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1 | =head1 NAME |
2 | ||
3 | perltodo - Perl TO-DO List | |
4 | ||
5 | =head1 DESCRIPTION | |
e50bb9a1 | 6 | |
049aabcb NC |
7 | This is a list of wishes for Perl. The most up to date version of this file |
8 | is at http://perl5.git.perl.org/perl.git/blob_plain/HEAD:/pod/perltodo.pod | |
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 | |
18 | ideas, and any discussion about them. One set of archives may be found at: | |
e50bb9a1 | 19 | |
0bdfc961 | 20 | http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/ |
938c8732 | 21 | |
617eabfa NC |
22 | What can we offer you in return? Fame, fortune, and everlasting glory? Maybe |
23 | not, but if your patch is incorporated, then we'll add your name to the | |
24 | F<AUTHORS> file, which ships in the official distribution. How many other | |
25 | programming languages offer you 1 line of immortality? | |
938c8732 | 26 | |
0bdfc961 | 27 | =head1 Tasks that only need Perl knowledge |
e50bb9a1 | 28 | |
de2b17d8 NC |
29 | =head2 Migrate t/ from custom TAP generation |
30 | ||
31 | Many tests below F<t/> still generate TAP by "hand", rather than using library | |
32 | functions. As explained in L<perlhack/Writing a test>, tests in F<t/> are | |
33 | written in a particular way to test that more complex constructions actually | |
34 | work before using them routinely. Hence they don't use C<Test::More>, but | |
35 | instead there is an intentionally simpler library, F<t/test.pl>. However, | |
36 | quite a few tests in F<t/> have not been refactored to use it. Refactoring | |
37 | any of these tests, one at a time, is a useful thing TODO. | |
38 | ||
0d8e5a42 RGS |
39 | The subdirectories F<base>, F<cmd> and F<comp>, that contain the most |
40 | basic tests, should be excluded from this task. | |
41 | ||
08063926 NC |
42 | =head2 Test that regen.pl was run |
43 | ||
44 | There are various generated files shipped with the perl distribution, for | |
45 | things like header files generate from data. The generation scripts are | |
46 | written in perl, and all can be run by F<regen.pl>. However, because they're | |
47 | written in perl, we can't run them before we've built perl. We can't run them | |
48 | as part of the F<Makefile>, because changing files underneath F<make> confuses | |
49 | it completely, and we don't want to run them automatically anyway, as they | |
50 | change files shipped by the distribution, something we seek not do to. | |
51 | ||
52 | If someone changes the data, but forgets to re-run F<regen.pl> then the | |
53 | generated files are out of sync. It would be good to have a test in | |
54 | F<t/porting> that checks that the generated files are in sync, and fails | |
55 | otherwise, to alert someone before they make a poor commit. I suspect that this | |
56 | would require adapting the scripts run from F<regen.pl> to have dry-run | |
57 | options, and invoking them with these, or by refactoring them into a library | |
58 | that does the generation, which can be called by the scripts, and by the test. | |
59 | ||
0be987a2 NC |
60 | =head2 Automate perldelta generation |
61 | ||
62 | The perldelta file accompanying each release summaries the major changes. | |
63 | It's mostly manually generated currently, but some of that could be | |
64 | automated with a bit of perl, specifically the generation of | |
65 | ||
66 | =over | |
67 | ||
68 | =item Modules and Pragmata | |
69 | ||
70 | =item New Documentation | |
71 | ||
72 | =item New Tests | |
73 | ||
74 | =back | |
75 | ||
76 | See F<Porting/how_to_write_a_perldelta.pod> for details. | |
77 | ||
5a176cbc NC |
78 | =head2 Remove duplication of test setup. |
79 | ||
80 | Schwern notes, that there's duplication of code - lots and lots of tests have | |
81 | some variation on the big block of C<$Is_Foo> checks. We can safely put this | |
82 | into a file, change it to build an C<%Is> hash and require it. Maybe just put | |
83 | it into F<test.pl>. Throw in the handy tainting subroutines. | |
84 | ||
87a942b1 | 85 | =head2 POD -E<gt> HTML conversion in the core still sucks |
e50bb9a1 | 86 | |
938c8732 | 87 | Which is crazy given just how simple POD purports to be, and how simple HTML |
adebf063 NC |
88 | can be. It's not actually I<as> simple as it sounds, particularly with the |
89 | flexibility POD allows for C<=item>, but it would be good to improve the | |
90 | visual appeal of the HTML generated, and to avoid it having any validation | |
91 | errors. See also L</make HTML install work>, as the layout of installation tree | |
92 | is needed to improve the cross-linking. | |
938c8732 | 93 | |
dc0fb092 SP |
94 | The addition of C<Pod::Simple> and its related modules may make this task |
95 | easier to complete. | |
96 | ||
0befdfba NC |
97 | =head2 Make ExtUtils::ParseXS use strict; |
98 | ||
99 | F<lib/ExtUtils/ParseXS.pm> contains this line | |
100 | ||
101 | # use strict; # One of these days... | |
102 | ||
103 | Simply uncomment it, and fix all the resulting issues :-) | |
104 | ||
105 | The more practical approach, to break the task down into manageable chunks, is | |
106 | to work your way though the code from bottom to top, or if necessary adding | |
107 | extra C<{ ... }> blocks, and turning on strict within them. | |
108 | ||
0bdfc961 | 109 | =head2 Make Schwern poorer |
e50bb9a1 | 110 | |
613bd4f7 | 111 | We should have tests for everything. When all the core's modules are tested, |
0bdfc961 NC |
112 | Schwern has promised to donate to $500 to TPF. We may need volunteers to |
113 | hold him upside down and shake vigorously in order to actually extract the | |
114 | cash. | |
3958b146 | 115 | |
0bdfc961 | 116 | =head2 Improve the coverage of the core tests |
e50bb9a1 | 117 | |
e1020413 | 118 | Use Devel::Cover to ascertain the core modules' test coverage, then add |
02f21748 | 119 | tests that are currently missing. |
30222c0f | 120 | |
0bdfc961 | 121 | =head2 test B |
e50bb9a1 | 122 | |
0bdfc961 | 123 | A full test suite for the B module would be nice. |
e50bb9a1 | 124 | |
0bdfc961 | 125 | =head2 A decent benchmark |
e50bb9a1 | 126 | |
617eabfa | 127 | C<perlbench> seems impervious to any recent changes made to the perl core. It |
0bdfc961 NC |
128 | would be useful to have a reasonable general benchmarking suite that roughly |
129 | represented what current perl programs do, and measurably reported whether | |
130 | tweaks to the core improve, degrade or don't really affect performance, to | |
131 | guide people attempting to optimise the guts of perl. Gisle would welcome | |
132 | new tests for perlbench. | |
6168cf99 | 133 | |
0bdfc961 | 134 | =head2 fix tainting bugs |
6168cf99 | 135 | |
0bdfc961 NC |
136 | Fix the bugs revealed by running the test suite with the C<-t> switch (via |
137 | C<make test.taintwarn>). | |
e50bb9a1 | 138 | |
0bdfc961 | 139 | =head2 Dual life everything |
e50bb9a1 | 140 | |
0bdfc961 NC |
141 | As part of the "dists" plan, anything that doesn't belong in the smallest perl |
142 | distribution needs to be dual lifed. Anything else can be too. Figure out what | |
143 | changes would be needed to package that module and its tests up for CPAN, and | |
144 | do so. Test it with older perl releases, and fix the problems you find. | |
e50bb9a1 | 145 | |
a393eb28 RGS |
146 | To make a minimal perl distribution, it's useful to look at |
147 | F<t/lib/commonsense.t>. | |
148 | ||
0bdfc961 | 149 | =head2 POSIX memory footprint |
e50bb9a1 | 150 | |
0bdfc961 NC |
151 | Ilya observed that use POSIX; eats memory like there's no tomorrow, and at |
152 | various times worked to cut it down. There is probably still fat to cut out - | |
153 | for example POSIX passes Exporter some very memory hungry data structures. | |
e50bb9a1 | 154 | |
eed36644 NC |
155 | =head2 embed.pl/makedef.pl |
156 | ||
157 | There is a script F<embed.pl> that generates several header files to prefix | |
158 | all of Perl's symbols in a consistent way, to provide some semblance of | |
159 | namespace support in C<C>. Functions are declared in F<embed.fnc>, variables | |
907b3e23 | 160 | in F<interpvar.h>. Quite a few of the functions and variables |
eed36644 NC |
161 | are conditionally declared there, using C<#ifdef>. However, F<embed.pl> |
