | |
149 | ||
c69ca1d4 | 150 | =head2 enable lexical enabling/disabling of individual warnings |
a9ed9b74 JV |
151 | |
152 | Currently, warnings can only be enabled or disabled by category. There | |
153 | are times when it would be useful to quash a single warning, not a | |
154 | whole category. | |
91d0cbf6 | 155 | |
85234543 KW |
156 | =head2 document diagnostics |
157 | ||
158 | Many diagnostic messages are not currently documented. The list is at the end | |
159 | of t/porting/diag.t. | |
160 | ||
0bdfc961 | 161 | =head1 Tasks that need a little sysadmin-type knowledge |
e50bb9a1 | 162 | |
0bdfc961 NC |
163 | Or if you prefer, tasks that you would learn from, and broaden your skills |
164 | base... | |
e50bb9a1 | 165 | |
cd793d32 | 166 | =head2 make HTML install work |
e50bb9a1 | 167 | |
78b489b0 | 168 | There is an C<install.html> target in the Makefile. It's marked as |
adebf063 NC |
169 | "experimental". It would be good to get this tested, make it work reliably, and |
170 | remove the "experimental" tag. This would include | |
171 | ||
172 | =over 4 | |
173 | ||
174 | =item 1 | |
175 | ||
176 | Checking that cross linking between various parts of the documentation works. | |
177 | In particular that links work between the modules (files with POD in F<lib/>) | |
178 | and the core documentation (files in F<pod/>) | |
179 | ||
180 | =item 2 | |
181 | ||
78b489b0 NC |
182 | Improving the code that split C<perlfunc> into chunks, preferably with |
183 | general case code added to L<Pod::Functions> that could be used elsewhere. | |
184 | ||
617eabfa NC |
185 | Challenges here are correctly identifying the groups of functions that go |
186 | together, and making the right named external cross-links point to the right | |
78b489b0 NC |
187 | page. Currently this works reasonably well in the general case, and correctly |
188 | parses two or more C<=items> giving the different parameter lists for the | |
189 | same function, such used by C<substr>. However it fails completely where | |
190 | I<different> functions are listed as a sequence of C<=items> but share the | |
191 | same description. All the functions from C<getpwnam> to C<endprotoent> have | |
192 | individual stub pages, with only the page for C<endservent> holding the | |
193 | description common to all. Likewise C<q>, C<qq> and C<qw> have stub pages, | |
194 | instead of sharing the body of C<qx>. | |
195 | ||
196 | Note also the current code isn't ideal with the two forms of C<select>, mushing | |
197 | them both into one F<select.html> with the two descriptions run together. | |
198 | Fixing this may well be a special case. | |
adebf063 NC |
199 | |
200 | =back | |
3a89a73c | 201 | |
0bdfc961 NC |
202 | =head2 compressed man pages |
203 | ||
204 | Be able to install them. This would probably need a configure test to see how | |
205 | the system does compressed man pages (same directory/different directory? | |
206 | same filename/different filename), as well as tweaking the F<installman> script | |
207 | to compress as necessary. | |
208 | ||
30222c0f NC |
209 | =head2 Add a code coverage target to the Makefile |
210 | ||
211 | Make it easy for anyone to run Devel::Cover on the core's tests. The steps | |
212 | to do this manually are roughly | |
213 | ||
214 | =over 4 | |
215 | ||
216 | =item * | |
217 | ||
218 | do a normal C<Configure>, but include Devel::Cover as a module to install | |
f11a3063 | 219 | (see L<INSTALL> for how to do this) |
30222c0f NC |
220 | |
221 | =item * | |
222 | ||
223 | make perl | |
224 | ||
225 | =item * | |
226 | ||
227 | cd t; HARNESS_PERL_SWITCHES=-MDevel::Cover ./perl -I../lib harness | |
228 | ||
229 | =item * | |
230 | ||
231 | Process the resulting Devel::Cover database | |
232 | ||
233 | =back | |
234 | ||
235 | This just give you the coverage of the F<.pm>s. To also get the C level | |
236 | coverage you need to | |
237 | ||
238 | =over 4 | |
239 | ||
240 | =item * | |
241 | ||
242 | Additionally tell C<Configure> to use the appropriate C compiler flags for | |
243 | C<gcov> | |
244 | ||
245 | =item * | |
246 | ||
247 | make perl.gcov | |
248 | ||
249 | (instead of C<make perl>) | |
250 | ||
251 | =item * | |
252 | ||
253 | After running the tests run C<gcov> to generate all the F<.gcov> files. | |
254 | (Including down in the subdirectories of F<ext/> | |
255 | ||
256 | =item * | |
257 | ||
258 | (From the top level perl directory) run C<gcov2perl> on all the C<.gcov> files | |
259 | to get their stats into the cover_db directory. | |
260 | ||
261 | =item * | |
262 | ||
263 | Then process the Devel::Cover database | |
264 | ||
265 | =back | |
266 | ||
267 | It would be good to add a single switch to C<Configure> to specify that you | |
268 | wanted to perform perl level coverage, and another to specify C level | |
269 | coverage, and have C<Configure> and the F<Makefile> do all the right things | |
270 | automatically. | |
271 | ||
02f21748 | 272 | =head2 Make Config.pm cope with differences between built and installed perl |
0bdfc961 NC |
273 | |
274 | Quite often vendors ship a perl binary compiled with their (pay-for) | |
275 | compilers. People install a free compiler, such as gcc. To work out how to | |
276 | build extensions, Perl interrogates C<%Config>, so in this situation | |
277 | C<%Config> describes compilers that aren't there, and extension building | |
278 | fails. This forces people into choosing between re-compiling perl themselves | |
279 | using the compiler they have, or only using modules that the vendor ships. | |
280 | ||
281 | It would be good to find a way teach C<Config.pm> about the installation setup, | |
282 | possibly involving probing at install time or later, so that the C<%Config> in | |
283 | a binary distribution better describes the installed machine, when the | |
284 | installed machine differs from the build machine in some significant way. | |
285 | ||
728f4ecd NC |
286 | =head2 linker specification files |
287 | ||
288 | Some platforms mandate that you provide a list of a shared library's external | |
289 | symbols to the linker, so the core already has the infrastructure in place to | |
4e1c9055 NC |
290 | do this for generating shared perl libraries. Florian Ragwitz has been working |
291 | to offer this for the GNU toolchain, to allow Unix users to test that the | |
728f4ecd | 292 | export list is correct, and to build a perl that does not pollute the global |
