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1 | =head1 NAME |
2 | |
3 | perltodo - Perl TO-DO List |
4 | |
5 | =head1 DESCRIPTION |
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6 | |
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7 | This is a list of wishes for Perl. The tasks we think are smaller or |
8 | easier are listed first. Anyone is welcome to work on any of these, |
9 | but it's a good idea to first contact I<perl5-porters@perl.org> to |
10 | avoid duplication of effort, and to learn from any previous attempts. |
11 | By all means contact a pumpking privately first if you prefer. |
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12 | |
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13 | Whilst patches to make the list shorter are most welcome, ideas to add to |
14 | the list are also encouraged. Check the perl5-porters archives for past |
15 | ideas, and any discussion about them. One set of archives may be found at: |
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16 | |
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17 | http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/ |
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18 | |
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19 | What can we offer you in return? Fame, fortune, and everlasting glory? Maybe |
20 | not, but if your patch is incorporated, then we'll add your name to the |
21 | F<AUTHORS> file, which ships in the official distribution. How many other |
22 | programming languages offer you 1 line of immortality? |
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23 | |
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24 | =head1 Tasks that only need Perl knowledge |
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25 | |
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26 | =head2 Remove duplication of test setup. |
27 | |
28 | Schwern notes, that there's duplication of code - lots and lots of tests have |
29 | some variation on the big block of C<$Is_Foo> checks. We can safely put this |
30 | into a file, change it to build an C<%Is> hash and require it. Maybe just put |
31 | it into F<test.pl>. Throw in the handy tainting subroutines. |
32 | |
412f19a0 |
33 | =head2 merge common code in installperl and installman |
34 | |
35 | There are some common subroutines and a common C<BEGIN> block in F<installperl> |
36 | and F<installman>. These should probably be merged. It would also be good to |
37 | check for duplication in all the utility scripts supplied in the source |
38 | tarball. It might be good to move them all to a subdirectory, but this would |
39 | require careful checking to find all places that call them, and change those |
40 | correctly. |
41 | |
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42 | =head2 common test code for timed bail out |
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43 | |
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44 | Write portable self destruct code for tests to stop them burning CPU in |
45 | infinite loops. This needs to avoid using alarm, as some of the tests are |
46 | testing alarm/sleep or timers. |
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47 | |
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48 | =head2 POD -E<gt> HTML conversion in the core still sucks |
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49 | |
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50 | Which is crazy given just how simple POD purports to be, and how simple HTML |
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51 | can be. It's not actually I<as> simple as it sounds, particularly with the |
52 | flexibility POD allows for C<=item>, but it would be good to improve the |
53 | visual appeal of the HTML generated, and to avoid it having any validation |
54 | errors. See also L</make HTML install work>, as the layout of installation tree |
55 | is needed to improve the cross-linking. |
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56 | |
dc0fb092 |
57 | The addition of C<Pod::Simple> and its related modules may make this task |
58 | easier to complete. |
59 | |
8537f021 |
60 | =head2 merge checkpods and podchecker |
61 | |
62 | F<pod/checkpods.PL> (and C<make check> in the F<pod/> subdirectory) |
63 | implements a very basic check for pod files, but the errors it discovers |
64 | aren't found by podchecker. Add this check to podchecker, get rid of |
65 | checkpods and have C<make check> use podchecker. |
66 | |
aa237293 |
67 | =head2 Parallel testing |
68 | |
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69 | (This probably impacts much more than the core: also the Test::Harness |
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70 | and TAP::* modules on CPAN.) |
71 | |
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72 | The core regression test suite is getting ever more comprehensive, which has |
73 | the side effect that it takes longer to run. This isn't so good. Investigate |
74 | whether it would be feasible to give the harness script the B<option> of |
75 | running sets of tests in parallel. This would be useful for tests in |
76 | F<t/op/*.t> and F<t/uni/*.t> and maybe some sets of tests in F<lib/>. |
77 | |
78 | Questions to answer |
79 | |
80 | =over 4 |
81 | |
82 | =item 1 |
83 | |
84 | How does screen layout work when you're running more than one test? |
85 | |
86 | =item 2 |
87 | |
88 | How does the caller of test specify how many tests to run in parallel? |
89 | |
90 | =item 3 |
91 | |
92 | How do setup/teardown tests identify themselves? |
93 | |
94 | =back |
95 | |
96 | Pugs already does parallel testing - can their approach be re-used? |
97 | |
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98 | =head2 Make Schwern poorer |
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99 | |
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100 | We should have tests for everything. When all the core's modules are tested, |
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101 | Schwern has promised to donate to $500 to TPF. We may need volunteers to |
102 | hold him upside down and shake vigorously in order to actually extract the |
103 | cash. |
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104 | |
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105 | =head2 Improve the coverage of the core tests |
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106 | |
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107 | Use Devel::Cover to ascertain the core modules's test coverage, then add |
108 | tests that are currently missing. |
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109 | |