162 | doesn't understand the C macros, so the rules about which symbols are present | |
163 | when is duplicated in F<makedef.pl>. Writing things twice is bad, m'kay. | |
164 | It would be good to teach C<embed.pl> to understand the conditional | |
165 | compilation, and hence remove the duplication, and the mistakes it has caused. | |
e50bb9a1 | 166 | |
801de10e NC |
167 | =head2 use strict; and AutoLoad |
168 | ||
169 | Currently if you write | |
170 | ||
171 | package Whack; | |
172 | use AutoLoader 'AUTOLOAD'; | |
173 | use strict; | |
174 | 1; | |
175 | __END__ | |
176 | sub bloop { | |
177 | print join (' ', No, strict, here), "!\n"; | |
178 | } | |
179 | ||
180 | then C<use strict;> isn't in force within the autoloaded subroutines. It would | |
181 | be more consistent (and less surprising) to arrange for all lexical pragmas | |
182 | in force at the __END__ block to be in force within each autoloaded subroutine. | |
183 | ||
773b3597 RGS |
184 | There's a similar problem with SelfLoader. |
185 | ||
91d0cbf6 NC |
186 | =head2 profile installman |
187 | ||
188 | The F<installman> script is slow. All it is doing text processing, which we're | |
189 | told is something Perl is good at. So it would be nice to know what it is doing | |
190 | that is taking so much CPU, and where possible address it. | |
191 | ||
c69ca1d4 | 192 | =head2 enable lexical enabling/disabling of individual warnings |
a9ed9b74 JV |
193 | |
194 | Currently, warnings can only be enabled or disabled by category. There | |
195 | are times when it would be useful to quash a single warning, not a | |
196 | whole category. | |
91d0cbf6 | 197 | |
0bdfc961 | 198 | =head1 Tasks that need a little sysadmin-type knowledge |
e50bb9a1 | 199 | |
0bdfc961 NC |
200 | Or if you prefer, tasks that you would learn from, and broaden your skills |
201 | base... | |
e50bb9a1 | 202 | |
cd793d32 | 203 | =head2 make HTML install work |
e50bb9a1 | 204 | |
adebf063 NC |
205 | There is an C<installhtml> target in the Makefile. It's marked as |
206 | "experimental". It would be good to get this tested, make it work reliably, and | |
207 | remove the "experimental" tag. This would include | |
208 | ||
209 | =over 4 | |
210 | ||
211 | =item 1 | |
212 | ||
213 | Checking that cross linking between various parts of the documentation works. | |
214 | In particular that links work between the modules (files with POD in F<lib/>) | |
215 | and the core documentation (files in F<pod/>) | |
216 | ||
217 | =item 2 | |
218 | ||
617eabfa NC |
219 | Work out how to split C<perlfunc> into chunks, preferably one per function |
220 | group, preferably with general case code that could be used elsewhere. | |
221 | Challenges here are correctly identifying the groups of functions that go | |
222 | together, and making the right named external cross-links point to the right | |
223 | page. Things to be aware of are C<-X>, groups such as C<getpwnam> to | |
224 | C<endservent>, two or more C<=items> giving the different parameter lists, such | |
225 | as | |
adebf063 NC |
226 | |
227 | =item substr EXPR,OFFSET,LENGTH,REPLACEMENT | |
adebf063 | 228 | =item substr EXPR,OFFSET,LENGTH |
adebf063 NC |
229 | =item substr EXPR,OFFSET |
230 | ||
231 | and different parameter lists having different meanings. (eg C<select>) | |
232 | ||
233 | =back | |
3a89a73c | 234 | |
0bdfc961 NC |
235 | =head2 compressed man pages |
236 | ||
237 | Be able to install them. This would probably need a configure test to see how | |
238 | the system does compressed man pages (same directory/different directory? | |
239 | same filename/different filename), as well as tweaking the F<installman> script | |
240 | to compress as necessary. | |
241 | ||
30222c0f NC |
242 | =head2 Add a code coverage target to the Makefile |
243 | ||
244 | Make it easy for anyone to run Devel::Cover on the core's tests. The steps | |
245 | to do this manually are roughly | |
246 | ||
247 | =over 4 | |
248 | ||
249 | =item * | |
250 | ||
251 | do a normal C<Configure>, but include Devel::Cover as a module to install | |
f11a3063 | 252 | (see L<INSTALL> for how to do this) |
30222c0f NC |
253 | |
254 | =item * | |
255 | ||
256 | make perl | |
257 | ||
258 | =item * | |
259 | ||
260 | cd t; HARNESS_PERL_SWITCHES=-MDevel::Cover ./perl -I../lib harness | |
261 | ||
262 | =item * | |
263 | ||
264 | Process the resulting Devel::Cover database | |
265 | ||
266 | =back | |
267 | ||
268 | This just give you the coverage of the F<.pm>s. To also get the C level | |
269 | coverage you need to | |
270 | ||
271 | =over 4 | |
272 | ||
273 | =item * | |
274 | ||
275 | Additionally tell C<Configure> to use the appropriate C compiler flags for | |
276 | C<gcov> | |
277 | ||
278 | =item * | |
279 | ||
280 | make perl.gcov | |
281 | ||
282 | (instead of C<make perl>) | |
283 | ||
284 | =item * | |
285 | ||
286 | After running the tests run C<gcov> to generate all the F<.gcov> files. | |
287 | (Including down in the subdirectories of F<ext/> | |
288 | ||
289 | =item * | |
290 | ||
291 | (From the top level perl directory) run C<gcov2perl> on all the C<.gcov> files | |
292 | to get their stats into the cover_db directory. | |
293 | ||
294 | =item * | |
295 | ||
296 | Then process the Devel::Cover database | |
297 | ||
298 | =back | |
299 | ||
300 | It would be good to add a single switch to C<Configure> to specify that you | |
301 | wanted to perform perl level coverage, and another to specify C level | |
302 | coverage, and have C<Configure> and the F<Makefile> do all the right things | |
303 | automatically. | |
304 | ||
02f21748 | 305 | =head2 Make Config.pm cope with differences between built and installed perl |
0bdfc961 NC |
306 | |
307 | Quite often vendors ship a perl binary compiled with their (pay-for) | |
308 | compilers. People install a free compiler, such as gcc. To work out how to | |
309 | build extensions, Perl interrogates C<%Config>, so in this situation | |
310 | C<%Config> describes compilers that aren't there, and extension building | |
311 | fails. This forces people into choosing between re-compiling perl themselves | |
312 | using the compiler they have, or only using modules that the vendor ships. | |
313 | ||
314 | It would be good to find a way teach C<Config.pm> about the installation setup, | |
315 | possibly involving probing at install time or later, so that the C<%Config> in | |
316 | a binary distribution better describes the installed machine, when the | |
317 | installed machine differs from the build machine in some significant way. | |
318 | ||
728f4ecd NC |
319 | =head2 linker specification files |
320 | ||
321 | Some platforms mandate that you provide a list of a shared library's external | |
322 | symbols to the linker, so the core already has the infrastructure in place to | |
323 | do this for generating shared perl libraries. My understanding is that the | |
324 | GNU toolchain can accept an optional linker specification file, and restrict | |
325 | visibility just to symbols declared in that file. It would be good to extend | |
326 | F<makedef.pl> to support this format, and to provide a means within | |
327 | C<Configure> to enable it. This would allow Unix users to test that the | |
328 | export list is correct, and to build a perl that does not pollute the global | |
32d539f5 RU |
329 | namespace with private symbols, and will fail in the same way as msvc or mingw |
330 | builds or when using PERL_DL_NONLAZY=1. | |
728f4ecd | 331 | |
a229ae3b RGS |
332 | =head2 Cross-compile support |
333 | ||
334 | Currently C<Configure> understands C<-Dusecrosscompile> option. This option | |
335 | arranges for building C<miniperl> for TARGET machine, so this C<miniperl> is | |
336 | assumed then to be copied to TARGET machine and used as a replacement of full | |
337 | C<perl> executable. | |
338 | ||
d1307786 | 339 | This could be done little differently. Namely C<miniperl> should be built for |
a229ae3b | 340 | HOST and then full C<perl> with extensions should be compiled for TARGET. |
d1307786 | 341 | This, however, might require extra trickery for %Config: we have one config |
87a942b1 JH |
342 | first for HOST and then another for TARGET. Tools like MakeMaker will be |