32d539f5 | 293 | namespace with private symbols, and will fail in the same way as msvc or mingw |
4e1c9055 | 294 | builds or when using PERL_DL_NONLAZY=1. See the branch smoke-me/rafl/ld_export |
728f4ecd | 295 | |
a229ae3b RGS |
296 | =head2 Cross-compile support |
297 | ||
4e1c9055 NC |
298 | We get requests for "how to cross compile Perl". The vast majority of these |
299 | seem to be for a couple of scenarios: | |
300 | ||
301 | =over 4 | |
302 | ||
303 | =item * | |
304 | ||
305 | Platforms that could build natively using F<./Configure> (I<e.g.> Linux or | |
306 | NetBSD on MIPS or ARM) but people want to use a beefier machine (and on the | |
307 | same OS) to build more easily. | |
308 | ||
309 | =item * | |
310 | ||
311 | Platforms that can't build natively, but no (significant) porting changes | |
312 | are needed to our current source code. Prime example of this is Android. | |
313 | ||
314 | =back | |
315 | ||
316 | There are several scripts and tools for cross-compiling perl for other | |
317 | platforms. However, these are somewhat inconsistent and scattered across the | |
318 | codebase, none are documented well, none are clearly flexible enough to | |
319 | be confident that they can support any TARGET/HOST plaform pair other than | |
320 | that which they were developed on, and it's not clear how bitrotted they are. | |
321 | ||
322 | For example, C<Configure> understands C<-Dusecrosscompile> option. This option | |
a229ae3b | 323 | arranges for building C<miniperl> for TARGET machine, so this C<miniperl> is |
4e1c9055 NC |
324 | assumed then to be copied to TARGET machine and used as a replacement of |
325 | full C<perl> executable. This code is almost 10 years old. Meanwhile, the | |
326 | F<Cross/> directory contains two different approaches for cross compiling to | |
327 | ARM Linux targets, relying on hand curated F<config.sh> files, but that code | |
328 | is getting on for 5 years old, and requires insider knowledge of perl's | |
329 | build system to draft a F<config.sh> for a new platform. | |
330 | ||
331 | Jess Robinson has sumbitted a grant to TPF to work on cleaning this up. | |
0bdfc961 | 332 | |
98fca0e8 NC |
333 | =head2 Split "linker" from "compiler" |
334 | ||
335 | Right now, Configure probes for two commands, and sets two variables: | |
336 | ||
337 | =over 4 | |
338 | ||
b91dd380 | 339 | =item * C<cc> (in F<cc.U>) |
98fca0e8 NC |
340 | |
341 | This variable holds the name of a command to execute a C compiler which | |
342 | can resolve multiple global references that happen to have the same | |
343 | name. Usual values are F<cc> and F<gcc>. | |
344 | Fervent ANSI compilers may be called F<c89>. AIX has F<xlc>. | |
345 | ||
b91dd380 | 346 | =item * C<ld> (in F<dlsrc.U>) |
98fca0e8 NC |
347 | |
348 | This variable indicates the program to be used to link | |
349 | libraries for dynamic loading. On some systems, it is F<ld>. | |
350 | On ELF systems, it should be C<$cc>. Mostly, we'll try to respect | |
351 | the hint file setting. | |
352 | ||
353 | =back | |
354 | ||
8d159ec1 NC |
355 | There is an implicit historical assumption from around Perl5.000alpha |
356 | something, that C<$cc> is also the correct command for linking object files | |
357 | together to make an executable. This may be true on Unix, but it's not true | |
358 | on other platforms, and there are a maze of work arounds in other places (such | |
359 | as F<Makefile.SH>) to cope with this. | |
98fca0e8 NC |
360 | |
361 | Ideally, we should create a new variable to hold the name of the executable | |
362 | linker program, probe for it in F<Configure>, and centralise all the special | |
363 | case logic there or in hints files. | |
364 | ||
365 | A small bikeshed issue remains - what to call it, given that C<$ld> is already | |
8d159ec1 NC |
366 | taken (arguably for the wrong thing now, but on SunOS 4.1 it is the command |
367 | for creating dynamically-loadable modules) and C<$link> could be confused with | |
368 | the Unix command line executable of the same name, which does something | |
369 | completely different. Andy Dougherty makes the counter argument "In parrot, I | |
370 | tried to call the command used to link object files and libraries into an | |
371 | executable F<link>, since that's what my vaguely-remembered DOS and VMS | |
372 | experience suggested. I don't think any real confusion has ensued, so it's | |
373 | probably a reasonable name for perl5 to use." | |
98fca0e8 NC |
374 | |
375 | "Alas, I've always worried that introducing it would make things worse, | |
376 | since now the module building utilities would have to look for | |
377 | C<$Config{link}> and institute a fall-back plan if it weren't found." | |
8d159ec1 NC |
378 | Although I can see that as confusing, given that C<$Config{d_link}> is true |
379 | when (hard) links are available. | |
98fca0e8 | 380 | |
75585ce3 SP |
381 | =head2 Configure Windows using PowerShell |
382 | ||
383 | Currently, Windows uses hard-coded config files based to build the | |
384 | config.h for compiling Perl. Makefiles are also hard-coded and need to be | |
385 | hand edited prior to building Perl. While this makes it easy to create a perl.exe | |
386 | that works across multiple Windows versions, being able to accurately | |
387 | configure a perl.exe for a specific Windows versions and VS C++ would be | |
388 | a nice enhancement. With PowerShell available on Windows XP and up, this | |
389 | may now be possible. Step 1 might be to investigate whether this is possible | |
390 | and use this to clean up our current makefile situation. Step 2 would be to | |
391 | see if there would be a way to use our existing metaconfig units to configure a | |
392 | Windows Perl or whether we go in a separate direction and make it so. Of | |
393 | course, we all know what step 3 is. | |
394 | ||
0bdfc961 NC |
395 | =head1 Tasks that need a little C knowledge |
396 | ||
397 | These tasks would need a little C knowledge, but don't need any specific | |
398 | background or experience with XS, or how the Perl interpreter works | |
399 | ||
3d826b29 NC |
400 | =head2 Weed out needless PERL_UNUSED_ARG |
401 | ||
402 | The C code uses the macro C<PERL_UNUSED_ARG> to stop compilers warning about | |
403 | unused arguments. Often the arguments can't be removed, as there is an | |
404 | external constraint that determines the prototype of the function, so this | |