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110 | =head2 test B |
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111 | |
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112 | A full test suite for the B module would be nice. |
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113 | |
636e63cb |
114 | =head2 Deparse inlined constants |
115 | |
116 | Code such as this |
117 | |
118 | use constant PI => 4; |
119 | warn PI |
120 | |
121 | will currently deparse as |
122 | |
123 | use constant ('PI', 4); |
124 | warn 4; |
125 | |
126 | because the tokenizer inlines the value of the constant subroutine C<PI>. |
127 | This allows various compile time optimisations, such as constant folding |
128 | and dead code elimination. Where these haven't happened (such as the example |
129 | above) it ought be possible to make B::Deparse work out the name of the |
130 | original constant, because just enough information survives in the symbol |
131 | table to do this. Specifically, the same scalar is used for the constant in |
132 | the optree as is used for the constant subroutine, so by iterating over all |
133 | symbol tables and generating a mapping of SV address to constant name, it |
134 | would be possible to provide B::Deparse with this functionality. |
135 | |
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136 | =head2 A decent benchmark |
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137 | |
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138 | C<perlbench> seems impervious to any recent changes made to the perl core. It |
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139 | would be useful to have a reasonable general benchmarking suite that roughly |
140 | represented what current perl programs do, and measurably reported whether |
141 | tweaks to the core improve, degrade or don't really affect performance, to |
142 | guide people attempting to optimise the guts of perl. Gisle would welcome |
143 | new tests for perlbench. |
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144 | |
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145 | =head2 fix tainting bugs |
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146 | |
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147 | Fix the bugs revealed by running the test suite with the C<-t> switch (via |
148 | C<make test.taintwarn>). |
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149 | |
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150 | =head2 Dual life everything |
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151 | |
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152 | As part of the "dists" plan, anything that doesn't belong in the smallest perl |
153 | distribution needs to be dual lifed. Anything else can be too. Figure out what |
154 | changes would be needed to package that module and its tests up for CPAN, and |
155 | do so. Test it with older perl releases, and fix the problems you find. |
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156 | |
a393eb28 |
157 | To make a minimal perl distribution, it's useful to look at |
158 | F<t/lib/commonsense.t>. |
159 | |
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160 | =head2 Improving C<threads::shared> |
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161 | |
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162 | Investigate whether C<threads::shared> could share aggregates properly with |
163 | only Perl level changes to shared.pm |
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164 | |
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165 | =head2 POSIX memory footprint |
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166 | |
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167 | Ilya observed that use POSIX; eats memory like there's no tomorrow, and at |
168 | various times worked to cut it down. There is probably still fat to cut out - |
169 | for example POSIX passes Exporter some very memory hungry data structures. |
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170 | |
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171 | =head2 embed.pl/makedef.pl |
172 | |
173 | There is a script F<embed.pl> that generates several header files to prefix |
174 | all of Perl's symbols in a consistent way, to provide some semblance of |
175 | namespace support in C<C>. Functions are declared in F<embed.fnc>, variables |
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176 | in F<interpvar.h>. Quite a few of the functions and variables |
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177 | are conditionally declared there, using C<#ifdef>. However, F<embed.pl> |
178 | doesn't understand the C macros, so the rules about which symbols are present |
179 | when is duplicated in F<makedef.pl>. Writing things twice is bad, m'kay. |
180 | It would be good to teach C<embed.pl> to understand the conditional |
181 | compilation, and hence remove the duplication, and the mistakes it has caused. |
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182 | |
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183 | =head2 use strict; and AutoLoad |
184 | |
185 | Currently if you write |
186 | |
187 | package Whack; |
188 | use AutoLoader 'AUTOLOAD'; |
189 | use strict; |
190 | 1; |
191 | __END__ |
192 | sub bloop { |
193 | print join (' ', No, strict, here), "!\n"; |
194 | } |
195 | |
196 | then C<use strict;> isn't in force within the autoloaded subroutines. It would |
197 | be more consistent (and less surprising) to arrange for all lexical pragmas |
198 | in force at the __END__ block to be in force within each autoloaded subroutine. |
199 | |
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200 | There's a similar problem with SelfLoader. |
201 | |
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202 | =head1 Tasks that need a little sysadmin-type knowledge |
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203 | |
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204 | Or if you prefer, tasks that you would learn from, and broaden your skills |
205 | base... |
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206 | |
cd793d32 |
207 | =head2 make HTML install work |
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208 | |
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209 | There is an C<installhtml> target in the Makefile. It's marked as |
210 | "experimental". It would be good to get this tested, make it work reliably, and |
211 | remove the "experimental" tag. This would include |
212 | |
213 | =over 4 |
214 | |
215 | =item 1 |
216 | |
217 | Checking that cross linking between various parts of the documentation works. |
218 | In particular that links work between the modules (files with POD in F<lib/>) |