343 | mightily confused. Having around two different types of executables and | |
344 | libraries (HOST and TARGET) makes life interesting for Makefiles and | |
345 | shell (and Perl) scripts. There is $Config{run}, normally empty, which | |
346 | can be used as an execution wrapper. Also note that in some | |
347 | cross-compilation/execution environments the HOST and the TARGET do | |
348 | not see the same filesystem(s), the $Config{run} may need to do some | |
349 | file/directory copying back and forth. | |
0bdfc961 | 350 | |
8537f021 RGS |
351 | =head2 roffitall |
352 | ||
353 | Make F<pod/roffitall> be updated by F<pod/buildtoc>. | |
354 | ||
98fca0e8 NC |
355 | =head2 Split "linker" from "compiler" |
356 | ||
357 | Right now, Configure probes for two commands, and sets two variables: | |
358 | ||
359 | =over 4 | |
360 | ||
b91dd380 | 361 | =item * C<cc> (in F<cc.U>) |
98fca0e8 NC |
362 | |
363 | This variable holds the name of a command to execute a C compiler which | |
364 | can resolve multiple global references that happen to have the same | |
365 | name. Usual values are F<cc> and F<gcc>. | |
366 | Fervent ANSI compilers may be called F<c89>. AIX has F<xlc>. | |
367 | ||
b91dd380 | 368 | =item * C<ld> (in F<dlsrc.U>) |
98fca0e8 NC |
369 | |
370 | This variable indicates the program to be used to link | |
371 | libraries for dynamic loading. On some systems, it is F<ld>. | |
372 | On ELF systems, it should be C<$cc>. Mostly, we'll try to respect | |
373 | the hint file setting. | |
374 | ||
375 | =back | |
376 | ||
8d159ec1 NC |
377 | There is an implicit historical assumption from around Perl5.000alpha |
378 | something, that C<$cc> is also the correct command for linking object files | |
379 | together to make an executable. This may be true on Unix, but it's not true | |
380 | on other platforms, and there are a maze of work arounds in other places (such | |
381 | as F<Makefile.SH>) to cope with this. | |
98fca0e8 NC |
382 | |
383 | Ideally, we should create a new variable to hold the name of the executable | |
384 | linker program, probe for it in F<Configure>, and centralise all the special | |
385 | case logic there or in hints files. | |
386 | ||
387 | A small bikeshed issue remains - what to call it, given that C<$ld> is already | |
8d159ec1 NC |
388 | taken (arguably for the wrong thing now, but on SunOS 4.1 it is the command |
389 | for creating dynamically-loadable modules) and C<$link> could be confused with | |
390 | the Unix command line executable of the same name, which does something | |
391 | completely different. Andy Dougherty makes the counter argument "In parrot, I | |
392 | tried to call the command used to link object files and libraries into an | |
393 | executable F<link>, since that's what my vaguely-remembered DOS and VMS | |
394 | experience suggested. I don't think any real confusion has ensued, so it's | |
395 | probably a reasonable name for perl5 to use." | |
98fca0e8 NC |
396 | |
397 | "Alas, I've always worried that introducing it would make things worse, | |
398 | since now the module building utilities would have to look for | |
399 | C<$Config{link}> and institute a fall-back plan if it weren't found." | |
8d159ec1 NC |
400 | Although I can see that as confusing, given that C<$Config{d_link}> is true |
401 | when (hard) links are available. | |
98fca0e8 | 402 | |
75585ce3 SP |
403 | =head2 Configure Windows using PowerShell |
404 | ||
405 | Currently, Windows uses hard-coded config files based to build the | |
406 | config.h for compiling Perl. Makefiles are also hard-coded and need to be | |
407 | hand edited prior to building Perl. While this makes it easy to create a perl.exe | |
408 | that works across multiple Windows versions, being able to accurately | |
409 | configure a perl.exe for a specific Windows versions and VS C++ would be | |
410 | a nice enhancement. With PowerShell available on Windows XP and up, this | |
411 | may now be possible. Step 1 might be to investigate whether this is possible | |
412 | and use this to clean up our current makefile situation. Step 2 would be to | |
413 | see if there would be a way to use our existing metaconfig units to configure a | |
414 | Windows Perl or whether we go in a separate direction and make it so. Of | |
415 | course, we all know what step 3 is. | |
416 | ||
ab45a0fa NC |
417 | =head2 decouple -g and -DDEBUGGING |
418 | ||
419 | Currently F<Configure> automatically adds C<-DDEBUGGING> to the C compiler | |
420 | flags if it spots C<-g> in the optimiser flags. The pre-processor directive | |
eeab323f | 421 | C<DEBUGGING> enables F<perl>'s command line C<-D> options, but in the process |
ab45a0fa NC |
422 | makes F<perl> slower. It would be good to disentangle this logic, so that |
423 | C-level debugging with C<-g> and Perl level debugging with C<-D> can easily | |
424 | be enabled independently. | |
425 | ||
0bdfc961 NC |
426 | =head1 Tasks that need a little C knowledge |
427 | ||
428 | These tasks would need a little C knowledge, but don't need any specific | |
429 | background or experience with XS, or how the Perl interpreter works | |
430 | ||
3d826b29 NC |
431 | =head2 Weed out needless PERL_UNUSED_ARG |
432 | ||
433 | The C code uses the macro C<PERL_UNUSED_ARG> to stop compilers warning about | |
434 | unused arguments. Often the arguments can't be removed, as there is an | |
435 | external constraint that determines the prototype of the function, so this | |
436 | approach is valid. However, there are some cases where C<PERL_UNUSED_ARG> | |
437 | could be removed. Specifically | |
438 | ||
439 | =over 4 | |
440 | ||
441 | =item * | |
442 | ||
443 | The prototypes of (nearly all) static functions can be changed | |
444 | ||
445 | =item * | |
446 | ||
447 | Unused arguments generated by short cut macros are wasteful - the short cut | |
448 | macro used can be changed. | |
449 | ||
450 | =back | |
451 | ||
fbf638cb RGS |
452 | =head2 Modernize the order of directories in @INC |
453 | ||
454 | The way @INC is laid out by default, one cannot upgrade core (dual-life) | |
455 | modules without overwriting files. This causes problems for binary | |
3d14fd97 AD |
456 | package builders. One possible proposal is laid out in this |
457 | message: | |
458 | L<http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/2002-04/msg02380.html>. | |
fbf638cb | 459 | |
bcbaa2d5 RGS |
460 | =head2 -Duse32bit* |
461 | ||
462 | Natively 64-bit systems need neither -Duse64bitint nor -Duse64bitall. | |
463 | On these systems, it might be the default compilation mode, and there | |
464 | is currently no guarantee that passing no use64bitall option to the | |
465 | Configure process will build a 32bit perl. Implementing -Duse32bit* | |
fd2dadea | 466 | options would be nice for perl 5.14. |
bcbaa2d5 | 467 | |
fee0a0f7 | 468 | =head2 Profile Perl - am I hot or not? |
62403a3c | 469 | |
fee0a0f7 NC |
470 | The Perl source code is stable enough that it makes sense to profile it, |
471 | identify and optimise the hotspots. It would be good to measure the | |
472 | performance of the Perl interpreter using free tools such as cachegrind, | |
473 | gprof, and dtrace, and work to reduce the bottlenecks they reveal. | |
474 | ||
475 | As part of this, the idea of F<pp_hot.c> is that it contains the I<hot> ops, | |
476 | the ops that are most commonly used. The idea is that by grouping them, their | |
477 | object code will be adjacent in the executable, so they have a greater chance | |
478 | of already being in the CPU cache (or swapped in) due to being near another op | |
479 | already in use. | |
62403a3c NC |
480 | |
481 | Except that it's not clear if these really are the most commonly used ops. So | |
fee0a0f7 NC |
482 | as part of exercising your skills with coverage and profiling tools you might |
483 | want to determine what ops I<really> are the most commonly used. And in turn | |
484 | suggest evictions and promotions to achieve a better F<pp_hot.c>. | |
62403a3c | 485 | |
91d0cbf6 NC |
486 | One piece of Perl code that might make a good testbed is F<installman>. |
487 | ||
98fed0ad NC |
488 | =head2 Allocate OPs from arenas |
489 | ||
