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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 easier |
8 | are listed first. Anyone is welcome to work on any of these, but it's a good |
9 | idea to first contact I<perl5-porters@perl.org> to avoid duplication of |
10 | effort. By all means contact a pumpking privately first if you prefer. |
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11 | |
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12 | Whilst patches to make the list shorter are most welcome, ideas to add to |
13 | the list are also encouraged. Check the perl5-porters archives for past |
14 | ideas, and any discussion about them. One set of archives may be found at: |
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15 | |
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16 | http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/ |
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17 | |
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18 | |
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19 | |
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20 | |
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21 | |
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22 | =head1 Tasks that only need Perl knowledge |
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23 | |
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24 | =head2 common test code for timed bail out |
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25 | |
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26 | Write portable self destruct code for tests to stop them burning CPU in |
27 | infinite loops. This needs to avoid using alarm, as some of the tests are |
28 | testing alarm/sleep or timers. |
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29 | |
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30 | =head2 POD -> HTML conversion in the core still sucks |
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31 | |
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32 | Which is crazy given just how simple POD purports to be, and how simple HTML |
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33 | can be. It's not actually I<as> simple as it sounds, particularly with the |
34 | flexibility POD allows for C<=item>, but it would be good to improve the |
35 | visual appeal of the HTML generated, and to avoid it having any validation |
36 | errors. See also L</make HTML install work>, as the layout of installation tree |
37 | is needed to improve the cross-linking. |
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38 | |
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39 | =head2 Make Schwern poorer |
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40 | |
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41 | We should have for everything. When all the core's modules are tested, |
42 | Schwern has promised to donate to $500 to TPF. We may need volunteers to |
43 | hold him upside down and shake vigorously in order to actually extract the |
44 | cash. |
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45 | |
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46 | See F<t/lib/1_compile.t> for the 3 remaining modules that need tests. |
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47 | |
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48 | =head2 Improve the coverage of the core tests |
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49 | |
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50 | Use Devel::Cover to ascertain the core's test coverage, then add tests that |
51 | are currently missing. |
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52 | |
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53 | =head2 test B |
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54 | |
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55 | A full test suite for the B module would be nice. |
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56 | |
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57 | =head2 A decent benchmark |
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58 | |
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59 | perlbench seems impervious to any recent changes made to the perl core. It |
60 | would be useful to have a reasonable general benchmarking suite that roughly |
61 | represented what current perl programs do, and measurably reported whether |
62 | tweaks to the core improve, degrade or don't really affect performance, to |
63 | guide people attempting to optimise the guts of perl. Gisle would welcome |
64 | new tests for perlbench. |
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65 | |
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66 | =head2 fix tainting bugs |
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67 | |
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68 | Fix the bugs revealed by running the test suite with the C<-t> switch (via |
69 | C<make test.taintwarn>). |
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70 | |
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71 | =head2 Dual life everything |
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72 | |
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73 | As part of the "dists" plan, anything that doesn't belong in the smallest perl |
74 | distribution needs to be dual lifed. Anything else can be too. Figure out what |
75 | changes would be needed to package that module and its tests up for CPAN, and |
76 | do so. Test it with older perl releases, and fix the problems you find. |
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77 | |
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78 | =head2 Improving C<threads::shared> |
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79 | |
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80 | Investigate whether C<threads::shared> could share aggregates properly with |
81 | only Perl level changes to shared.pm |
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82 | |
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83 | =head2 POSIX memory footprint |