219 | and the core documentation (files in F<pod/>) |
220 | |
221 | =item 2 |
222 | |
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223 | Work out how to split C<perlfunc> into chunks, preferably one per function |
224 | group, preferably with general case code that could be used elsewhere. |
225 | Challenges here are correctly identifying the groups of functions that go |
226 | together, and making the right named external cross-links point to the right |
227 | page. Things to be aware of are C<-X>, groups such as C<getpwnam> to |
228 | C<endservent>, two or more C<=items> giving the different parameter lists, such |
229 | as |
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230 | |
231 | =item substr EXPR,OFFSET,LENGTH,REPLACEMENT |
adebf063 |
232 | =item substr EXPR,OFFSET,LENGTH |
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233 | =item substr EXPR,OFFSET |
234 | |
235 | and different parameter lists having different meanings. (eg C<select>) |
236 | |
237 | =back |
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238 | |
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239 | =head2 compressed man pages |
240 | |
241 | Be able to install them. This would probably need a configure test to see how |
242 | the system does compressed man pages (same directory/different directory? |
243 | same filename/different filename), as well as tweaking the F<installman> script |
244 | to compress as necessary. |
245 | |
30222c0f |
246 | =head2 Add a code coverage target to the Makefile |
247 | |
248 | Make it easy for anyone to run Devel::Cover on the core's tests. The steps |
249 | to do this manually are roughly |
250 | |
251 | =over 4 |
252 | |
253 | =item * |
254 | |
255 | do a normal C<Configure>, but include Devel::Cover as a module to install |
256 | (see F<INSTALL> for how to do this) |
257 | |
258 | =item * |
259 | |
260 | make perl |
261 | |
262 | =item * |
263 | |
264 | cd t; HARNESS_PERL_SWITCHES=-MDevel::Cover ./perl -I../lib harness |
265 | |
266 | =item * |
267 | |
268 | Process the resulting Devel::Cover database |
269 | |
270 | =back |
271 | |
272 | This just give you the coverage of the F<.pm>s. To also get the C level |
273 | coverage you need to |
274 | |
275 | =over 4 |
276 | |
277 | =item * |
278 | |
279 | Additionally tell C<Configure> to use the appropriate C compiler flags for |
280 | C<gcov> |
281 | |
282 | =item * |
283 | |
284 | make perl.gcov |
285 | |
286 | (instead of C<make perl>) |
287 | |
288 | =item * |
289 | |
290 | After running the tests run C<gcov> to generate all the F<.gcov> files. |
291 | (Including down in the subdirectories of F<ext/> |
292 | |
293 | =item * |
294 | |
295 | (From the top level perl directory) run C<gcov2perl> on all the C<.gcov> files |
296 | to get their stats into the cover_db directory. |
297 | |
298 | =item * |
299 | |
300 | Then process the Devel::Cover database |
301 | |
302 | =back |
303 | |
304 | It would be good to add a single switch to C<Configure> to specify that you |
305 | wanted to perform perl level coverage, and another to specify C level |
306 | coverage, and have C<Configure> and the F<Makefile> do all the right things |
307 | automatically. |
308 | |
02f21748 |
309 | =head2 Make Config.pm cope with differences between built and installed perl |
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310 | |
311 | Quite often vendors ship a perl binary compiled with their (pay-for) |
312 | compilers. People install a free compiler, such as gcc. To work out how to |
313 | build extensions, Perl interrogates C<%Config>, so in this situation |
314 | C<%Config> describes compilers that aren't there, and extension building |
315 | fails. This forces people into choosing between re-compiling perl themselves |
316 | using the compiler they have, or only using modules that the vendor ships. |
317 | |
318 | It would be good to find a way teach C<Config.pm> about the installation setup, |
319 | possibly involving probing at install time or later, so that the C<%Config> in |
320 | a binary distribution better describes the installed machine, when the |
321 | installed machine differs from the build machine in some significant way. |
322 | |
728f4ecd |
323 | =head2 linker specification files |
324 | |
325 | Some platforms mandate that you provide a list of a shared library's external |
326 | symbols to the linker, so the core already has the infrastructure in place to |
327 | do this for generating shared perl libraries. My understanding is that the |
328 | GNU toolchain can accept an optional linker specification file, and restrict |
329 | visibility just to symbols declared in that file. It would be good to extend |
330 | F<makedef.pl> to support this format, and to provide a means within |
331 | C<Configure> to enable it. This would allow Unix users to test that the |
332 | export list is correct, and to build a perl that does not pollute the global |
333 | namespace with private symbols. |
334 | |
a229ae3b |
335 | =head2 Cross-compile support |
336 | |
337 | Currently C<Configure> understands C<-Dusecrosscompile> option. This option |
338 | arranges for building C<miniperl> for TARGET machine, so this C<miniperl> is |
339 | assumed then to be copied to TARGET machine and used as a replacement of full |
340 | C<perl> executable. |
341 | |
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342 | This could be done little differently. Namely C<miniperl> should be built for |
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343 | HOST and then full C<perl> with extensions should be compiled for TARGET. |
d1307786 |
344 | This, however, might require extra trickery for %Config: we have one config |
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345 | first for HOST and then another for TARGET. Tools like MakeMaker will be |
346 | mightily confused. Having around two different types of executables and |
347 | libraries (HOST and TARGET) makes life interesting for Makefiles and |
348 | shell (and Perl) scripts. There is $Config{run}, normally empty, which |
349 | can be used as an execution wrapper. Also note that in some |
350 | cross-compilation/execution environments the HOST and the TARGET do |
351 | not see the same filesystem(s), the $Config{run} may need to do some |
352 | file/directory copying back and forth. |
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353 | |
8537f021 |
354 | =head2 roffitall |
355 | |
356 | Make F<pod/roffitall> be updated by F<pod/buildtoc>. |
357 | |
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358 | =head1 Tasks that need a little C knowledge |
359 | |
360 | These tasks would need a little C knowledge, but don't need any specific |