490 | Currently all new OP structures are individually malloc()ed and free()d. | |
491 | All C<malloc> implementations have space overheads, and are now as fast as | |
492 | custom allocates so it would both use less memory and less CPU to allocate | |
493 | the various OP structures from arenas. The SV arena code can probably be | |
494 | re-used for this. | |
495 | ||
539f2c54 JC |
496 | Note that Configuring perl with C<-Accflags=-DPL_OP_SLAB_ALLOC> will use |
497 | Perl_Slab_alloc() to pack optrees into a contiguous block, which is | |
498 | probably superior to the use of OP arenas, esp. from a cache locality | |
499 | standpoint. See L<Profile Perl - am I hot or not?>. | |
500 | ||
a229ae3b | 501 | =head2 Improve win32/wince.c |
0bdfc961 | 502 | |
a229ae3b | 503 | Currently, numerous functions look virtually, if not completely, |
02f21748 | 504 | identical in both C<win32/wince.c> and C<win32/win32.c> files, which can't |
6d71adcd NC |
505 | be good. |
506 | ||
c5b31784 SH |
507 | =head2 Use secure CRT functions when building with VC8 on Win32 |
508 | ||
509 | Visual C++ 2005 (VC++ 8.x) deprecated a number of CRT functions on the basis | |
510 | that they were "unsafe" and introduced differently named secure versions of | |
511 | them as replacements, e.g. instead of writing | |
512 | ||
513 | FILE* f = fopen(__FILE__, "r"); | |
514 | ||
515 | one should now write | |
516 | ||
517 | FILE* f; | |
518 | errno_t err = fopen_s(&f, __FILE__, "r"); | |
519 | ||
520 | Currently, the warnings about these deprecations have been disabled by adding | |
521 | -D_CRT_SECURE_NO_DEPRECATE to the CFLAGS. It would be nice to remove that | |
522 | warning suppressant and actually make use of the new secure CRT functions. | |
523 | ||
524 | There is also a similar issue with POSIX CRT function names like fileno having | |
525 | been deprecated in favour of ISO C++ conformant names like _fileno. These | |
26a6faa8 | 526 | warnings are also currently suppressed by adding -D_CRT_NONSTDC_NO_DEPRECATE. It |
c5b31784 SH |
527 | might be nice to do as Microsoft suggest here too, although, unlike the secure |
528 | functions issue, there is presumably little or no benefit in this case. | |
529 | ||
038ae9a4 SH |
530 | =head2 Fix POSIX::access() and chdir() on Win32 |
531 | ||
532 | These functions currently take no account of DACLs and therefore do not behave | |
533 | correctly in situations where access is restricted by DACLs (as opposed to the | |
534 | read-only attribute). | |
535 | ||
536 | Furthermore, POSIX::access() behaves differently for directories having the | |
537 | read-only attribute set depending on what CRT library is being used. For | |
538 | example, the _access() function in the VC6 and VC7 CRTs (wrongly) claim that | |
539 | such directories are not writable, whereas in fact all directories are writable | |
540 | unless access is denied by DACLs. (In the case of directories, the read-only | |
541 | attribute actually only means that the directory cannot be deleted.) This CRT | |
542 | bug is fixed in the VC8 and VC9 CRTs (but, of course, the directory may still | |
543 | not actually be writable if access is indeed denied by DACLs). | |
544 | ||
545 | For the chdir() issue, see ActiveState bug #74552: | |
546 | http://bugs.activestate.com/show_bug.cgi?id=74552 | |
547 | ||
548 | Therefore, DACLs should be checked both for consistency across CRTs and for | |
549 | the correct answer. | |
550 | ||
551 | (Note that perl's -w operator should not be modified to check DACLs. It has | |
552 | been written so that it reflects the state of the read-only attribute, even | |
553 | for directories (whatever CRT is being used), for symmetry with chmod().) | |
554 | ||
16815324 NC |
555 | =head2 strcat(), strcpy(), strncat(), strncpy(), sprintf(), vsprintf() |
556 | ||
557 | Maybe create a utility that checks after each libperl.a creation that | |
558 | none of the above (nor sprintf(), vsprintf(), or *SHUDDER* gets()) | |
559 | ever creep back to libperl.a. | |
560 | ||
561 | nm libperl.a | ./miniperl -alne '$o = $F[0] if /:$/; print "$o $F[1]" if $F[0] eq "U" && $F[1] =~ /^(?:strn?c(?:at|py)|v?sprintf|gets)$/' | |
562 | ||
563 | Note, of course, that this will only tell whether B<your> platform | |
564 | is using those naughty interfaces. | |
565 | ||
de96509d JH |
566 | =head2 -D_FORTIFY_SOURCE=2, -fstack-protector |
567 | ||
568 | Recent glibcs support C<-D_FORTIFY_SOURCE=2> and recent gcc | |
569 | (4.1 onwards?) supports C<-fstack-protector>, both of which give | |
570 | protection against various kinds of buffer overflow problems. | |
571 | These should probably be used for compiling Perl whenever available, | |
572 | Configure and/or hints files should be adjusted to probe for the | |
573 | availability of these features and enable them as appropriate. | |
16815324 | 574 | |
8964cfe0 NC |
575 | =head2 Arenas for GPs? For MAGIC? |
576 | ||
577 | C<struct gp> and C<struct magic> are both currently allocated by C<malloc>. | |
578 | It might be a speed or memory saving to change to using arenas. Or it might | |
579 | not. It would need some suitable benchmarking first. In particular, C<GP>s | |
580 | can probably be changed with minimal compatibility impact (probably nothing | |
581 | outside of the core, or even outside of F<gv.c> allocates them), but they | |
582 | probably aren't allocated/deallocated often enough for a speed saving. Whereas | |
583 | C<MAGIC> is allocated/deallocated more often, but in turn, is also something | |
584 | more externally visible, so changing the rules here may bite external code. | |
585 | ||
3880c8ec NC |
586 | =head2 Shared arenas |
587 | ||
588 | Several SV body structs are now the same size, notably PVMG and PVGV, PVAV and | |
589 | PVHV, and PVCV and PVFM. It should be possible to allocate and return same | |
590 | sized bodies from the same actual arena, rather than maintaining one arena for | |
591 | each. This could save 4-6K per thread, of memory no longer tied up in the | |
592 | not-yet-allocated part of an arena. | |
593 | ||
8964cfe0 | 594 | |
6d71adcd NC |
595 | =head1 Tasks that need a knowledge of XS |
596 | ||
597 | These tasks would need C knowledge, and roughly the level of knowledge of | |
598 | the perl API that comes from writing modules that use XS to interface to | |
599 | C. | |
600 | ||
e851c105 DG |
601 | =head2 Write an XS cookbook |
602 | ||
603 | Create pod/perlxscookbook.pod with short, task-focused 'recipes' in XS that | |
604 | demonstrate common tasks and good practices. (Some of these might be | |
605 | extracted from perlguts.) The target audience should be XS novices, who need | |
606 | more examples than perlguts but something less overwhelming than perlapi. | |
607 | Recipes should provide "one pretty good way to do it" instead of TIMTOWTDI. | |
608 | ||
5b7d14ff DG |
609 | Rather than focusing on interfacing Perl to C libraries, such a cookbook |
610 | should probably focus on how to optimize Perl routines by re-writing them | |
611 | in XS. This will likely be more motivating to those who mostly work in | |
612 | Perl but are looking to take the next step into XS. | |
613 | ||
614 | Deconstructing and explaining some simpler XS modules could be one way to | |
615 | bootstrap a cookbook. (List::Util? Class::XSAccessor? Tree::Ternary_XS?) | |
616 | Another option could be deconstructing the implementation of some simpler | |
617 | functions in op.c. | |
618 | ||
05fb4e20 NC |
619 | =head2 Allow XSUBs to inline themselves as OPs |
620 | ||
621 | For a simple XSUB, often the subroutine dispatch takes more time than the | |
622 | XSUB itself. The tokeniser already has the ability to inline constant | |
623 | subroutines - it would be good to provide a way to inline other subroutines. | |
624 | ||
625 | Specifically, simplest approach looks to be to allow an XSUB to provide an | |
626 | alternative implementation of itself as a custom OP. A new flag bit in | |
627 | C<CvFLAGS()> would signal to the peephole optimiser to take an optree | |
628 | such as this: | |
629 | ||
630 | b <@> leave[1 ref] vKP/REFC ->(end) | |
631 | 1 <0> enter ->2 | |
632 | 2 <;> nextstate(main 1 -e:1) v:{ ->3 | |
633 | a <2> sassign vKS/2 ->b | |