405 | approach is valid. However, there are some cases where C<PERL_UNUSED_ARG> | |
406 | could be removed. Specifically | |
407 | ||
408 | =over 4 | |
409 | ||
410 | =item * | |
411 | ||
412 | The prototypes of (nearly all) static functions can be changed | |
413 | ||
414 | =item * | |
415 | ||
416 | Unused arguments generated by short cut macros are wasteful - the short cut | |
417 | macro used can be changed. | |
418 | ||
419 | =back | |
420 | ||
bcbaa2d5 RGS |
421 | =head2 -Duse32bit* |
422 | ||
423 | Natively 64-bit systems need neither -Duse64bitint nor -Duse64bitall. | |
424 | On these systems, it might be the default compilation mode, and there | |
425 | is currently no guarantee that passing no use64bitall option to the | |
426 | Configure process will build a 32bit perl. Implementing -Duse32bit* | |
e12cb30b | 427 | options would be nice for perl 5.18.0. |
bcbaa2d5 | 428 | |
fee0a0f7 | 429 | =head2 Profile Perl - am I hot or not? |
62403a3c | 430 | |
fee0a0f7 NC |
431 | The Perl source code is stable enough that it makes sense to profile it, |
432 | identify and optimise the hotspots. It would be good to measure the | |
433 | performance of the Perl interpreter using free tools such as cachegrind, | |
434 | gprof, and dtrace, and work to reduce the bottlenecks they reveal. | |
435 | ||
436 | As part of this, the idea of F<pp_hot.c> is that it contains the I<hot> ops, | |
437 | the ops that are most commonly used. The idea is that by grouping them, their | |
438 | object code will be adjacent in the executable, so they have a greater chance | |
439 | of already being in the CPU cache (or swapped in) due to being near another op | |
440 | already in use. | |
62403a3c NC |
441 | |
442 | Except that it's not clear if these really are the most commonly used ops. So | |
fee0a0f7 NC |
443 | as part of exercising your skills with coverage and profiling tools you might |
444 | want to determine what ops I<really> are the most commonly used. And in turn | |
445 | suggest evictions and promotions to achieve a better F<pp_hot.c>. | |
62403a3c | 446 | |
91d0cbf6 NC |
447 | One piece of Perl code that might make a good testbed is F<installman>. |
448 | ||
a229ae3b | 449 | =head2 Improve win32/wince.c |
0bdfc961 | 450 | |
a229ae3b | 451 | Currently, numerous functions look virtually, if not completely, |
c23989d1 | 452 | identical in both F<win32/wince.c> and F<win32/win32.c> files, which can't |
6d71adcd NC |
453 | be good. |
454 | ||
c5b31784 SH |
455 | =head2 Use secure CRT functions when building with VC8 on Win32 |
456 | ||
457 | Visual C++ 2005 (VC++ 8.x) deprecated a number of CRT functions on the basis | |
458 | that they were "unsafe" and introduced differently named secure versions of | |
459 | them as replacements, e.g. instead of writing | |
460 | ||
461 | FILE* f = fopen(__FILE__, "r"); | |
462 | ||
463 | one should now write | |
464 | ||
465 | FILE* f; | |
466 | errno_t err = fopen_s(&f, __FILE__, "r"); | |
467 | ||
468 | Currently, the warnings about these deprecations have been disabled by adding | |
469 | -D_CRT_SECURE_NO_DEPRECATE to the CFLAGS. It would be nice to remove that | |
470 | warning suppressant and actually make use of the new secure CRT functions. | |
471 | ||
472 | There is also a similar issue with POSIX CRT function names like fileno having | |
473 | been deprecated in favour of ISO C++ conformant names like _fileno. These | |
26a6faa8 | 474 | warnings are also currently suppressed by adding -D_CRT_NONSTDC_NO_DEPRECATE. It |
c5b31784 SH |
475 | might be nice to do as Microsoft suggest here too, although, unlike the secure |
476 | functions issue, there is presumably little or no benefit in this case. | |
477 | ||
038ae9a4 SH |
478 | =head2 Fix POSIX::access() and chdir() on Win32 |
479 | ||
480 | These functions currently take no account of DACLs and therefore do not behave | |
481 | correctly in situations where access is restricted by DACLs (as opposed to the | |
482 | read-only attribute). | |
483 | ||
484 | Furthermore, POSIX::access() behaves differently for directories having the | |
485 | read-only attribute set depending on what CRT library is being used. For | |
486 | example, the _access() function in the VC6 and VC7 CRTs (wrongly) claim that | |
487 | such directories are not writable, whereas in fact all directories are writable | |
488 | unless access is denied by DACLs. (In the case of directories, the read-only | |
489 | attribute actually only means that the directory cannot be deleted.) This CRT | |
490 | bug is fixed in the VC8 and VC9 CRTs (but, of course, the directory may still | |
491 | not actually be writable if access is indeed denied by DACLs). | |
492 | ||
493 | For the chdir() issue, see ActiveState bug #74552: | |
b4af8972 | 494 | L<http://bugs.activestate.com/show_bug.cgi?id=74552> |
038ae9a4 SH |
495 | |
496 | Therefore, DACLs should be checked both for consistency across CRTs and for | |
497 | the correct answer. | |
498 | ||
499 | (Note that perl's -w operator should not be modified to check DACLs. It has | |
500 | been written so that it reflects the state of the read-only attribute, even | |
501 | for directories (whatever CRT is being used), for symmetry with chmod().) | |
502 | ||
16815324 NC |
503 | =head2 strcat(), strcpy(), strncat(), strncpy(), sprintf(), vsprintf() |
504 | ||
505 | Maybe create a utility that checks after each libperl.a creation that | |
506 | none of the above (nor sprintf(), vsprintf(), or *SHUDDER* gets()) | |
507 | ever creep back to libperl.a. | |
508 | ||
509 | nm libperl.a | ./miniperl -alne '$o = $F[0] if /:$/; print "$o $F[1]" if $F[0] eq "U" && $F[1] =~ /^(?:strn?c(?:at|py)|v?sprintf|gets)$/' | |
510 | ||
511 | Note, of course, that this will only tell whether B<your> platform | |
512 | is using those naughty interfaces. | |
513 | ||
2a930eea | 514 | =head2 -D_FORTIFY_SOURCE=2 |
de96509d | 515 | |
2a930eea | 516 | Recent glibcs support C<-D_FORTIFY_SOURCE=2> which gives |
de96509d | 517 | protection against various kinds of buffer overflow problems. |
2a930eea | 518 | It should probably be used for compiling Perl whenever available, |
de96509d | 519 | Configure and/or hints files should be adjusted to probe for the |
2a930eea | 520 | availability of these feature and enable it as appropriate. |
16815324 | 521 | |
8964cfe0 NC |
522 | =head2 Arenas for GPs? For MAGIC? |
523 | ||