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84 | |
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85 | Ilya observed that use POSIX; eats memory like there's no tomorrow, and at |
86 | various times worked to cut it down. There is probably still fat to cut out - |
87 | for example POSIX passes Exporter some very memory hungry data structures. |
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88 | |
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89 | |
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90 | |
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91 | |
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92 | |
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93 | |
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94 | |
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95 | =head1 Tasks that need a little sysadmin-type knowledge |
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96 | |
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97 | Or if you prefer, tasks that you would learn from, and broaden your skills |
98 | base... |
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99 | |
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100 | =head2 make HTML install work |
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101 | |
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102 | There is an C<installhtml> target in the Makefile. It's marked as |
103 | "experimental". It would be good to get this tested, make it work reliably, and |
104 | remove the "experimental" tag. This would include |
105 | |
106 | =over 4 |
107 | |
108 | =item 1 |
109 | |
110 | Checking that cross linking between various parts of the documentation works. |
111 | In particular that links work between the modules (files with POD in F<lib/>) |
112 | and the core documentation (files in F<pod/>) |
113 | |
114 | =item 2 |
115 | |
116 | Work out how to split perlfunc into chunks, preferably one per function group, |
117 | preferably with general case code that could be used elsewhere. Challenges |
118 | here are correctly identifying the groups of functions that go together, and |
119 | making the right named external cross-links point to the right page. Things to |
120 | be aware of are C<-X>, groups such as C<getpwnam> to C<endservent>, two or |
121 | more C<=items> giving the different parameter lists, such as |
122 | |
123 | =item substr EXPR,OFFSET,LENGTH,REPLACEMENT |
124 | |
125 | =item substr EXPR,OFFSET,LENGTH |
126 | |
127 | =item substr EXPR,OFFSET |
128 | |
129 | and different parameter lists having different meanings. (eg C<select>) |
130 | |
131 | =back |
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132 | |
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133 | =head2 compressed man pages |
134 | |
135 | Be able to install them. This would probably need a configure test to see how |
136 | the system does compressed man pages (same directory/different directory? |
137 | same filename/different filename), as well as tweaking the F<installman> script |
138 | to compress as necessary. |
139 | |
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140 | =head2 Add a code coverage target to the Makefile |
141 | |
142 | Make it easy for anyone to run Devel::Cover on the core's tests. The steps |
143 | to do this manually are roughly |
144 | |
145 | =over 4 |
146 | |
147 | =item * |
148 | |
149 | do a normal C<Configure>, but include Devel::Cover as a module to install |
150 | (see F<INSTALL> for how to do this) |
151 | |
152 | =item * |
153 | |
154 | make perl |
155 | |
156 | =item * |
157 | |
158 | cd t; HARNESS_PERL_SWITCHES=-MDevel::Cover ./perl -I../lib harness |
159 | |
160 | =item * |
161 | |
162 | Process the resulting Devel::Cover database |
163 | |
164 | =back |
165 | |
166 | This just give you the coverage of the F<.pm>s. To also get the C level |
167 | coverage you need to |
168 | |
169 | =over 4 |
170 | |
171 | =item * |
172 | |
173 | Additionally tell C<Configure> to use the appropriate C compiler flags for |
174 | C<gcov> |
175 | |
176 | =item * |
177 | |
178 | make perl.gcov |
179 | |
180 | (instead of C<make perl>) |
181 | |
182 | =item * |
183 | |
184 | After running the tests run C<gcov> to generate all the F<.gcov> files. |
185 | (Including down in the subdirectories of F<ext/> |
186 | |
187 | =item * |
188 | |
189 | (From the top level perl directory) run C<gcov2perl> on all the C<.gcov> files |
190 | to get their stats into the cover_db directory. |
191 | |
192 | =item * |
193 | |
194 | Then process the Devel::Cover database |
195 | |
196 | =back |
197 | |
198 | It would be good to add a single switch to C<Configure> to specify that you |
199 | wanted to perform perl level coverage, and another to specify C level |
200 | coverage, and have C<Configure> and the F<Makefile> do all the right things |
201 | automatically. |
202 | |
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203 | =head2 Make Config.pm cope with differences between build and installed perl |
204 | |
205 | Quite often vendors ship a perl binary compiled with their (pay-for) |
206 | compilers. People install a free compiler, such as gcc. To work out how to |
207 | build extensions, Perl interrogates C<%Config>, so in this situation |
208 | C<%Config> describes compilers that aren't there, and extension building |
209 | fails. This forces people into choosing between re-compiling perl themselves |
210 | using the compiler they have, or only using modules that the vendor ships. |
211 | |
212 | It would be good to find a way teach C<Config.pm> about the installation setup, |
213 | possibly involving probing at install time or later, so that the C<%Config> in |
214 | a binary distribution better describes the installed machine, when the |
215 | installed machine differs from the build machine in some significant way. |
216 | |
217 | =head2 Relocatable perl |
218 | |
219 | The C level patches needed to create a relocatable perl binary are done, as |
220 | is the work on Config.pm. All that's left to do is the C<Configure> tweaking |
221 | to let people specify how they want to do the install. |
222 | |
223 | |
224 | |
225 | |
226 | |
227 | =head1 Tasks that need a little C knowledge |