634 | 8 <1> entersub[t2] sKS/TARG,1 ->9 | |
635 | - <1> ex-list sK ->8 | |
636 | 3 <0> pushmark s ->4 | |
637 | 4 <$> const(IV 1) sM ->5 | |
638 | 6 <1> rv2av[t1] lKM/1 ->7 | |
639 | 5 <$> gv(*a) s ->6 | |
640 | - <1> ex-rv2cv sK ->- | |
641 | 7 <$> gv(*x) s/EARLYCV ->8 | |
642 | - <1> ex-rv2sv sKRM*/1 ->a | |
643 | 9 <$> gvsv(*b) s ->a | |
644 | ||
645 | perform the symbol table lookup of C<rv2cv> and C<gv(*x)>, locate the | |
646 | pointer to the custom OP that provides the direct implementation, and re- | |
647 | write the optree something like: | |
648 | ||
649 | b <@> leave[1 ref] vKP/REFC ->(end) | |
650 | 1 <0> enter ->2 | |
651 | 2 <;> nextstate(main 1 -e:1) v:{ ->3 | |
652 | a <2> sassign vKS/2 ->b | |
653 | 7 <1> custom_x -> 8 | |
654 | - <1> ex-list sK ->7 | |
655 | 3 <0> pushmark s ->4 | |
656 | 4 <$> const(IV 1) sM ->5 | |
657 | 6 <1> rv2av[t1] lKM/1 ->7 | |
658 | 5 <$> gv(*a) s ->6 | |
659 | - <1> ex-rv2cv sK ->- | |
660 | - <$> ex-gv(*x) s/EARLYCV ->7 | |
661 | - <1> ex-rv2sv sKRM*/1 ->a | |
662 | 8 <$> gvsv(*b) s ->a | |
663 | ||
664 | I<i.e.> the C<gv(*)> OP has been nulled and spliced out of the execution | |
665 | path, and the C<entersub> OP has been replaced by the custom op. | |
666 | ||
667 | This approach should provide a measurable speed up to simple XSUBs inside | |
668 | tight loops. Initially one would have to write the OP alternative | |
669 | implementation by hand, but it's likely that this should be reasonably | |
670 | straightforward for the type of XSUB that would benefit the most. Longer | |
671 | term, once the run-time implementation is proven, it should be possible to | |
672 | progressively update ExtUtils::ParseXS to generate OP implementations for | |
673 | some XSUBs. | |
674 | ||
318bf708 NC |
675 | =head2 Remove the use of SVs as temporaries in dump.c |
676 | ||
677 | F<dump.c> contains debugging routines to dump out the contains of perl data | |
678 | structures, such as C<SV>s, C<AV>s and C<HV>s. Currently, the dumping code | |
679 | B<uses> C<SV>s for its temporary buffers, which was a logical initial | |
680 | implementation choice, as they provide ready made memory handling. | |
681 | ||
682 | However, they also lead to a lot of confusion when it happens that what you're | |
683 | trying to debug is seen by the code in F<dump.c>, correctly or incorrectly, as | |
684 | a temporary scalar it can use for a temporary buffer. It's also not possible | |
685 | to dump scalars before the interpreter is properly set up, such as during | |
686 | ithreads cloning. It would be good to progressively replace the use of scalars | |
687 | as string accumulation buffers with something much simpler, directly allocated | |
688 | by C<malloc>. The F<dump.c> code is (or should be) only producing 7 bit | |
689 | US-ASCII, so output character sets are not an issue. | |
690 | ||
691 | Producing and proving an internal simple buffer allocation would make it easier | |
692 | to re-write the internals of the PerlIO subsystem to avoid using C<SV>s for | |
693 | B<its> buffers, use of which can cause problems similar to those of F<dump.c>, | |
694 | at similar times. | |
695 | ||
5d96f598 NC |
696 | =head2 safely supporting POSIX SA_SIGINFO |
697 | ||
698 | Some years ago Jarkko supplied patches to provide support for the POSIX | |
699 | SA_SIGINFO feature in Perl, passing the extra data to the Perl signal handler. | |
700 | ||
701 | Unfortunately, it only works with "unsafe" signals, because under safe | |
702 | signals, by the time Perl gets to run the signal handler, the extra | |
703 | information has been lost. Moreover, it's not easy to store it somewhere, | |
704 | as you can't call mutexs, or do anything else fancy, from inside a signal | |
705 | handler. | |
706 | ||
707 | So it strikes me that we could provide safe SA_SIGINFO support | |
708 | ||
709 | =over 4 | |
710 | ||
711 | =item 1 | |
712 | ||
713 | Provide global variables for two file descriptors | |
714 | ||
715 | =item 2 | |
716 | ||
717 | When the first request is made via C<sigaction> for C<SA_SIGINFO>, create a | |
718 | pipe, store the reader in one, the writer in the other | |
719 | ||
720 | =item 3 | |
721 | ||
722 | In the "safe" signal handler (C<Perl_csighandler()>/C<S_raise_signal()>), if | |
723 | the C<siginfo_t> pointer non-C<NULL>, and the writer file handle is open, | |
724 | ||
725 | =over 8 | |
726 | ||
727 | =item 1 | |
728 | ||
729 | serialise signal number, C<struct siginfo_t> (or at least the parts we care | |
730 | about) into a small auto char buff | |
731 | ||
732 | =item 2 | |
733 | ||
734 | C<write()> that (non-blocking) to the writer fd | |
735 | ||
736 | =over 12 | |
737 | ||
738 | =item 1 | |
739 | ||
740 | if it writes 100%, flag the signal in a counter of "signals on the pipe" akin | |
741 | to the current per-signal-number counts | |
742 | ||
743 | =item 2 | |
744 | ||
745 | if it writes 0%, assume the pipe is full. Flag the data as lost? | |
746 | ||
747 | =item 3 | |
748 | ||
749 | if it writes partially, croak a panic, as your OS is broken. | |
750 | ||
751 | =back | |
752 | ||
753 | =back | |
754 | ||
755 | =item 4 | |
756 | ||
757 | in the regular C<PERL_ASYNC_CHECK()> processing, if there are "signals on | |
758 | the pipe", read the data out, deserialise, build the Perl structures on | |
759 | the stack (code in C<Perl_sighandler()>, the "unsafe" handler), and call as | |
760 | usual. | |
761 | ||
762 | =back | |
763 | ||
764 | I think that this gets us decent C<SA_SIGINFO> support, without the current risk | |
765 | of running Perl code inside the signal handler context. (With all the dangers | |
766 | of things like C<malloc> corruption that that currently offers us) | |
767 | ||
768 | For more information see the thread starting with this message: | |
769 | http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/2008-03/msg00305.html | |
770 | ||
6d71adcd NC |
771 | =head2 autovivification |
772 | ||
773 | Make all autovivification consistent w.r.t LVALUE/RVALUE and strict/no strict; | |
774 | ||
775 | This task is incremental - even a little bit of work on it will help. | |
776 | ||
777 | =head2 Unicode in Filenames | |
778 | ||
779 | chdir, chmod, chown, chroot, exec, glob, link, lstat, mkdir, open, | |
780 | opendir, qx, readdir, readlink, rename, rmdir, stat, symlink, sysopen, | |
781 | system, truncate, unlink, utime, -X. All these could potentially accept | |
782 | Unicode filenames either as input or output (and in the case of system | |
783 | and qx Unicode in general, as input or output to/from the shell). | |
784 | Whether a filesystem - an operating system pair understands Unicode in | |
785 | filenames varies. | |
786 | ||
787 | Known combinations that have some level of understanding include | |
788 | Microsoft NTFS, Apple HFS+ (In Mac OS 9 and X) and Apple UFS (in Mac | |
789 | OS X), NFS v4 is rumored to be Unicode, and of course Plan 9. How to | |
790 | create Unicode filenames, what forms of Unicode are accepted and used | |
791 | (UCS-2, UTF-16, UTF-8), what (if any) is the normalization form used, | |
792 | and so on, varies. Finding the right level of interfacing to Perl | |
793 | requires some thought. Remember that an OS does not implicate a | |
794 | filesystem. | |
795 | ||
796 | (The Windows -C command flag "wide API support" has been at least | |
797 | temporarily retired in 5.8.1, and the -C has been repurposed, see | |
798 | L<perlrun>.) | |
799 | ||
87a942b1 JH |
800 | Most probably the right way to do this would be this: |
801 | L</"Virtualize operating system access">. | |
802 | ||
6d71adcd NC |
803 | =head2 Unicode in %ENV |
804 | ||
805 | Currently the %ENV entries are always byte strings. | |
87a942b1 | 806 | See L</"Virtualize operating system access">. |
6d71adcd | 807 | |
1f2e7916 JD |
808 | =head2 Unicode and glob() |
809 | ||
810 | Currently glob patterns and filenames returned from File::Glob::glob() | |
87a942b1 | 811 | are always byte strings. See L</"Virtualize operating system access">. |
1f2e7916 | 812 | |
6d71adcd NC |
813 | =head2 use less 'memory' |
814 | ||
815 | Investigate trade offs to switch out perl's choices on memory usage. | |
816 | Particularly perl should be able to give memory back. | |