361 | background or experience with XS, or how the Perl interpreter works |
362 | |
3d826b29 |
363 | =head2 Weed out needless PERL_UNUSED_ARG |
364 | |
365 | The C code uses the macro C<PERL_UNUSED_ARG> to stop compilers warning about |
366 | unused arguments. Often the arguments can't be removed, as there is an |
367 | external constraint that determines the prototype of the function, so this |
368 | approach is valid. However, there are some cases where C<PERL_UNUSED_ARG> |
369 | could be removed. Specifically |
370 | |
371 | =over 4 |
372 | |
373 | =item * |
374 | |
375 | The prototypes of (nearly all) static functions can be changed |
376 | |
377 | =item * |
378 | |
379 | Unused arguments generated by short cut macros are wasteful - the short cut |
380 | macro used can be changed. |
381 | |
382 | =back |
383 | |
fbf638cb |
384 | =head2 Modernize the order of directories in @INC |
385 | |
386 | The way @INC is laid out by default, one cannot upgrade core (dual-life) |
387 | modules without overwriting files. This causes problems for binary |
3d14fd97 |
388 | package builders. One possible proposal is laid out in this |
389 | message: |
390 | L<http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/2002-04/msg02380.html>. |
fbf638cb |
391 | |
bcbaa2d5 |
392 | =head2 -Duse32bit* |
393 | |
394 | Natively 64-bit systems need neither -Duse64bitint nor -Duse64bitall. |
395 | On these systems, it might be the default compilation mode, and there |
396 | is currently no guarantee that passing no use64bitall option to the |
397 | Configure process will build a 32bit perl. Implementing -Duse32bit* |
398 | options would be nice for perl 5.12. |
399 | |
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400 | =head2 Make it clear from -v if this is the exact official release |
89007cb3 |
401 | |
617eabfa |
402 | Currently perl from C<p4>/C<rsync> ships with a F<patchlevel.h> file that |
403 | usually defines one local patch, of the form "MAINT12345" or "RC1". The output |
404 | of perl -v doesn't report that a perl isn't an official release, and this |
89007cb3 |
405 | information can get lost in bugs reports. Because of this, the minor version |
fa11829f |
406 | isn't bumped up until RC time, to minimise the possibility of versions of perl |
89007cb3 |
407 | escaping that believe themselves to be newer than they actually are. |
408 | |
409 | It would be useful to find an elegant way to have the "this is an interim |
410 | maintenance release" or "this is a release candidate" in the terse -v output, |
411 | and have it so that it's easy for the pumpking to remove this just as the |
412 | release tarball is rolled up. This way the version pulled out of rsync would |
413 | always say "I'm a development release" and it would be safe to bump the |
414 | reported minor version as soon as a release ships, which would aid perl |
415 | developers. |
416 | |
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417 | This task is really about thinking of an elegant way to arrange the C source |
418 | such that it's trivial for the Pumpking to flag "this is an official release" |
419 | when making a tarball, yet leave the default source saying "I'm not the |
420 | official release". |
421 | |
fee0a0f7 |
422 | =head2 Profile Perl - am I hot or not? |
62403a3c |
423 | |
fee0a0f7 |
424 | The Perl source code is stable enough that it makes sense to profile it, |
425 | identify and optimise the hotspots. It would be good to measure the |
426 | performance of the Perl interpreter using free tools such as cachegrind, |
427 | gprof, and dtrace, and work to reduce the bottlenecks they reveal. |
428 | |
429 | As part of this, the idea of F<pp_hot.c> is that it contains the I<hot> ops, |
430 | the ops that are most commonly used. The idea is that by grouping them, their |
431 | object code will be adjacent in the executable, so they have a greater chance |
432 | of already being in the CPU cache (or swapped in) due to being near another op |
433 | already in use. |
62403a3c |
434 | |
435 | Except that it's not clear if these really are the most commonly used ops. So |
fee0a0f7 |
436 | as part of exercising your skills with coverage and profiling tools you might |
437 | want to determine what ops I<really> are the most commonly used. And in turn |
438 | suggest evictions and promotions to achieve a better F<pp_hot.c>. |
62403a3c |
439 | |
98fed0ad |
440 | =head2 Allocate OPs from arenas |
441 | |
442 | Currently all new OP structures are individually malloc()ed and free()d. |
443 | All C<malloc> implementations have space overheads, and are now as fast as |
444 | custom allocates so it would both use less memory and less CPU to allocate |
445 | the various OP structures from arenas. The SV arena code can probably be |
446 | re-used for this. |
447 | |
539f2c54 |
448 | Note that Configuring perl with C<-Accflags=-DPL_OP_SLAB_ALLOC> will use |
449 | Perl_Slab_alloc() to pack optrees into a contiguous block, which is |
450 | probably superior to the use of OP arenas, esp. from a cache locality |
451 | standpoint. See L<Profile Perl - am I hot or not?>. |
452 | |
a229ae3b |
453 | =head2 Improve win32/wince.c |
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454 | |
a229ae3b |
455 | Currently, numerous functions look virtually, if not completely, |
02f21748 |
456 | identical in both C<win32/wince.c> and C<win32/win32.c> files, which can't |
6d71adcd |
457 | be good. |
458 | |
c5b31784 |
459 | =head2 Use secure CRT functions when building with VC8 on Win32 |
460 | |
461 | Visual C++ 2005 (VC++ 8.x) deprecated a number of CRT functions on the basis |
462 | that they were "unsafe" and introduced differently named secure versions of |
463 | them as replacements, e.g. instead of writing |
464 | |
465 | FILE* f = fopen(__FILE__, "r"); |
466 | |
467 | one should now write |
468 | |
469 | FILE* f; |
470 | errno_t err = fopen_s(&f, __FILE__, "r"); |
471 | |
472 | Currently, the warnings about these deprecations have been disabled by adding |
473 | -D_CRT_SECURE_NO_DEPRECATE to the CFLAGS. It would be nice to remove that |
474 | warning suppressant and actually make use of the new secure CRT functions. |
475 | |
476 | There is also a similar issue with POSIX CRT function names like fileno having |
477 | been deprecated in favour of ISO C++ conformant names like _fileno. These |
26a6faa8 |
478 | warnings are also currently suppressed by adding -D_CRT_NONSTDC_NO_DEPRECATE. It |
c5b31784 |
479 | might be nice to do as Microsoft suggest here too, although, unlike the secure |
480 | functions issue, there is presumably little or no benefit in this case. |
481 | |
038ae9a4 |
482 | =head2 Fix POSIX::access() and chdir() on Win32 |