228 | |
229 | These tasks would need a little C knowledge, but don't need any specific |
230 | background or experience with XS, or how the Perl interpreter works |
231 | |
232 | =head2 Make it clear from -v if this is the exact official release |
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233 | |
234 | Currently perl from p4/rsync ships with a patchlevel.h file that usually |
235 | defines one local patch, of the form "MAINT12345" or "RC1". The output of |
236 | perl -v doesn't report that a perl isn't an official release, and this |
237 | information can get lost in bugs reports. Because of this, the minor version |
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238 | isn't bumped up until RC time, to minimise the possibility of versions of perl |
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239 | escaping that believe themselves to be newer than they actually are. |
240 | |
241 | It would be useful to find an elegant way to have the "this is an interim |
242 | maintenance release" or "this is a release candidate" in the terse -v output, |
243 | and have it so that it's easy for the pumpking to remove this just as the |
244 | release tarball is rolled up. This way the version pulled out of rsync would |
245 | always say "I'm a development release" and it would be safe to bump the |
246 | reported minor version as soon as a release ships, which would aid perl |
247 | developers. |
248 | |
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249 | This task is really about thinking of an elegant way to arrange the C source |
250 | such that it's trivial for the Pumpking to flag "this is an official release" |
251 | when making a tarball, yet leave the default source saying "I'm not the |
252 | official release". |
253 | |
254 | =head2 bincompat functions |
255 | |
256 | There are lots of functions which are retained for binary compatibility. |
257 | Clean these up. Move them to mathom.c, and don't compile for blead? |
258 | |
259 | |
260 | |
261 | |
262 | |
263 | =head1 Tasks that need a knowledge of XS |
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264 | |
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265 | These tasks would need C knowledge, and roughly the level of knowledge of |
266 | the perl API that comes from writing modules that use XS to interface to |
267 | C. |
268 | |
269 | =head2 IPv6 |
270 | |
271 | Clean this up. Check everything in core works |
272 | |
273 | =head2 UTF8 caching code |
274 | |
275 | The string position/offset cache is not optional. It should be. |
276 | |
277 | =head2 Implicit Latin 1 => Unicode translation |
278 | |
279 | Conversions from byte strings to UTF-8 currently map high bit characters |
280 | to Unicode without translation (or, depending on how you look at it, by |
281 | implicitly assuming that the byte strings are in Latin-1). As perl assumes |
282 | the C locale by default, upgrading a string to UTF-8 may change the |
283 | meaning of its contents regarding character classes, case mapping, etc. |
284 | This should probably emit a warning (at least). |
285 | |
286 | This task is incremental - even a little bit of work on it will help. |
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287 | |
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288 | =head2 autovivification |
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289 | |
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290 | Make all autovivification consistent w.r.t LVALUE/RVALUE and strict/no strict; |
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291 | |
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292 | This task is incremental - even a little bit of work on it will help. |
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293 | |
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294 | =head2 Unicode in Filenames |
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295 | |
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296 | chdir, chmod, chown, chroot, exec, glob, link, lstat, mkdir, open, |
297 | opendir, qx, readdir, readlink, rename, rmdir, stat, symlink, sysopen, |
298 | system, truncate, unlink, utime, -X. All these could potentially accept |
299 | Unicode filenames either as input or output (and in the case of system |
300 | and qx Unicode in general, as input or output to/from the shell). |
301 | Whether a filesystem - an operating system pair understands Unicode in |
302 | filenames varies. |
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303 | |
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304 | Known combinations that have some level of understanding include |
305 | Microsoft NTFS, Apple HFS+ (In Mac OS 9 and X) and Apple UFS (in Mac |
306 | OS X), NFS v4 is rumored to be Unicode, and of course Plan 9. How to |
307 | create Unicode filenames, what forms of Unicode are accepted and used |
308 | (UCS-2, UTF-16, UTF-8), what (if any) is the normalization form used, |
309 | and so on, varies. Finding the right level of interfacing to Perl |
310 | requires some thought. Remember that an OS does not implicate a |
311 | filesystem. |
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312 | |
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313 | (The Windows -C command flag "wide API support" has been at least |
314 | temporarily retired in 5.8.1, and the -C has been repurposed, see |
315 | L<perlrun>.) |
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316 | |
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317 | =head2 Unicode in %ENV |
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318 | |
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319 | Currently the %ENV entries are always byte strings. |
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320 | |
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321 | =head2 use less 'memory' |
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322 | |
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323 | Investigate trade offs to switch out perl's choices on memory usage. |
324 | Particularly perl should be able to give memory back. |
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325 | |