817 | ||
818 | This task is incremental - even a little bit of work on it will help. | |
819 | ||
820 | =head2 Re-implement C<:unique> in a way that is actually thread-safe | |
821 | ||
822 | The old implementation made bad assumptions on several levels. A good 90% | |
823 | solution might be just to make C<:unique> work to share the string buffer | |
824 | of SvPVs. That way large constant strings can be shared between ithreads, | |
825 | such as the configuration information in F<Config>. | |
826 | ||
827 | =head2 Make tainting consistent | |
828 | ||
829 | Tainting would be easier to use if it didn't take documented shortcuts and | |
830 | allow taint to "leak" everywhere within an expression. | |
831 | ||
832 | =head2 readpipe(LIST) | |
833 | ||
834 | system() accepts a LIST syntax (and a PROGRAM LIST syntax) to avoid | |
835 | running a shell. readpipe() (the function behind qx//) could be similarly | |
836 | extended. | |
837 | ||
6d71adcd NC |
838 | =head2 Audit the code for destruction ordering assumptions |
839 | ||
840 | Change 25773 notes | |
841 | ||
842 | /* Need to check SvMAGICAL, as during global destruction it may be that | |
843 | AvARYLEN(av) has been freed before av, and hence the SvANY() pointer | |
844 | is now part of the linked list of SV heads, rather than pointing to | |
845 | the original body. */ | |
846 | /* FIXME - audit the code for other bugs like this one. */ | |
847 | ||
848 | adding the C<SvMAGICAL> check to | |
849 | ||
850 | if (AvARYLEN(av) && SvMAGICAL(AvARYLEN(av))) { | |
851 | MAGIC *mg = mg_find (AvARYLEN(av), PERL_MAGIC_arylen); | |
852 | ||
853 | Go through the core and look for similar assumptions that SVs have particular | |
854 | types, as all bets are off during global destruction. | |
855 | ||
749904bf JH |
856 | =head2 Extend PerlIO and PerlIO::Scalar |
857 | ||
858 | PerlIO::Scalar doesn't know how to truncate(). Implementing this | |
859 | would require extending the PerlIO vtable. | |
860 | ||
861 | Similarly the PerlIO vtable doesn't know about formats (write()), or | |
862 | about stat(), or chmod()/chown(), utime(), or flock(). | |
863 | ||
864 | (For PerlIO::Scalar it's hard to see what e.g. mode bits or ownership | |
865 | would mean.) | |
866 | ||
867 | PerlIO doesn't do directories or symlinks, either: mkdir(), rmdir(), | |
868 | opendir(), closedir(), seekdir(), rewinddir(), glob(); symlink(), | |
869 | readlink(). | |
870 | ||
94da6c29 JH |
871 | See also L</"Virtualize operating system access">. |
872 | ||
3236f110 NC |
873 | =head2 -C on the #! line |
874 | ||
875 | It should be possible to make -C work correctly if found on the #! line, | |
876 | given that all perl command line options are strict ASCII, and -C changes | |
877 | only the interpretation of non-ASCII characters, and not for the script file | |
878 | handle. To make it work needs some investigation of the ordering of function | |
879 | calls during startup, and (by implication) a bit of tweaking of that order. | |
880 | ||
d6c1e11f JH |
881 | =head2 Organize error messages |
882 | ||
883 | Perl's diagnostics (error messages, see L<perldiag>) could use | |
a8d0aeb9 | 884 | reorganizing and formalizing so that each error message has its |
d6c1e11f JH |
885 | stable-for-all-eternity unique id, categorized by severity, type, and |
886 | subsystem. (The error messages would be listed in a datafile outside | |
c4bd451b CB |
887 | of the Perl source code, and the source code would only refer to the |
888 | messages by the id.) This clean-up and regularizing should apply | |
d6c1e11f JH |
889 | for all croak() messages. |
890 | ||
891 | This would enable all sorts of things: easier translation/localization | |
892 | of the messages (though please do keep in mind the caveats of | |
893 | L<Locale::Maketext> about too straightforward approaches to | |
894 | translation), filtering by severity, and instead of grepping for a | |
895 | particular error message one could look for a stable error id. (Of | |
896 | course, changing the error messages by default would break all the | |
897 | existing software depending on some particular error message...) | |
898 | ||
899 | This kind of functionality is known as I<message catalogs>. Look for | |
900 | inspiration for example in the catgets() system, possibly even use it | |
901 | if available-- but B<only> if available, all platforms will B<not> | |
de96509d | 902 | have catgets(). |
d6c1e11f JH |
903 | |
904 | For the really pure at heart, consider extending this item to cover | |
905 | also the warning messages (see L<perllexwarn>, C<warnings.pl>). | |
3236f110 | 906 | |
0bdfc961 | 907 | =head1 Tasks that need a knowledge of the interpreter |
3298bd4d | 908 | |
0bdfc961 NC |
909 | These tasks would need C knowledge, and knowledge of how the interpreter works, |
910 | or a willingness to learn. | |
3298bd4d | 911 | |
10517af5 JD |
912 | =head2 forbid labels with keyword names |
913 | ||
914 | Currently C<goto keyword> "computes" the label value: | |
915 | ||
916 | $ perl -e 'goto print' | |
917 | Can't find label 1 at -e line 1. | |
918 | ||
343c8006 JD |
919 | It is controversial if the right way to avoid the confusion is to forbid |
920 | labels with keyword names, or if it would be better to always treat | |
921 | bareword expressions after a "goto" as a label and never as a keyword. | |
10517af5 | 922 | |
de6375e3 RGS |
923 | =head2 truncate() prototype |
924 | ||
925 | The prototype of truncate() is currently C<$$>. It should probably | |
926 | be C<*$> instead. (This is changed in F<opcode.pl>) | |
927 | ||
2d0587d8 RGS |
928 | =head2 decapsulation of smart match argument |
929 | ||
930 | Currently C<$foo ~~ $object> will die with the message "Smart matching a | |
931 | non-overloaded object breaks encapsulation". It would be nice to allow | |
c69ca1d4 | 932 | to bypass this by using explicitly the syntax C<$foo ~~ %$object> or |
2d0587d8 RGS |
933 | C<$foo ~~ @$object>. |
934 | ||
565590b5 NC |
935 | =head2 error reporting of [$a ; $b] |
936 | ||
937 | Using C<;> inside brackets is a syntax error, and we don't propose to change | |
938 | that by giving it any meaning. However, it's not reported very helpfully: | |
939 | ||
940 | $ perl -e '$a = [$b; $c];' | |
941 | syntax error at -e line 1, near "$b;" | |
942 | syntax error at -e line 1, near "$c]" | |
943 | Execution of -e aborted due to compilation errors. | |
944 | ||
945 | It should be possible to hook into the tokeniser or the lexer, so that when a | |
946 | C<;> is parsed where it is not legal as a statement terminator (ie inside | |
947 | C<{}> used as a hashref, C<[]> or C<()>) it issues an error something like | |
948 | I<';' isn't legal inside an expression - if you need multiple statements use a | |
949 | do {...} block>. See the thread starting at | |
950 | http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/2008-09/msg00573.html | |
951 | ||
718140ec NC |
952 | =head2 lexicals used only once |
953 | ||
954 | This warns: | |
955 | ||
956 | $ perl -we '$pie = 42' | |
957 | Name "main::pie" used only once: possible typo at -e line 1. | |
958 | ||
959 | This does not: | |
960 | ||
961 | $ perl -we 'my $pie = 42' | |
962 | ||
963 | Logically all lexicals used only once should warn, if the user asks for | |
d6f4ea2e SP |
964 | warnings. An unworked RT ticket (#5087) has been open for almost seven |
965 | years for this discrepancy. | |
718140ec | 966 | |
a3d15f9a RGS |
967 | =head2 UTF-8 revamp |
968 | ||
85c006b6 KW |
969 | The handling of Unicode is unclean in many places. In the regex engine |
970 | there are especially many problems. The swash data structure could be | |
971 | replaced my something better. Inversion lists and maps are likely | |
972 | candidates. The whole Unicode database could be placed in-core for a | |
973 | huge speed-up. Only minimal work was done on the optimizer when utf8 | |
974 | was added, with the result that the synthetic start class often will | |
975 | fail to narrow down the possible choices when given non-Latin1 input. | |
a3d15f9a RGS |
976 | |
977 | =head2 Properly Unicode safe tokeniser and pads. | |
978 | ||
979 | The tokeniser isn't actually very UTF-8 clean. C<use utf8;> is a hack - | |