524 | C<struct gp> and C<struct magic> are both currently allocated by C<malloc>. | |
525 | It might be a speed or memory saving to change to using arenas. Or it might | |
526 | not. It would need some suitable benchmarking first. In particular, C<GP>s | |
527 | can probably be changed with minimal compatibility impact (probably nothing | |
528 | outside of the core, or even outside of F<gv.c> allocates them), but they | |
529 | probably aren't allocated/deallocated often enough for a speed saving. Whereas | |
530 | C<MAGIC> is allocated/deallocated more often, but in turn, is also something | |
531 | more externally visible, so changing the rules here may bite external code. | |
532 | ||
3880c8ec NC |
533 | =head2 Shared arenas |
534 | ||
535 | Several SV body structs are now the same size, notably PVMG and PVGV, PVAV and | |
536 | PVHV, and PVCV and PVFM. It should be possible to allocate and return same | |
537 | sized bodies from the same actual arena, rather than maintaining one arena for | |
538 | each. This could save 4-6K per thread, of memory no longer tied up in the | |
539 | not-yet-allocated part of an arena. | |
540 | ||
8964cfe0 | 541 | |
6d71adcd NC |
542 | =head1 Tasks that need a knowledge of XS |
543 | ||
544 | These tasks would need C knowledge, and roughly the level of knowledge of | |
545 | the perl API that comes from writing modules that use XS to interface to | |
546 | C. | |
547 | ||
e851c105 DG |
548 | =head2 Write an XS cookbook |
549 | ||
550 | Create pod/perlxscookbook.pod with short, task-focused 'recipes' in XS that | |
551 | demonstrate common tasks and good practices. (Some of these might be | |
552 | extracted from perlguts.) The target audience should be XS novices, who need | |
553 | more examples than perlguts but something less overwhelming than perlapi. | |
554 | Recipes should provide "one pretty good way to do it" instead of TIMTOWTDI. | |
555 | ||
5b7d14ff DG |
556 | Rather than focusing on interfacing Perl to C libraries, such a cookbook |
557 | should probably focus on how to optimize Perl routines by re-writing them | |
558 | in XS. This will likely be more motivating to those who mostly work in | |
559 | Perl but are looking to take the next step into XS. | |
560 | ||
561 | Deconstructing and explaining some simpler XS modules could be one way to | |
562 | bootstrap a cookbook. (List::Util? Class::XSAccessor? Tree::Ternary_XS?) | |
563 | Another option could be deconstructing the implementation of some simpler | |
564 | functions in op.c. | |
565 | ||
0b162fb0 | 566 | =head2 Document how XSUBs can use C<cv_set_call_checker> to inline themselves as OPs |
05fb4e20 NC |
567 | |
568 | For a simple XSUB, often the subroutine dispatch takes more time than the | |
0b162fb0 NC |
569 | XSUB itself. v5.14.0 now allows XSUBs to register a function which will be |
570 | called when the parser is finished building an C<entersub> op which calls | |
571 | them. | |
572 | ||
573 | Registration is done with C<Perl_cv_set_call_checker>, is documented at the | |
574 | API level in L<perlapi>, and L<perl5140delta/Custom per-subroutine check hooks> | |
575 | notes that it can be used to inline a subroutine, by replacing it with a | |
576 | custom op. However there is no further detail of the code needed to do this. | |
577 | It would be useful to add one or more annotated examples of how to create | |
578 | XSUBs that inline. | |
579 | ||
580 | This should provide a measurable speed up to simple XSUBs inside | |
05fb4e20 NC |
581 | tight loops. Initially one would have to write the OP alternative |
582 | implementation by hand, but it's likely that this should be reasonably | |
583 | straightforward for the type of XSUB that would benefit the most. Longer | |
584 | term, once the run-time implementation is proven, it should be possible to | |
585 | progressively update ExtUtils::ParseXS to generate OP implementations for | |
586 | some XSUBs. | |
587 | ||
318bf708 NC |
588 | =head2 Remove the use of SVs as temporaries in dump.c |
589 | ||
590 | F<dump.c> contains debugging routines to dump out the contains of perl data | |
591 | structures, such as C<SV>s, C<AV>s and C<HV>s. Currently, the dumping code | |
592 | B<uses> C<SV>s for its temporary buffers, which was a logical initial | |
593 | implementation choice, as they provide ready made memory handling. | |
594 | ||
595 | However, they also lead to a lot of confusion when it happens that what you're | |
596 | trying to debug is seen by the code in F<dump.c>, correctly or incorrectly, as | |
597 | a temporary scalar it can use for a temporary buffer. It's also not possible | |
598 | to dump scalars before the interpreter is properly set up, such as during | |
599 | ithreads cloning. It would be good to progressively replace the use of scalars | |
600 | as string accumulation buffers with something much simpler, directly allocated | |
601 | by C<malloc>. The F<dump.c> code is (or should be) only producing 7 bit | |
602 | US-ASCII, so output character sets are not an issue. | |
603 | ||
604 | Producing and proving an internal simple buffer allocation would make it easier | |
605 | to re-write the internals of the PerlIO subsystem to avoid using C<SV>s for | |
606 | B<its> buffers, use of which can cause problems similar to those of F<dump.c>, | |
607 | at similar times. | |
608 | ||
5d96f598 NC |
609 | =head2 safely supporting POSIX SA_SIGINFO |
610 | ||
611 | Some years ago Jarkko supplied patches to provide support for the POSIX | |
612 | SA_SIGINFO feature in Perl, passing the extra data to the Perl signal handler. | |
613 | ||
614 | Unfortunately, it only works with "unsafe" signals, because under safe | |
615 | signals, by the time Perl gets to run the signal handler, the extra | |
616 | information has been lost. Moreover, it's not easy to store it somewhere, | |
617 | as you can't call mutexs, or do anything else fancy, from inside a signal | |
618 | handler. | |
619 | ||
620 | So it strikes me that we could provide safe SA_SIGINFO support | |
621 | ||
622 | =over 4 | |
623 | ||
624 | =item 1 | |
625 | ||
626 | Provide global variables for two file descriptors | |
627 | ||
628 | =item 2 | |
629 | ||
630 | When the first request is made via C<sigaction> for C<SA_SIGINFO>, create a | |
631 | pipe, store the reader in one, the writer in the other | |
632 | ||
633 | =item 3 | |
634 | ||
635 | In the "safe" signal handler (C<Perl_csighandler()>/C<S_raise_signal()>), if | |