483 | |
484 | These functions currently take no account of DACLs and therefore do not behave |
485 | correctly in situations where access is restricted by DACLs (as opposed to the |
486 | read-only attribute). |
487 | |
488 | Furthermore, POSIX::access() behaves differently for directories having the |
489 | read-only attribute set depending on what CRT library is being used. For |
490 | example, the _access() function in the VC6 and VC7 CRTs (wrongly) claim that |
491 | such directories are not writable, whereas in fact all directories are writable |
492 | unless access is denied by DACLs. (In the case of directories, the read-only |
493 | attribute actually only means that the directory cannot be deleted.) This CRT |
494 | bug is fixed in the VC8 and VC9 CRTs (but, of course, the directory may still |
495 | not actually be writable if access is indeed denied by DACLs). |
496 | |
497 | For the chdir() issue, see ActiveState bug #74552: |
498 | http://bugs.activestate.com/show_bug.cgi?id=74552 |
499 | |
500 | Therefore, DACLs should be checked both for consistency across CRTs and for |
501 | the correct answer. |
502 | |
503 | (Note that perl's -w operator should not be modified to check DACLs. It has |
504 | been written so that it reflects the state of the read-only attribute, even |
505 | for directories (whatever CRT is being used), for symmetry with chmod().) |
506 | |
16815324 |
507 | =head2 strcat(), strcpy(), strncat(), strncpy(), sprintf(), vsprintf() |
508 | |
509 | Maybe create a utility that checks after each libperl.a creation that |
510 | none of the above (nor sprintf(), vsprintf(), or *SHUDDER* gets()) |
511 | ever creep back to libperl.a. |
512 | |
513 | nm libperl.a | ./miniperl -alne '$o = $F[0] if /:$/; print "$o $F[1]" if $F[0] eq "U" && $F[1] =~ /^(?:strn?c(?:at|py)|v?sprintf|gets)$/' |
514 | |
515 | Note, of course, that this will only tell whether B<your> platform |
516 | is using those naughty interfaces. |
517 | |
de96509d |
518 | =head2 -D_FORTIFY_SOURCE=2, -fstack-protector |
519 | |
520 | Recent glibcs support C<-D_FORTIFY_SOURCE=2> and recent gcc |
521 | (4.1 onwards?) supports C<-fstack-protector>, both of which give |
522 | protection against various kinds of buffer overflow problems. |
523 | These should probably be used for compiling Perl whenever available, |
524 | Configure and/or hints files should be adjusted to probe for the |
525 | availability of these features and enable them as appropriate. |
16815324 |
526 | |
8964cfe0 |
527 | =head2 Arenas for GPs? For MAGIC? |
528 | |
529 | C<struct gp> and C<struct magic> are both currently allocated by C<malloc>. |
530 | It might be a speed or memory saving to change to using arenas. Or it might |
531 | not. It would need some suitable benchmarking first. In particular, C<GP>s |
532 | can probably be changed with minimal compatibility impact (probably nothing |
533 | outside of the core, or even outside of F<gv.c> allocates them), but they |
534 | probably aren't allocated/deallocated often enough for a speed saving. Whereas |
535 | C<MAGIC> is allocated/deallocated more often, but in turn, is also something |
536 | more externally visible, so changing the rules here may bite external code. |
537 | |
538 | |
6d71adcd |
539 | =head1 Tasks that need a knowledge of XS |
540 | |
541 | These tasks would need C knowledge, and roughly the level of knowledge of |
542 | the perl API that comes from writing modules that use XS to interface to |
543 | C. |
544 | |
6d71adcd |
545 | =head2 autovivification |
546 | |
547 | Make all autovivification consistent w.r.t LVALUE/RVALUE and strict/no strict; |
548 | |
549 | This task is incremental - even a little bit of work on it will help. |
550 | |
551 | =head2 Unicode in Filenames |
552 | |
553 | chdir, chmod, chown, chroot, exec, glob, link, lstat, mkdir, open, |
554 | opendir, qx, readdir, readlink, rename, rmdir, stat, symlink, sysopen, |
555 | system, truncate, unlink, utime, -X. All these could potentially accept |
556 | Unicode filenames either as input or output (and in the case of system |
557 | and qx Unicode in general, as input or output to/from the shell). |
558 | Whether a filesystem - an operating system pair understands Unicode in |
559 | filenames varies. |
560 | |
561 | Known combinations that have some level of understanding include |
562 | Microsoft NTFS, Apple HFS+ (In Mac OS 9 and X) and Apple UFS (in Mac |
563 | OS X), NFS v4 is rumored to be Unicode, and of course Plan 9. How to |
564 | create Unicode filenames, what forms of Unicode are accepted and used |
565 | (UCS-2, UTF-16, UTF-8), what (if any) is the normalization form used, |
566 | and so on, varies. Finding the right level of interfacing to Perl |
567 | requires some thought. Remember that an OS does not implicate a |
568 | filesystem. |
569 | |
570 | (The Windows -C command flag "wide API support" has been at least |
571 | temporarily retired in 5.8.1, and the -C has been repurposed, see |
572 | L<perlrun>.) |
573 | |
87a942b1 |
574 | Most probably the right way to do this would be this: |
575 | L</"Virtualize operating system access">. |
576 | |
6d71adcd |
577 | =head2 Unicode in %ENV |
578 | |
579 | Currently the %ENV entries are always byte strings. |
87a942b1 |
580 | See L</"Virtualize operating system access">. |
6d71adcd |
581 | |
1f2e7916 |
582 | =head2 Unicode and glob() |
583 | |
584 | Currently glob patterns and filenames returned from File::Glob::glob() |
87a942b1 |
585 | are always byte strings. See L</"Virtualize operating system access">. |
1f2e7916 |
586 | |
dbb0c492 |
587 | =head2 Unicode and lc/uc operators |
588 | |
589 | Some built-in operators (C<lc>, C<uc>, etc.) behave differently, based on |
590 | what the internal encoding of their argument is. That should not be the |
591 | case. Maybe add a pragma to switch behaviour. |
592 | |
6d71adcd |
593 | =head2 use less 'memory' |
594 | |
595 | Investigate trade offs to switch out perl's choices on memory usage. |
596 | Particularly perl should be able to give memory back. |
597 | |
598 | This task is incremental - even a little bit of work on it will help. |
599 | |
600 | =head2 Re-implement C<:unique> in a way that is actually thread-safe |
601 | |
602 | The old implementation made bad assumptions on several levels. A good 90% |
603 | solution might be just to make C<:unique> work to share the string buffer |
604 | of SvPVs. That way large constant strings can be shared between ithreads, |
605 | such as the configuration information in F<Config>. |
606 | |
607 | =head2 Make tainting consistent |
608 | |
609 | Tainting would be easier to use if it didn't take documented shortcuts and |
610 | allow taint to "leak" everywhere within an expression. |