980 | variable names are stored in stashes as raw bytes, without the utf-8 flag | |
981 | set. The pad API only takes a C<char *> pointer, so that's all bytes too. The | |
982 | tokeniser ignores the UTF-8-ness of C<PL_rsfp>, or any SVs returned from | |
983 | source filters. All this could be fixed. | |
984 | ||
636e63cb NC |
985 | =head2 state variable initialization in list context |
986 | ||
987 | Currently this is illegal: | |
988 | ||
989 | state ($a, $b) = foo(); | |
990 | ||
a2874905 | 991 | In Perl 6, C<state ($a) = foo();> and C<(state $a) = foo();> have different |
a8d0aeb9 | 992 | semantics, which is tricky to implement in Perl 5 as currently they produce |
a2874905 | 993 | the same opcode trees. The Perl 6 design is firm, so it would be good to |
a8d0aeb9 | 994 | implement the necessary code in Perl 5. There are comments in |
a2874905 NC |
995 | C<Perl_newASSIGNOP()> that show the code paths taken by various assignment |
996 | constructions involving state variables. | |
636e63cb | 997 | |
4fedb12c RGS |
998 | =head2 Implement $value ~~ 0 .. $range |
999 | ||
1000 | It would be nice to extend the syntax of the C<~~> operator to also | |
1001 | understand numeric (and maybe alphanumeric) ranges. | |
a393eb28 RGS |
1002 | |
1003 | =head2 A does() built-in | |
1004 | ||
1005 | Like ref(), only useful. It would call the C<DOES> method on objects; it | |
1006 | would also tell whether something can be dereferenced as an | |
1007 | array/hash/etc., or used as a regexp, etc. | |
1008 | L<http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/2007-03/msg00481.html> | |
1009 | ||
1010 | =head2 Tied filehandles and write() don't mix | |
1011 | ||
1012 | There is no method on tied filehandles to allow them to be called back by | |
1013 | formats. | |
4fedb12c | 1014 | |
53967bb9 RGS |
1015 | =head2 Propagate compilation hints to the debugger |
1016 | ||
1017 | Currently a debugger started with -dE on the command-line doesn't see the | |
1018 | features enabled by -E. More generally hints (C<$^H> and C<%^H>) aren't | |
1019 | propagated to the debugger. Probably it would be a good thing to propagate | |
1020 | hints from the innermost non-C<DB::> scope: this would make code eval'ed | |
1021 | in the debugger see the features (and strictures, etc.) currently in | |
1022 | scope. | |
1023 | ||
d10fc472 | 1024 | =head2 Attach/detach debugger from running program |
1626a787 | 1025 | |
cd793d32 NC |
1026 | The old perltodo notes "With C<gdb>, you can attach the debugger to a running |
1027 | program if you pass the process ID. It would be good to do this with the Perl | |
0bdfc961 NC |
1028 | debugger on a running Perl program, although I'm not sure how it would be |
1029 | done." ssh and screen do this with named pipes in /tmp. Maybe we can too. | |
1626a787 | 1030 | |
0bdfc961 NC |
1031 | =head2 LVALUE functions for lists |
1032 | ||
1033 | The old perltodo notes that lvalue functions don't work for list or hash | |
1034 | slices. This would be good to fix. | |
1035 | ||
0bdfc961 NC |
1036 | =head2 regexp optimiser optional |
1037 | ||
1038 | The regexp optimiser is not optional. It should configurable to be, to allow | |
1039 | its performance to be measured, and its bugs to be easily demonstrated. | |
1040 | ||
ef36c6a7 RGS |
1041 | =head2 C</w> regex modifier |
1042 | ||
1043 | That flag would enable to match whole words, and also to interpolate | |
1044 | arrays as alternations. With it, C</P/w> would be roughly equivalent to: | |
1045 | ||
1046 | do { local $"='|'; /\b(?:P)\b/ } | |
1047 | ||
1048 | See L<http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/2007-01/msg00400.html> | |
1049 | for the discussion. | |
1050 | ||
0bdfc961 NC |
1051 | =head2 optional optimizer |
1052 | ||
1053 | Make the peephole optimizer optional. Currently it performs two tasks as | |
1054 | it walks the optree - genuine peephole optimisations, and necessary fixups of | |
1055 | ops. It would be good to find an efficient way to switch out the | |
1056 | optimisations whilst keeping the fixups. | |
1057 | ||
1058 | =head2 You WANT *how* many | |
1059 | ||
1060 | Currently contexts are void, scalar and list. split has a special mechanism in | |
1061 | place to pass in the number of return values wanted. It would be useful to | |
1062 | have a general mechanism for this, backwards compatible and little speed hit. | |
1063 | This would allow proposals such as short circuiting sort to be implemented | |
1064 | as a module on CPAN. | |
1065 | ||
1066 | =head2 lexical aliases | |
1067 | ||
1068 | Allow lexical aliases (maybe via the syntax C<my \$alias = \$foo>. | |
1069 | ||
1070 | =head2 entersub XS vs Perl | |
1071 | ||
1072 | At the moment pp_entersub is huge, and has code to deal with entering both | |
1073 | perl and XS subroutines. Subroutine implementations rarely change between | |
1074 | perl and XS at run time, so investigate using 2 ops to enter subs (one for | |
1075 | XS, one for perl) and swap between if a sub is redefined. | |
2810d901 | 1076 | |
de535794 | 1077 | =head2 Self-ties |
2810d901 | 1078 | |
de535794 | 1079 | Self-ties are currently illegal because they caused too many segfaults. Maybe |
a8d0aeb9 | 1080 | the causes of these could be tracked down and self-ties on all types |
de535794 | 1081 | reinstated. |
0bdfc961 NC |
1082 | |
1083 | =head2 Optimize away @_ | |
1084 | ||
1085 | The old perltodo notes "Look at the "reification" code in C<av.c>". | |
1086 | ||
87a942b1 JH |
1087 | =head2 Virtualize operating system access |
1088 | ||
1089 | Implement a set of "vtables" that virtualizes operating system access | |
1090 | (open(), mkdir(), unlink(), readdir(), getenv(), etc.) At the very | |
1091 | least these interfaces should take SVs as "name" arguments instead of | |
1092 | bare char pointers; probably the most flexible and extensible way | |
e1a3d5d1 JH |
1093 | would be for the Perl-facing interfaces to accept HVs. The system |
1094 | needs to be per-operating-system and per-file-system | |
1095 | hookable/filterable, preferably both from XS and Perl level | |
87a942b1 JH |
1096 | (L<perlport/"Files and Filesystems"> is good reading at this point, |
1097 | in fact, all of L<perlport> is.) | |
1098 | ||
e1a3d5d1 JH |
1099 | This has actually already been implemented (but only for Win32), |
1100 | take a look at F<iperlsys.h> and F<win32/perlhost.h>. While all Win32 | |
1101 | variants go through a set of "vtables" for operating system access, | |
e1020413 | 1102 | non-Win32 systems currently go straight for the POSIX/Unix-style |
e1a3d5d1 JH |
1103 | system/library call. Similar system as for Win32 should be |
1104 | implemented for all platforms. The existing Win32 implementation | |
1105 | probably does not need to survive alongside this proposed new | |
1106 | implementation, the approaches could be merged. | |
87a942b1 JH |
1107 | |
1108 | What would this give us? One often-asked-for feature this would | |
94da6c29 JH |
1109 | enable is using Unicode for filenames, and other "names" like %ENV, |
1110 | usernames, hostnames, and so forth. | |
1111 | (See L<perlunicode/"When Unicode Does Not Happen">.) | |
1112 | ||
1113 | But this kind of virtualization would also allow for things like | |
1114 | virtual filesystems, virtual networks, and "sandboxes" (though as long | |
1115 | as dynamic loading of random object code is allowed, not very safe | |
1116 | sandboxes since external code of course know not of Perl's vtables). | |
1117 | An example of a smaller "sandbox" is that this feature can be used to | |
1118 | implement per-thread working directories: Win32 already does this. | |
1119 | ||
1120 | See also L</"Extend PerlIO and PerlIO::Scalar">. | |
87a942b1 | 1121 | |
ac6197af NC |
1122 | =head2 Investigate PADTMP hash pessimisation |
1123 | ||
9a2f2e6b | 1124 | The peephole optimiser converts constants used for hash key lookups to shared |
057163d7 | 1125 | hash key scalars. Under ithreads, something is undoing this work. |
ac6197af NC |
1126 | See http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/2007-09/msg00793.html |
1127 | ||
057163d7 NC |
1128 | =head2 Store the current pad in the OP slab allocator |
1129 | ||
1130 | =for clarification | |