636 | the C<siginfo_t> pointer non-C<NULL>, and the writer file handle is open, | |
637 | ||
638 | =over 8 | |
639 | ||
640 | =item 1 | |
641 | ||
642 | serialise signal number, C<struct siginfo_t> (or at least the parts we care | |
643 | about) into a small auto char buff | |
644 | ||
645 | =item 2 | |
646 | ||
647 | C<write()> that (non-blocking) to the writer fd | |
648 | ||
649 | =over 12 | |
650 | ||
651 | =item 1 | |
652 | ||
653 | if it writes 100%, flag the signal in a counter of "signals on the pipe" akin | |
654 | to the current per-signal-number counts | |
655 | ||
656 | =item 2 | |
657 | ||
658 | if it writes 0%, assume the pipe is full. Flag the data as lost? | |
659 | ||
660 | =item 3 | |
661 | ||
662 | if it writes partially, croak a panic, as your OS is broken. | |
663 | ||
664 | =back | |
665 | ||
666 | =back | |
667 | ||
668 | =item 4 | |
669 | ||
670 | in the regular C<PERL_ASYNC_CHECK()> processing, if there are "signals on | |
671 | the pipe", read the data out, deserialise, build the Perl structures on | |
672 | the stack (code in C<Perl_sighandler()>, the "unsafe" handler), and call as | |
673 | usual. | |
674 | ||
675 | =back | |
676 | ||
677 | I think that this gets us decent C<SA_SIGINFO> support, without the current risk | |
678 | of running Perl code inside the signal handler context. (With all the dangers | |
679 | of things like C<malloc> corruption that that currently offers us) | |
680 | ||
681 | For more information see the thread starting with this message: | |
b4af8972 | 682 | L<http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/2008-03/msg00305.html> |
5d96f598 | 683 | |
6d71adcd NC |
684 | =head2 autovivification |
685 | ||
686 | Make all autovivification consistent w.r.t LVALUE/RVALUE and strict/no strict; | |
687 | ||
688 | This task is incremental - even a little bit of work on it will help. | |
689 | ||
690 | =head2 Unicode in Filenames | |
691 | ||
692 | chdir, chmod, chown, chroot, exec, glob, link, lstat, mkdir, open, | |
693 | opendir, qx, readdir, readlink, rename, rmdir, stat, symlink, sysopen, | |
694 | system, truncate, unlink, utime, -X. All these could potentially accept | |
695 | Unicode filenames either as input or output (and in the case of system | |
696 | and qx Unicode in general, as input or output to/from the shell). | |
697 | Whether a filesystem - an operating system pair understands Unicode in | |
698 | filenames varies. | |
699 | ||
700 | Known combinations that have some level of understanding include | |
701 | Microsoft NTFS, Apple HFS+ (In Mac OS 9 and X) and Apple UFS (in Mac | |
702 | OS X), NFS v4 is rumored to be Unicode, and of course Plan 9. How to | |
703 | create Unicode filenames, what forms of Unicode are accepted and used | |
704 | (UCS-2, UTF-16, UTF-8), what (if any) is the normalization form used, | |
705 | and so on, varies. Finding the right level of interfacing to Perl | |
706 | requires some thought. Remember that an OS does not implicate a | |
707 | filesystem. | |
708 | ||
709 | (The Windows -C command flag "wide API support" has been at least | |
710 | temporarily retired in 5.8.1, and the -C has been repurposed, see | |
711 | L<perlrun>.) | |
712 | ||
87a942b1 JH |
713 | Most probably the right way to do this would be this: |
714 | L</"Virtualize operating system access">. | |
715 | ||
6d71adcd NC |
716 | =head2 Unicode in %ENV |
717 | ||
718 | Currently the %ENV entries are always byte strings. | |
87a942b1 | 719 | See L</"Virtualize operating system access">. |
6d71adcd | 720 | |
799c141b SH |
721 | (See RT ticket #113536 for information on Win32's handling of %ENV, |
722 | which was fixed to work with native ANSI codepage characters in the | |
723 | environment, but still doesn't work with other characters outside of | |
724 | that codepage present in the environment.) | |
725 | ||
1f2e7916 JD |
726 | =head2 Unicode and glob() |
727 | ||
728 | Currently glob patterns and filenames returned from File::Glob::glob() | |
87a942b1 | 729 | are always byte strings. See L</"Virtualize operating system access">. |
1f2e7916 | 730 | |
6d71adcd NC |
731 | =head2 use less 'memory' |
732 | ||
733 | Investigate trade offs to switch out perl's choices on memory usage. | |
734 | Particularly perl should be able to give memory back. | |
735 | ||
736 | This task is incremental - even a little bit of work on it will help. | |
737 | ||
738 | =head2 Re-implement C<:unique> in a way that is actually thread-safe | |
739 | ||
740 | The old implementation made bad assumptions on several levels. A good 90% | |
741 | solution might be just to make C<:unique> work to share the string buffer | |
742 | of SvPVs. That way large constant strings can be shared between ithreads, | |
743 | such as the configuration information in F<Config>. | |
744 | ||
745 | =head2 Make tainting consistent | |
746 | ||
747 | Tainting would be easier to use if it didn't take documented shortcuts and | |
748 | allow taint to "leak" everywhere within an expression. | |
749 | ||
750 | =head2 readpipe(LIST) | |
751 | ||
752 | system() accepts a LIST syntax (and a PROGRAM LIST syntax) to avoid | |
753 | running a shell. readpipe() (the function behind qx//) could be similarly | |
754 | extended. | |
755 | ||
6d71adcd NC |
756 | =head2 Audit the code for destruction ordering assumptions |
757 | ||
758 | Change 25773 notes | |
759 | ||
760 | /* Need to check SvMAGICAL, as during global destruction it may be that | |
761 | AvARYLEN(av) has been freed before av, and hence the SvANY() pointer | |
762 | is now part of the linked list of SV heads, rather than pointing to | |
763 | the original body. */ | |
764 | /* FIXME - audit the code for other bugs like this one. */ | |
765 | ||
766 | adding the C<SvMAGICAL> check to | |
767 | ||
768 | if (AvARYLEN(av) && SvMAGICAL(AvARYLEN(av))) { | |
769 | MAGIC *mg = mg_find (AvARYLEN(av), PERL_MAGIC_arylen); | |
770 | ||
771 | Go through the core and look for similar assumptions that SVs have particular | |
772 | types, as all bets are off during global destruction. | |
773 | ||
749904bf JH |
774 | =head2 Extend PerlIO and PerlIO::Scalar |
775 | ||
776 | PerlIO::Scalar doesn't know how to truncate(). Implementing this | |
777 | would require extending the PerlIO vtable. | |
778 | ||
779 | Similarly the PerlIO vtable doesn't know about formats (write()), or | |