611 | |
612 | =head2 readpipe(LIST) |
613 | |
614 | system() accepts a LIST syntax (and a PROGRAM LIST syntax) to avoid |
615 | running a shell. readpipe() (the function behind qx//) could be similarly |
616 | extended. |
617 | |
6d71adcd |
618 | =head2 Audit the code for destruction ordering assumptions |
619 | |
620 | Change 25773 notes |
621 | |
622 | /* Need to check SvMAGICAL, as during global destruction it may be that |
623 | AvARYLEN(av) has been freed before av, and hence the SvANY() pointer |
624 | is now part of the linked list of SV heads, rather than pointing to |
625 | the original body. */ |
626 | /* FIXME - audit the code for other bugs like this one. */ |
627 | |
628 | adding the C<SvMAGICAL> check to |
629 | |
630 | if (AvARYLEN(av) && SvMAGICAL(AvARYLEN(av))) { |
631 | MAGIC *mg = mg_find (AvARYLEN(av), PERL_MAGIC_arylen); |
632 | |
633 | Go through the core and look for similar assumptions that SVs have particular |
634 | types, as all bets are off during global destruction. |
635 | |
749904bf |
636 | =head2 Extend PerlIO and PerlIO::Scalar |
637 | |
638 | PerlIO::Scalar doesn't know how to truncate(). Implementing this |
639 | would require extending the PerlIO vtable. |
640 | |
641 | Similarly the PerlIO vtable doesn't know about formats (write()), or |
642 | about stat(), or chmod()/chown(), utime(), or flock(). |
643 | |
644 | (For PerlIO::Scalar it's hard to see what e.g. mode bits or ownership |
645 | would mean.) |
646 | |
647 | PerlIO doesn't do directories or symlinks, either: mkdir(), rmdir(), |
648 | opendir(), closedir(), seekdir(), rewinddir(), glob(); symlink(), |
649 | readlink(). |
650 | |
94da6c29 |
651 | See also L</"Virtualize operating system access">. |
652 | |
3236f110 |
653 | =head2 -C on the #! line |
654 | |
655 | It should be possible to make -C work correctly if found on the #! line, |
656 | given that all perl command line options are strict ASCII, and -C changes |
657 | only the interpretation of non-ASCII characters, and not for the script file |
658 | handle. To make it work needs some investigation of the ordering of function |
659 | calls during startup, and (by implication) a bit of tweaking of that order. |
660 | |
d6c1e11f |
661 | =head2 Organize error messages |
662 | |
663 | Perl's diagnostics (error messages, see L<perldiag>) could use |
a8d0aeb9 |
664 | reorganizing and formalizing so that each error message has its |
d6c1e11f |
665 | stable-for-all-eternity unique id, categorized by severity, type, and |
666 | subsystem. (The error messages would be listed in a datafile outside |
c4bd451b |
667 | of the Perl source code, and the source code would only refer to the |
668 | messages by the id.) This clean-up and regularizing should apply |
d6c1e11f |
669 | for all croak() messages. |
670 | |
671 | This would enable all sorts of things: easier translation/localization |
672 | of the messages (though please do keep in mind the caveats of |
673 | L<Locale::Maketext> about too straightforward approaches to |
674 | translation), filtering by severity, and instead of grepping for a |
675 | particular error message one could look for a stable error id. (Of |
676 | course, changing the error messages by default would break all the |
677 | existing software depending on some particular error message...) |
678 | |
679 | This kind of functionality is known as I<message catalogs>. Look for |
680 | inspiration for example in the catgets() system, possibly even use it |
681 | if available-- but B<only> if available, all platforms will B<not> |
de96509d |
682 | have catgets(). |
d6c1e11f |
683 | |
684 | For the really pure at heart, consider extending this item to cover |
685 | also the warning messages (see L<perllexwarn>, C<warnings.pl>). |
3236f110 |
686 | |
0bdfc961 |
687 | =head1 Tasks that need a knowledge of the interpreter |
3298bd4d |
688 | |
0bdfc961 |
689 | These tasks would need C knowledge, and knowledge of how the interpreter works, |
690 | or a willingness to learn. |
3298bd4d |
691 | |
718140ec |
692 | =head2 lexicals used only once |
693 | |
694 | This warns: |
695 | |
696 | $ perl -we '$pie = 42' |
697 | Name "main::pie" used only once: possible typo at -e line 1. |
698 | |
699 | This does not: |
700 | |
701 | $ perl -we 'my $pie = 42' |
702 | |
703 | Logically all lexicals used only once should warn, if the user asks for |
d6f4ea2e |
704 | warnings. An unworked RT ticket (#5087) has been open for almost seven |
705 | years for this discrepancy. |
718140ec |
706 | |
a3d15f9a |
707 | =head2 UTF-8 revamp |
708 | |
709 | The handling of Unicode is unclean in many places. For example, the regexp |
710 | engine matches in Unicode semantics whenever the string or the pattern is |
711 | flagged as UTF-8, but that should not be dependent on an internal storage |
712 | detail of the string. Likewise, case folding behaviour is dependent on the |
713 | UTF8 internal flag being on or off. |
714 | |
715 | =head2 Properly Unicode safe tokeniser and pads. |
716 | |
717 | The tokeniser isn't actually very UTF-8 clean. C<use utf8;> is a hack - |
718 | variable names are stored in stashes as raw bytes, without the utf-8 flag |
719 | set. The pad API only takes a C<char *> pointer, so that's all bytes too. The |
720 | tokeniser ignores the UTF-8-ness of C<PL_rsfp>, or any SVs returned from |
721 | source filters. All this could be fixed. |
722 | |
636e63cb |
723 | =head2 state variable initialization in list context |
724 | |
725 | Currently this is illegal: |
726 | |
727 | state ($a, $b) = foo(); |
728 | |
a2874905 |
729 | In Perl 6, C<state ($a) = foo();> and C<(state $a) = foo();> have different |
a8d0aeb9 |
730 | semantics, which is tricky to implement in Perl 5 as currently they produce |
a2874905 |
731 | the same opcode trees. The Perl 6 design is firm, so it would be good to |
a8d0aeb9 |
732 | implement the necessary code in Perl 5. There are comments in |
a2874905 |
733 | C<Perl_newASSIGNOP()> that show the code paths taken by various assignment |
734 | constructions involving state variables. |
636e63cb |
735 | |
4fedb12c |
736 | =head2 Implement $value ~~ 0 .. $range |
737 | |
738 | It would be nice to extend the syntax of the C<~~> operator to also |
739 | understand numeric (and maybe alphanumeric) ranges. |
a393eb28 |
740 | |
741 | =head2 A does() built-in |
742 | |
743 | Like ref(), only useful. It would call the C<DOES> method on objects; it |
744 | would also tell whether something can be dereferenced as an |
745 | array/hash/etc., or used as a regexp, etc. |
746 | L<http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/2007-03/msg00481.html> |
747 | |
748 | =head2 Tied filehandles and write() don't mix |
749 | |