1131 | I hope that I got that "current pad" part correct | |
1132 | ||
1133 | Currently we leak ops in various cases of parse failure. I suggested that we | |
1134 | could solve this by always using the op slab allocator, and walking it to | |
1135 | free ops. Dave comments that as some ops are already freed during optree | |
1136 | creation one would have to mark which ops are freed, and not double free them | |
1137 | when walking the slab. He notes that one problem with this is that for some ops | |
1138 | you have to know which pad was current at the time of allocation, which does | |
1139 | change. I suggested storing a pointer to the current pad in the memory allocated | |
1140 | for the slab, and swapping to a new slab each time the pad changes. Dave thinks | |
1141 | that this would work. | |
1142 | ||
52960e22 JC |
1143 | =head2 repack the optree |
1144 | ||
1145 | Repacking the optree after execution order is determined could allow | |
057163d7 NC |
1146 | removal of NULL ops, and optimal ordering of OPs with respect to cache-line |
1147 | filling. The slab allocator could be reused for this purpose. I think that | |
1148 | the best way to do this is to make it an optional step just before the | |
1149 | completed optree is attached to anything else, and to use the slab allocator | |
1150 | unchanged, so that freeing ops is identical whether or not this step runs. | |
1151 | Note that the slab allocator allocates ops downwards in memory, so one would | |
1152 | have to actually "allocate" the ops in reverse-execution order to get them | |
1153 | contiguous in memory in execution order. | |
1154 | ||
1155 | See http://www.nntp.perl.org/group/perl.perl5.porters/2007/12/msg131975.html | |
1156 | ||
1157 | Note that running this copy, and then freeing all the old location ops would | |
1158 | cause their slabs to be freed, which would eliminate possible memory wastage if | |
1159 | the previous suggestion is implemented, and we swap slabs more frequently. | |
52960e22 | 1160 | |
12e06b6f NC |
1161 | =head2 eliminate incorrect line numbers in warnings |
1162 | ||
1163 | This code | |
1164 | ||
1165 | use warnings; | |
1166 | my $undef; | |
1167 | ||
1168 | if ($undef == 3) { | |
1169 | } elsif ($undef == 0) { | |
1170 | } | |
1171 | ||
18a16cc5 | 1172 | used to produce this output: |
12e06b6f NC |
1173 | |
1174 | Use of uninitialized value in numeric eq (==) at wrong.pl line 4. | |
1175 | Use of uninitialized value in numeric eq (==) at wrong.pl line 4. | |
1176 | ||
18a16cc5 NC |
1177 | where the line of the second warning was misreported - it should be line 5. |
1178 | Rafael fixed this - the problem arose because there was no nextstate OP | |
1179 | between the execution of the C<if> and the C<elsif>, hence C<PL_curcop> still | |
1180 | reports that the currently executing line is line 4. The solution was to inject | |
1181 | a nextstate OPs for each C<elsif>, although it turned out that the nextstate | |
1182 | OP needed to be a nulled OP, rather than a live nextstate OP, else other line | |
1183 | numbers became misreported. (Jenga!) | |
12e06b6f NC |
1184 | |
1185 | The problem is more general than C<elsif> (although the C<elsif> case is the | |
1186 | most common and the most confusing). Ideally this code | |
1187 | ||
1188 | use warnings; | |
1189 | my $undef; | |
1190 | ||
1191 | my $a = $undef + 1; | |
1192 | my $b | |
1193 | = $undef | |
1194 | + 1; | |
1195 | ||
1196 | would produce this output | |
1197 | ||
1198 | Use of uninitialized value $undef in addition (+) at wrong.pl line 4. | |
1199 | Use of uninitialized value $undef in addition (+) at wrong.pl line 7. | |
1200 | ||
1201 | (rather than lines 4 and 5), but this would seem to require every OP to carry | |
1202 | (at least) line number information. | |
1203 | ||
1204 | What might work is to have an optional line number in memory just before the | |
1205 | BASEOP structure, with a flag bit in the op to say whether it's present. | |
1206 | Initially during compile every OP would carry its line number. Then add a late | |
1207 | pass to the optimiser (potentially combined with L</repack the optree>) which | |
1208 | looks at the two ops on every edge of the graph of the execution path. If | |
1209 | the line number changes, flags the destination OP with this information. | |
1210 | Once all paths are traced, replace every op with the flag with a | |
1211 | nextstate-light op (that just updates C<PL_curcop>), which in turn then passes | |
1212 | control on to the true op. All ops would then be replaced by variants that | |
1213 | do not store the line number. (Which, logically, why it would work best in | |
1214 | conjunction with L</repack the optree>, as that is already copying/reallocating | |
1215 | all the OPs) | |
1216 | ||
18a16cc5 NC |
1217 | (Although I should note that we're not certain that doing this for the general |
1218 | case is worth it) | |
1219 | ||
52960e22 JC |
1220 | =head2 optimize tail-calls |
1221 | ||
1222 | Tail-calls present an opportunity for broadly applicable optimization; | |
1223 | anywhere that C<< return foo(...) >> is called, the outer return can | |
1224 | be replaced by a goto, and foo will return directly to the outer | |
1225 | caller, saving (conservatively) 25% of perl's call&return cost, which | |
1226 | is relatively higher than in C. The scheme language is known to do | |
1227 | this heavily. B::Concise provides good insight into where this | |
1228 | optimization is possible, ie anywhere entersub,leavesub op-sequence | |
1229 | occurs. | |
1230 | ||
1231 | perl -MO=Concise,-exec,a,b,-main -e 'sub a{ 1 }; sub b {a()}; b(2)' | |
1232 | ||
1233 | Bottom line on this is probably a new pp_tailcall function which | |
1234 | combines the code in pp_entersub, pp_leavesub. This should probably | |
1235 | be done 1st in XS, and using B::Generate to patch the new OP into the | |
1236 | optrees. | |
1237 | ||
0c397127 KW |
1238 | =head2 Add C<00dddd> |
1239 | ||
1240 | It has been proposed that octal constants be specifiable through the syntax | |
1241 | C<0oddddd>, parallel to the existing construct to specify hex constants | |
1242 | C<0xddddd> | |
1243 | ||
0bdfc961 NC |
1244 | =head1 Big projects |
1245 | ||
1246 | Tasks that will get your name mentioned in the description of the "Highlights | |
fd2dadea | 1247 | of 5.14" |
0bdfc961 NC |
1248 | |
1249 | =head2 make ithreads more robust | |
1250 | ||
4e577f8b | 1251 | Generally make ithreads more robust. See also L</iCOW> |
0bdfc961 NC |
1252 | |
1253 | This task is incremental - even a little bit of work on it will help, and | |
1254 | will be greatly appreciated. | |
1255 | ||
07577ec1 FC |
1256 | One bit would be to determine how to clone directory handles on systems |
1257 | without a C<fchdir> function (in sv.c:Perl_dirp_dup). | |
6c047da7 | 1258 | |
59c7f7d5 RGS |
1259 | Fix Perl_sv_dup, et al so that threads can return objects. |
1260 | ||
0bdfc961 NC |
1261 | =head2 iCOW |
1262 | ||
1263 | Sarathy and Arthur have a proposal for an improved Copy On Write which | |
1264 | specifically will be able to COW new ithreads. If this can be implemented | |
1265 | it would be a good thing. | |
1266 | ||
1267 | =head2 (?{...}) closures in regexps | |
1268 | ||
1269 | Fix (or rewrite) the implementation of the C</(?{...})/> closures. | |
1270 | ||
6bda09f9 YO |
1271 | =head2 Add class set operations to regexp engine |
1272 | ||
1273 | Apparently these are quite useful. Anyway, Jeffery Friedl wants them. | |
1274 | ||
1275 | demerphq has this on his todo list, but right at the bottom. | |
44a7a252 JV |
1276 | |
1277 | ||
1278 | =head1 Tasks for microperl | |
1279 | ||
1280 | ||
1281 | [ Each and every one of these may be obsolete, but they were listed | |
1282 | in the old Todo.micro file] | |
1283 | ||
1284 | ||
1285 | =head2 make creating uconfig.sh automatic | |
1286 | ||
1287 | =head2 make creating Makefile.micro automatic | |
1288 | ||
1289 | =head2 do away with fork/exec/wait? | |
1290 | ||
1291 | (system, popen should be enough?) | |
1292 | ||
1293 | =head2 some of the uconfig.sh really needs to be probed (using cc) in buildtime: | |
1294 | ||
1295 | (uConfigure? :-) native datatype widths and endianness come to mind | |
1296 |