780 | about stat(), or chmod()/chown(), utime(), or flock(). | |
781 | ||
782 | (For PerlIO::Scalar it's hard to see what e.g. mode bits or ownership | |
783 | would mean.) | |
784 | ||
785 | PerlIO doesn't do directories or symlinks, either: mkdir(), rmdir(), | |
786 | opendir(), closedir(), seekdir(), rewinddir(), glob(); symlink(), | |
787 | readlink(). | |
788 | ||
94da6c29 JH |
789 | See also L</"Virtualize operating system access">. |
790 | ||
d6c1e11f JH |
791 | =head2 Organize error messages |
792 | ||
793 | Perl's diagnostics (error messages, see L<perldiag>) could use | |
a8d0aeb9 | 794 | reorganizing and formalizing so that each error message has its |
d6c1e11f JH |
795 | stable-for-all-eternity unique id, categorized by severity, type, and |
796 | subsystem. (The error messages would be listed in a datafile outside | |
c4bd451b CB |
797 | of the Perl source code, and the source code would only refer to the |
798 | messages by the id.) This clean-up and regularizing should apply | |
d6c1e11f JH |
799 | for all croak() messages. |
800 | ||
801 | This would enable all sorts of things: easier translation/localization | |
802 | of the messages (though please do keep in mind the caveats of | |
803 | L<Locale::Maketext> about too straightforward approaches to | |
804 | translation), filtering by severity, and instead of grepping for a | |
805 | particular error message one could look for a stable error id. (Of | |
806 | course, changing the error messages by default would break all the | |
807 | existing software depending on some particular error message...) | |
808 | ||
809 | This kind of functionality is known as I<message catalogs>. Look for | |
810 | inspiration for example in the catgets() system, possibly even use it | |
811 | if available-- but B<only> if available, all platforms will B<not> | |
de96509d | 812 | have catgets(). |
d6c1e11f JH |
813 | |
814 | For the really pure at heart, consider extending this item to cover | |
815 | also the warning messages (see L<perllexwarn>, C<warnings.pl>). | |
3236f110 | 816 | |
0bdfc961 | 817 | =head1 Tasks that need a knowledge of the interpreter |
3298bd4d | 818 | |
0bdfc961 NC |
819 | These tasks would need C knowledge, and knowledge of how the interpreter works, |
820 | or a willingness to learn. | |
3298bd4d | 821 | |
10517af5 JD |
822 | =head2 forbid labels with keyword names |
823 | ||
824 | Currently C<goto keyword> "computes" the label value: | |
825 | ||
826 | $ perl -e 'goto print' | |
827 | Can't find label 1 at -e line 1. | |
828 | ||
343c8006 JD |
829 | It is controversial if the right way to avoid the confusion is to forbid |
830 | labels with keyword names, or if it would be better to always treat | |
831 | bareword expressions after a "goto" as a label and never as a keyword. | |
10517af5 | 832 | |
de6375e3 RGS |
833 | =head2 truncate() prototype |
834 | ||
835 | The prototype of truncate() is currently C<$$>. It should probably | |
836 | be C<*$> instead. (This is changed in F<opcode.pl>) | |
837 | ||
565590b5 NC |
838 | =head2 error reporting of [$a ; $b] |
839 | ||
840 | Using C<;> inside brackets is a syntax error, and we don't propose to change | |
841 | that by giving it any meaning. However, it's not reported very helpfully: | |
842 | ||
843 | $ perl -e '$a = [$b; $c];' | |
844 | syntax error at -e line 1, near "$b;" | |
845 | syntax error at -e line 1, near "$c]" | |
846 | Execution of -e aborted due to compilation errors. | |
847 | ||
848 | It should be possible to hook into the tokeniser or the lexer, so that when a | |
849 | C<;> is parsed where it is not legal as a statement terminator (ie inside | |
850 | C<{}> used as a hashref, C<[]> or C<()>) it issues an error something like | |
851 | I<';' isn't legal inside an expression - if you need multiple statements use a | |
852 | do {...} block>. See the thread starting at | |
b4af8972 | 853 | L<http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/2008-09/msg00573.html> |
565590b5 | 854 | |
e053a921 RS |
855 | =head2 strict as warnings |
856 | ||
857 | See L<http://markmail.org/message/vbrupaslr3bybmvk>, where Josua ben Jore | |
858 | writes: I've been of the opinion that everything strict.pm does ought to be | |
859 | able to considered just warnings that have been promoted to 'FATAL'. | |
860 | ||
718140ec NC |
861 | =head2 lexicals used only once |
862 | ||
863 | This warns: | |
864 | ||
865 | $ perl -we '$pie = 42' | |
866 | Name "main::pie" used only once: possible typo at -e line 1. | |
867 | ||
868 | This does not: | |
869 | ||
870 | $ perl -we 'my $pie = 42' | |
871 | ||
872 | Logically all lexicals used only once should warn, if the user asks for | |
d6f4ea2e SP |
873 | warnings. An unworked RT ticket (#5087) has been open for almost seven |
874 | years for this discrepancy. | |
718140ec | 875 | |
a3d15f9a RGS |
876 | =head2 UTF-8 revamp |
877 | ||
85c006b6 KW |
878 | The handling of Unicode is unclean in many places. In the regex engine |
879 | there are especially many problems. The swash data structure could be | |
880 | replaced my something better. Inversion lists and maps are likely | |
881 | candidates. The whole Unicode database could be placed in-core for a | |
882 | huge speed-up. Only minimal work was done on the optimizer when utf8 | |
883 | was added, with the result that the synthetic start class often will | |
884 | fail to narrow down the possible choices when given non-Latin1 input. | |
4e1c9055 | 885 | Karl Williamson has been working on this - talk to him. |
a3d15f9a | 886 | |
636e63cb NC |
887 | =head2 state variable initialization in list context |
888 | ||
889 | Currently this is illegal: | |
890 | ||
891 | state ($a, $b) = foo(); | |
892 | ||
a2874905 | 893 | In Perl 6, C<state ($a) = foo();> and C<(state $a) = foo();> have different |
a8d0aeb9 | 894 | semantics, which is tricky to implement in Perl 5 as currently they produce |
a2874905 | 895 | the same opcode trees. The Perl 6 design is firm, so it would be good to |
a8d0aeb9 | 896 | implement the necessary code in Perl 5. There are comments in |
a2874905 NC |
897 | C<Perl_newASSIGNOP()> that show the code paths taken by various assignment |
898 | constructions involving state variables. | |
636e63cb | 899 | |
a393eb28 RGS |
900 | =head2 A does() built-in |
901 | ||
902 | Like ref(), only useful. It would call the C<DOES> method on objects; it | |
903 | would also tell whether something can be dereferenced as an | |