750 | There is no method on tied filehandles to allow them to be called back by |
751 | formats. |
4fedb12c |
752 | |
d10fc472 |
753 | =head2 Attach/detach debugger from running program |
1626a787 |
754 | |
cd793d32 |
755 | The old perltodo notes "With C<gdb>, you can attach the debugger to a running |
756 | program if you pass the process ID. It would be good to do this with the Perl |
0bdfc961 |
757 | debugger on a running Perl program, although I'm not sure how it would be |
758 | done." ssh and screen do this with named pipes in /tmp. Maybe we can too. |
1626a787 |
759 | |
a8cb5b9e |
760 | =head2 Optimize away empty destructors |
761 | |
762 | Defining an empty DESTROY method might be useful (notably in |
763 | AUTOLOAD-enabled classes), but it's still a bit expensive to call. That |
764 | could probably be optimized. |
765 | |
0bdfc961 |
766 | =head2 LVALUE functions for lists |
767 | |
768 | The old perltodo notes that lvalue functions don't work for list or hash |
769 | slices. This would be good to fix. |
770 | |
771 | =head2 LVALUE functions in the debugger |
772 | |
773 | The old perltodo notes that lvalue functions don't work in the debugger. This |
774 | would be good to fix. |
775 | |
0bdfc961 |
776 | =head2 regexp optimiser optional |
777 | |
778 | The regexp optimiser is not optional. It should configurable to be, to allow |
779 | its performance to be measured, and its bugs to be easily demonstrated. |
780 | |
02f21748 |
781 | =head2 delete &function |
782 | |
783 | Allow to delete functions. One can already undef them, but they're still |
784 | in the stash. |
785 | |
ef36c6a7 |
786 | =head2 C</w> regex modifier |
787 | |
788 | That flag would enable to match whole words, and also to interpolate |
789 | arrays as alternations. With it, C</P/w> would be roughly equivalent to: |
790 | |
791 | do { local $"='|'; /\b(?:P)\b/ } |
792 | |
793 | See L<http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/2007-01/msg00400.html> |
794 | for the discussion. |
795 | |
0bdfc961 |
796 | =head2 optional optimizer |
797 | |
798 | Make the peephole optimizer optional. Currently it performs two tasks as |
799 | it walks the optree - genuine peephole optimisations, and necessary fixups of |
800 | ops. It would be good to find an efficient way to switch out the |
801 | optimisations whilst keeping the fixups. |
802 | |
803 | =head2 You WANT *how* many |
804 | |
805 | Currently contexts are void, scalar and list. split has a special mechanism in |
806 | place to pass in the number of return values wanted. It would be useful to |
807 | have a general mechanism for this, backwards compatible and little speed hit. |
808 | This would allow proposals such as short circuiting sort to be implemented |
809 | as a module on CPAN. |
810 | |
811 | =head2 lexical aliases |
812 | |
813 | Allow lexical aliases (maybe via the syntax C<my \$alias = \$foo>. |
814 | |
815 | =head2 entersub XS vs Perl |
816 | |
817 | At the moment pp_entersub is huge, and has code to deal with entering both |
818 | perl and XS subroutines. Subroutine implementations rarely change between |
819 | perl and XS at run time, so investigate using 2 ops to enter subs (one for |
820 | XS, one for perl) and swap between if a sub is redefined. |
2810d901 |
821 | |
de535794 |
822 | =head2 Self-ties |
2810d901 |
823 | |
de535794 |
824 | Self-ties are currently illegal because they caused too many segfaults. Maybe |
a8d0aeb9 |
825 | the causes of these could be tracked down and self-ties on all types |
de535794 |
826 | reinstated. |
0bdfc961 |
827 | |
828 | =head2 Optimize away @_ |
829 | |
830 | The old perltodo notes "Look at the "reification" code in C<av.c>". |
831 | |
f092b1f4 |
832 | =head2 The yada yada yada operators |
833 | |
834 | Perl 6's Synopsis 3 says: |
835 | |
836 | I<The ... operator is the "yada, yada, yada" list operator, which is used as |
837 | the body in function prototypes. It complains bitterly (by calling fail) |
838 | if it is ever executed. Variant ??? calls warn, and !!! calls die.> |
839 | |
840 | Those would be nice to add to Perl 5. That could be done without new ops. |
841 | |
87a942b1 |
842 | =head2 Virtualize operating system access |
843 | |
844 | Implement a set of "vtables" that virtualizes operating system access |
845 | (open(), mkdir(), unlink(), readdir(), getenv(), etc.) At the very |
846 | least these interfaces should take SVs as "name" arguments instead of |
847 | bare char pointers; probably the most flexible and extensible way |
e1a3d5d1 |
848 | would be for the Perl-facing interfaces to accept HVs. The system |
849 | needs to be per-operating-system and per-file-system |
850 | hookable/filterable, preferably both from XS and Perl level |
87a942b1 |
851 | (L<perlport/"Files and Filesystems"> is good reading at this point, |
852 | in fact, all of L<perlport> is.) |
853 | |
e1a3d5d1 |
854 | This has actually already been implemented (but only for Win32), |
855 | take a look at F<iperlsys.h> and F<win32/perlhost.h>. While all Win32 |
856 | variants go through a set of "vtables" for operating system access, |
857 | non-Win32 systems currently go straight for the POSIX/UNIX-style |
858 | system/library call. Similar system as for Win32 should be |
859 | implemented for all platforms. The existing Win32 implementation |
860 | probably does not need to survive alongside this proposed new |
861 | implementation, the approaches could be merged. |
87a942b1 |
862 | |
863 | What would this give us? One often-asked-for feature this would |
94da6c29 |
864 | enable is using Unicode for filenames, and other "names" like %ENV, |
865 | usernames, hostnames, and so forth. |
866 | (See L<perlunicode/"When Unicode Does Not Happen">.) |
867 | |
868 | But this kind of virtualization would also allow for things like |
869 | virtual filesystems, virtual networks, and "sandboxes" (though as long |
870 | as dynamic loading of random object code is allowed, not very safe |
871 | sandboxes since external code of course know not of Perl's vtables). |
872 | An example of a smaller "sandbox" is that this feature can be used to |
873 | implement per-thread working directories: Win32 already does this. |
874 | |
875 | See also L</"Extend PerlIO and PerlIO::Scalar">. |
87a942b1 |
876 | |
ac6197af |
877 | =head2 Investigate PADTMP hash pessimisation |
878 | |
879 | The peephole optimier converts constants used for hash key lookups to shared |
057163d7 |
880 | hash key scalars. Under ithreads, something is undoing this work. |
ac6197af |
881 | See http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/2007-09/msg00793.html |
882 | |
057163d7 |
883 | =head2 Store the current pad in the OP slab allocator |
884 | |
885 | =for clarification |