904 | array/hash/etc., or used as a regexp, etc. | |
905 | L<http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/2007-03/msg00481.html> | |
906 | ||
907 | =head2 Tied filehandles and write() don't mix | |
908 | ||
909 | There is no method on tied filehandles to allow them to be called back by | |
910 | formats. | |
4fedb12c | 911 | |
53967bb9 RGS |
912 | =head2 Propagate compilation hints to the debugger |
913 | ||
914 | Currently a debugger started with -dE on the command-line doesn't see the | |
915 | features enabled by -E. More generally hints (C<$^H> and C<%^H>) aren't | |
916 | propagated to the debugger. Probably it would be a good thing to propagate | |
917 | hints from the innermost non-C<DB::> scope: this would make code eval'ed | |
918 | in the debugger see the features (and strictures, etc.) currently in | |
919 | scope. | |
920 | ||
d10fc472 | 921 | =head2 Attach/detach debugger from running program |
1626a787 | 922 | |
cd793d32 NC |
923 | The old perltodo notes "With C<gdb>, you can attach the debugger to a running |
924 | program if you pass the process ID. It would be good to do this with the Perl | |
0bdfc961 NC |
925 | debugger on a running Perl program, although I'm not sure how it would be |
926 | done." ssh and screen do this with named pipes in /tmp. Maybe we can too. | |
1626a787 | 927 | |
0bdfc961 NC |
928 | =head2 LVALUE functions for lists |
929 | ||
930 | The old perltodo notes that lvalue functions don't work for list or hash | |
931 | slices. This would be good to fix. | |
932 | ||
0bdfc961 NC |
933 | =head2 regexp optimiser optional |
934 | ||
935 | The regexp optimiser is not optional. It should configurable to be, to allow | |
936 | its performance to be measured, and its bugs to be easily demonstrated. | |
937 | ||
ef36c6a7 RGS |
938 | =head2 C</w> regex modifier |
939 | ||
940 | That flag would enable to match whole words, and also to interpolate | |
941 | arrays as alternations. With it, C</P/w> would be roughly equivalent to: | |
942 | ||
943 | do { local $"='|'; /\b(?:P)\b/ } | |
944 | ||
b4af8972 RB |
945 | See |
946 | L<http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/2007-01/msg00400.html> | |
ef36c6a7 RGS |
947 | for the discussion. |
948 | ||
0bdfc961 NC |
949 | =head2 optional optimizer |
950 | ||
951 | Make the peephole optimizer optional. Currently it performs two tasks as | |
952 | it walks the optree - genuine peephole optimisations, and necessary fixups of | |
953 | ops. It would be good to find an efficient way to switch out the | |
954 | optimisations whilst keeping the fixups. | |
955 | ||
956 | =head2 You WANT *how* many | |
957 | ||
958 | Currently contexts are void, scalar and list. split has a special mechanism in | |
959 | place to pass in the number of return values wanted. It would be useful to | |
960 | have a general mechanism for this, backwards compatible and little speed hit. | |
961 | This would allow proposals such as short circuiting sort to be implemented | |
962 | as a module on CPAN. | |
963 | ||
964 | =head2 lexical aliases | |
965 | ||
e12cb30b | 966 | Allow lexical aliases (maybe via the syntax C<my \$alias = \$foo>). |
0bdfc961 | 967 | |
de535794 | 968 | =head2 Self-ties |
2810d901 | 969 | |
de535794 | 970 | Self-ties are currently illegal because they caused too many segfaults. Maybe |
a8d0aeb9 | 971 | the causes of these could be tracked down and self-ties on all types |
de535794 | 972 | reinstated. |
0bdfc961 NC |
973 | |
974 | =head2 Optimize away @_ | |
975 | ||
976 | The old perltodo notes "Look at the "reification" code in C<av.c>". | |
977 | ||
87a942b1 JH |
978 | =head2 Virtualize operating system access |
979 | ||
980 | Implement a set of "vtables" that virtualizes operating system access | |
981 | (open(), mkdir(), unlink(), readdir(), getenv(), etc.) At the very | |
982 | least these interfaces should take SVs as "name" arguments instead of | |
983 | bare char pointers; probably the most flexible and extensible way | |
e1a3d5d1 JH |
984 | would be for the Perl-facing interfaces to accept HVs. The system |
985 | needs to be per-operating-system and per-file-system | |
986 | hookable/filterable, preferably both from XS and Perl level | |
87a942b1 JH |
987 | (L<perlport/"Files and Filesystems"> is good reading at this point, |
988 | in fact, all of L<perlport> is.) | |
989 | ||
e1a3d5d1 JH |
990 | This has actually already been implemented (but only for Win32), |
991 | take a look at F<iperlsys.h> and F<win32/perlhost.h>. While all Win32 | |
992 | variants go through a set of "vtables" for operating system access, | |
e1020413 | 993 | non-Win32 systems currently go straight for the POSIX/Unix-style |
e1a3d5d1 JH |
994 | system/library call. Similar system as for Win32 should be |
995 | implemented for all platforms. The existing Win32 implementation | |
996 | probably does not need to survive alongside this proposed new | |
997 | implementation, the approaches could be merged. | |
87a942b1 JH |
998 | |
999 | What would this give us? One often-asked-for feature this would | |
94da6c29 JH |
1000 | enable is using Unicode for filenames, and other "names" like %ENV, |
1001 | usernames, hostnames, and so forth. | |
1002 | (See L<perlunicode/"When Unicode Does Not Happen">.) | |
1003 | ||
1004 | But this kind of virtualization would also allow for things like | |
1005 | virtual filesystems, virtual networks, and "sandboxes" (though as long | |
1006 | as dynamic loading of random object code is allowed, not very safe | |
1007 | sandboxes since external code of course know not of Perl's vtables). | |
1008 | An example of a smaller "sandbox" is that this feature can be used to | |
1009 | implement per-thread working directories: Win32 already does this. | |
1010 | ||
1011 | See also L</"Extend PerlIO and PerlIO::Scalar">. | |
87a942b1 | 1012 | |
52960e22 JC |
1013 | =head2 repack the optree |
1014 | ||
1015 | Repacking the optree after execution order is determined could allow | |
057163d7 | 1016 | removal of NULL ops, and optimal ordering of OPs with respect to cache-line |
2723c0fb | 1017 | filling. I think that |
057163d7 NC |
1018 | the best way to do this is to make it an optional step just before the |
1019 | completed optree is attached to anything else, and to use the slab allocator | |
2723c0fb FC |
1020 | unchanged--but allocate a single slab the right size, avoiding partial |
1021 | slabs--, so that freeing ops is identical whether or not this step runs. | |
057163d7 NC |
1022 | Note that the slab allocator allocates ops downwards in memory, so one would |
1023 | have to actually "allocate" the ops in reverse-execution order to get them | |
1024 | contiguous in memory in execution order. | |
1025 | ||
b4af8972 RB |
1026 | See |
1027 | L<http://www.nntp.perl.org/group/perl.perl5.porters/2007/12/msg131975.html> | |
057163d7 NC |
1028 | |
1029 | Note that running this copy, and then freeing all the old location ops would | |
1030 | cause their slabs to be freed, which would eliminate possible memory wastage if | |
1031 | the previous suggestion is implemented, and we swap slabs more frequently. | |
52960e22 | 1032 | |
12e06b6f NC |
1033 | =head2 eliminate incorrect line numbers in warnings |
1034 | ||
1035 | This code | |
1036 | ||
1037 | use warnings; | |
1038 | my $undef; | |
1039 | ||
1040 | if ($undef == 3) { | |
1041 | } elsif ($undef == 0) { | |
1042 | } | |
1043 | ||
18a16cc5 | 1044 | used to produce this output: |
12e06b6f NC |
1045 | |
1046 | Use of uninitialized value in numeric eq (==) at wrong.pl line 4. | |
1047 | Use of uninitialized value in numeric eq (==) at wrong.pl line 4. | |
1048 | ||
18a16cc5 NC |
1049 | where the line of the second warning was misreported - it should be line 5. |
1050 | Rafael fixed this - the problem arose because there was no nextstate OP | |
1051 | between the execution of the C<if> and the C<elsif>, hence C<PL_curcop> still | |
1052 | reports that the currently executing line is line 4. The solution was to inject | |
1053 | a nextstate OPs for each C<elsif>, although it turned out that the nextstate | |
1054 | OP needed to be a nulled OP, rather than a live nextstate OP, else other line | |
1055 | numbers became misreported. (Jenga!) | |
12e06b6f NC |
1056 | |
1057 | The problem is more general than C<elsif> (although the C<elsif> case is the | |
1058 | most common and the most confusing). Ideally this code | |
1059 | ||
1060 | use warnings; | |
1061 | my $undef; | |
1062 | ||
1063 | my $a = $undef + 1; | |
1064 | my $b | |
1065 | = $undef | |
1066 | + 1; | |
1067 | ||
1068 | would produce this output | |
1069 | ||
1070 | Use of uninitialized value $undef in addition (+) at wrong.pl line 4. | |
1071 | Use of uninitialized value $undef in addition (+) at wrong.pl line 7. | |
1072 | ||
1073 | (rather than lines 4 and 5), but this would seem to require every OP to carry | |
1074 | (at least) line number information. | |
1075 | ||
1076 | What might work is to have an optional line number in memory just before the | |
1077 | BASEOP structure, with a flag bit in the op to say whether it's present. | |
1078 | Initially during compile every OP would carry its line number. Then add a late | |
1079 | pass to the optimiser (potentially combined with L</repack the optree>) which | |
1080 | looks at the two ops on every edge of the graph of the execution path. If | |
1081 | the line number changes, flags the destination OP with this information. | |
1082 | Once all paths are traced, replace every op with the flag with a | |
1083 | nextstate-light op (that just updates C<PL_curcop>), which in turn then passes | |
1084 | control on to the true op. All ops would then be replaced by variants that | |
1085 | do not store the line number. (Which, logically, why it would work best in | |
1086 | conjunction with L</repack the optree>, as that is already copying/reallocating | |
1087 | all the OPs) | |
1088 | ||
18a16cc5 NC |
1089 | (Although I should note that we're not certain that doing this for the general |
1090 | case is worth it) | |
1091 | ||
52960e22 JC |
1092 | =head2 optimize tail-calls |
1093 | ||
1094 | Tail-calls present an opportunity for broadly applicable optimization; | |
1095 | anywhere that C<< return foo(...) >> is called, the outer return can | |
1096 | be replaced by a goto, and foo will return directly to the outer | |
1097 | caller, saving (conservatively) 25% of perl's call&return cost, which | |
1098 | is relatively higher than in C. The scheme language is known to do | |
1099 | this heavily. B::Concise provides good insight into where this | |
1100 | optimization is possible, ie anywhere entersub,leavesub op-sequence | |
1101 | occurs. | |
1102 | ||
1103 | perl -MO=Concise,-exec,a,b,-main -e 'sub a{ 1 }; sub b {a()}; b(2)' | |
1104 | ||
1105 | Bottom line on this is probably a new pp_tailcall function which | |
1106 | combines the code in pp_entersub, pp_leavesub. This should probably | |
1107 | be done 1st in XS, and using B::Generate to patch the new OP into the | |
1108 | optrees. | |
1109 | ||
e12cb30b | 1110 | =head2 Add C<0odddd> |
0c397127 KW |
1111 | |
1112 | It has been proposed that octal constants be specifiable through the syntax | |
1113 | C<0oddddd>, parallel to the existing construct to specify hex constants | |
1114 | C<0xddddd> | |
1115 | ||
0bdfc961 NC |
1116 | =head1 Big projects |
1117 | ||
1118 | Tasks that will get your name mentioned in the description of the "Highlights | |
e12cb30b | 1119 | of 5.18.0" |
0bdfc961 NC |
1120 | |
1121 | =head2 make ithreads more robust | |
1122 | ||
45a81a90 | 1123 | Generally make ithreads more robust. |
0bdfc961 NC |
1124 | |
1125 | This task is incremental - even a little bit of work on it will help, and | |
1126 | will be greatly appreciated. | |
1127 | ||
07577ec1 FC |
1128 | One bit would be to determine how to clone directory handles on systems |
1129 | without a C<fchdir> function (in sv.c:Perl_dirp_dup). | |
6c047da7 | 1130 | |
59c7f7d5 RGS |
1131 | Fix Perl_sv_dup, et al so that threads can return objects. |
1132 | ||
6bda09f9 YO |
1133 | =head2 Add class set operations to regexp engine |
1134 | ||
1135 | Apparently these are quite useful. Anyway, Jeffery Friedl wants them. | |
1136 | ||
1137 | demerphq has this on his todo list, but right at the bottom. | |
44a7a252 JV |
1138 | |
1139 | ||
1140 | =head1 Tasks for microperl | |
1141 | ||
1142 | ||
1143 | [ Each and every one of these may be obsolete, but they were listed | |
1144 | in the old Todo.micro file] | |
1145 | ||
44a7a252 JV |
1146 | =head2 do away with fork/exec/wait? |
1147 | ||
1148 | (system, popen should be enough?) | |
1149 | ||
1150 | =head2 some of the uconfig.sh really needs to be probed (using cc) in buildtime: | |
1151 | ||
1152 | (uConfigure? :-) native datatype widths and endianness come to mind | |
1153 |