886 | I hope that I got that "current pad" part correct |
887 | |
888 | Currently we leak ops in various cases of parse failure. I suggested that we |
889 | could solve this by always using the op slab allocator, and walking it to |
890 | free ops. Dave comments that as some ops are already freed during optree |
891 | creation one would have to mark which ops are freed, and not double free them |
892 | when walking the slab. He notes that one problem with this is that for some ops |
893 | you have to know which pad was current at the time of allocation, which does |
894 | change. I suggested storing a pointer to the current pad in the memory allocated |
895 | for the slab, and swapping to a new slab each time the pad changes. Dave thinks |
896 | that this would work. |
897 | |
52960e22 |
898 | =head2 repack the optree |
899 | |
900 | Repacking the optree after execution order is determined could allow |
057163d7 |
901 | removal of NULL ops, and optimal ordering of OPs with respect to cache-line |
902 | filling. The slab allocator could be reused for this purpose. I think that |
903 | the best way to do this is to make it an optional step just before the |
904 | completed optree is attached to anything else, and to use the slab allocator |
905 | unchanged, so that freeing ops is identical whether or not this step runs. |
906 | Note that the slab allocator allocates ops downwards in memory, so one would |
907 | have to actually "allocate" the ops in reverse-execution order to get them |
908 | contiguous in memory in execution order. |
909 | |
910 | See http://www.nntp.perl.org/group/perl.perl5.porters/2007/12/msg131975.html |
911 | |
912 | Note that running this copy, and then freeing all the old location ops would |
913 | cause their slabs to be freed, which would eliminate possible memory wastage if |
914 | the previous suggestion is implemented, and we swap slabs more frequently. |
52960e22 |
915 | |
12e06b6f |
916 | =head2 eliminate incorrect line numbers in warnings |
917 | |
918 | This code |
919 | |
920 | use warnings; |
921 | my $undef; |
922 | |
923 | if ($undef == 3) { |
924 | } elsif ($undef == 0) { |
925 | } |
926 | |
927 | produces this output |
928 | |
929 | Use of uninitialized value in numeric eq (==) at wrong.pl line 4. |
930 | Use of uninitialized value in numeric eq (==) at wrong.pl line 4. |
931 | |
932 | Clearly the line of the second warning is misreported - it should be line 5. |
933 | |
934 | The problem arises because there is no nextstate op between the execution of |
935 | the C<if> and the C<elsif>, hence C<PL_curcop> still reports that the currently |
936 | executing line is line 4. The solution might be to inject (somehow) more |
937 | nextstate ops, one for each C<elsif>. |
938 | |
939 | The problem is more general than C<elsif> (although the C<elsif> case is the |
940 | most common and the most confusing). Ideally this code |
941 | |
942 | use warnings; |
943 | my $undef; |
944 | |
945 | my $a = $undef + 1; |
946 | my $b |
947 | = $undef |
948 | + 1; |
949 | |
950 | would produce this output |
951 | |
952 | Use of uninitialized value $undef in addition (+) at wrong.pl line 4. |
953 | Use of uninitialized value $undef in addition (+) at wrong.pl line 7. |
954 | |
955 | (rather than lines 4 and 5), but this would seem to require every OP to carry |
956 | (at least) line number information. |
957 | |
958 | What might work is to have an optional line number in memory just before the |
959 | BASEOP structure, with a flag bit in the op to say whether it's present. |
960 | Initially during compile every OP would carry its line number. Then add a late |
961 | pass to the optimiser (potentially combined with L</repack the optree>) which |
962 | looks at the two ops on every edge of the graph of the execution path. If |
963 | the line number changes, flags the destination OP with this information. |
964 | Once all paths are traced, replace every op with the flag with a |
965 | nextstate-light op (that just updates C<PL_curcop>), which in turn then passes |
966 | control on to the true op. All ops would then be replaced by variants that |
967 | do not store the line number. (Which, logically, why it would work best in |
968 | conjunction with L</repack the optree>, as that is already copying/reallocating |
969 | all the OPs) |
970 | |
52960e22 |
971 | =head2 optimize tail-calls |
972 | |
973 | Tail-calls present an opportunity for broadly applicable optimization; |
974 | anywhere that C<< return foo(...) >> is called, the outer return can |
975 | be replaced by a goto, and foo will return directly to the outer |
976 | caller, saving (conservatively) 25% of perl's call&return cost, which |
977 | is relatively higher than in C. The scheme language is known to do |
978 | this heavily. B::Concise provides good insight into where this |
979 | optimization is possible, ie anywhere entersub,leavesub op-sequence |
980 | occurs. |
981 | |
982 | perl -MO=Concise,-exec,a,b,-main -e 'sub a{ 1 }; sub b {a()}; b(2)' |
983 | |
984 | Bottom line on this is probably a new pp_tailcall function which |
985 | combines the code in pp_entersub, pp_leavesub. This should probably |
986 | be done 1st in XS, and using B::Generate to patch the new OP into the |
987 | optrees. |
988 | |
0bdfc961 |
989 | =head1 Big projects |
990 | |
991 | Tasks that will get your name mentioned in the description of the "Highlights |
87a942b1 |
992 | of 5.12" |
0bdfc961 |
993 | |
994 | =head2 make ithreads more robust |
995 | |
4e577f8b |
996 | Generally make ithreads more robust. See also L</iCOW> |
0bdfc961 |
997 | |
998 | This task is incremental - even a little bit of work on it will help, and |
999 | will be greatly appreciated. |
1000 | |
6c047da7 |
1001 | One bit would be to write the missing code in sv.c:Perl_dirp_dup. |
1002 | |
59c7f7d5 |
1003 | Fix Perl_sv_dup, et al so that threads can return objects. |
1004 | |
0bdfc961 |
1005 | =head2 iCOW |
1006 | |
1007 | Sarathy and Arthur have a proposal for an improved Copy On Write which |
1008 | specifically will be able to COW new ithreads. If this can be implemented |
1009 | it would be a good thing. |
1010 | |
1011 | =head2 (?{...}) closures in regexps |
1012 | |
1013 | Fix (or rewrite) the implementation of the C</(?{...})/> closures. |
1014 | |
1015 | =head2 A re-entrant regexp engine |
1016 | |
1017 | This will allow the use of a regex from inside (?{ }), (??{ }) and |
1018 | (?(?{ })|) constructs. |
6bda09f9 |
1019 | |
6bda09f9 |
1020 | =head2 Add class set operations to regexp engine |
1021 | |
1022 | Apparently these are quite useful. Anyway, Jeffery Friedl wants them. |
1023 | |
1024 | demerphq has this on his todo list, but right at the bottom. |