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326 | This task is incremental - even a little bit of work on it will help. |
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327 | |
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328 | =head2 Re-implement C<:unique> in a way that is actually thread-safe |
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329 | |
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330 | The old implementation made bad assumptions on several levels. A good 90% |
331 | solution might be just to make C<:unique> work to share the string buffer |
332 | of SvPVs. That way large constant strings can be shared between ithreads, |
333 | such as the configuration information in F<Config>. |
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334 | |
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335 | =head2 Make tainting consistent |
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336 | |
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337 | Tainting would be easier to use if it didn't take documented shortcuts and |
338 | allow taint to "leak" everywhere within an expression. |
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339 | |
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340 | =head2 readpipe(LIST) |
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341 | |
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342 | system() accepts a LIST syntax (and a PROGRAM LIST syntax) to avoid |
343 | running a shell. readpipe() (the function behind qx//) could be similarly |
344 | extended. |
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345 | |
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346 | |
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347 | |
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348 | |
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349 | |
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350 | =head1 Tasks that need a knowledge of the interpreter |
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351 | |
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352 | These tasks would need C knowledge, and knowledge of how the interpreter works, |
353 | or a willingness to learn. |
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354 | |
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355 | =head2 lexical pragmas |
356 | |
357 | Reimplement the mechanism of lexical pragmas to be more extensible. Fix |
358 | current pragmas that don't work well (or at all) with lexical scopes or in |
359 | run-time eval(STRING) (C<sort>, C<re>, C<encoding> for example). MJD has a |
360 | preliminary patch that implements this. |
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361 | |
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362 | =head2 Attach/detach debugger from running program |
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363 | |
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364 | The old perltodo notes "With C<gdb>, you can attach the debugger to a running |
365 | program if you pass the process ID. It would be good to do this with the Perl |
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366 | debugger on a running Perl program, although I'm not sure how it would be |
367 | done." ssh and screen do this with named pipes in /tmp. Maybe we can too. |
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368 | |
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369 | =head2 inlining autoloaded constants |
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370 | |
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371 | Currently the optimiser can inline constants when expressed as subroutines |
372 | with prototype ($) that return a constant. Likewise, many packages wrapping |
373 | C libraries export lots of constants as subroutines which are AUTOLOADed on |
374 | demand. However, these have no prototypes, so can't be seen as constants by |
375 | the optimiser. Some way of cheaply (low syntax, low memory overhead) to the |
376 | perl compiler that a name is a constant would be great, so that it knows to |
377 | call the AUTOLOAD routine at compile time, and then inline the constant. |
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378 | |
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379 | =head2 Constant folding |
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380 | |
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381 | The peephole optimiser should trap errors during constant folding, and give |
382 | up on the folding, rather than bailing out at compile time. It is quite |
383 | possible that the unfoldable constant is in unreachable code, eg something |
384 | akin to C<$a = 0/0 if 0;> |
385 | |
386 | =head2 LVALUE functions for lists |
387 | |
388 | The old perltodo notes that lvalue functions don't work for list or hash |
389 | slices. This would be good to fix. |
390 | |
391 | =head2 LVALUE functions in the debugger |
392 | |
393 | The old perltodo notes that lvalue functions don't work in the debugger. This |
394 | would be good to fix. |
395 | |
396 | =head2 _ prototype character |
397 | |
398 | Study the possibility of adding a new prototype character, C<_>, meaning |
399 | "this argument defaults to $_". |
400 | |
401 | =head2 @INC source filter to Filter::Simple |
402 | |
403 | The second return value from a sub in @INC can be a source filter. This isn't |
404 | documented. It should be changed to use Filter::Simple, tested and documented. |
405 | |
406 | =head2 regexp optimiser optional |
407 | |
408 | The regexp optimiser is not optional. It should configurable to be, to allow |
409 | its performance to be measured, and its bugs to be easily demonstrated. |
410 | |
411 | =head2 UNITCHECK |
412 | |
413 | Introduce a new special block, UNITCHECK, which is run at the end of a |
414 | compilation unit (module, file, eval(STRING) block). This will correspond to |
415 | the Perl 6 CHECK. Perl 5's CHECK cannot be changed or removed because the |
416 | O.pm/B.pm backend framework depends on it. |
417 | |
418 | =head2 optional optimizer |
419 | |
420 | Make the peephole optimizer optional. Currently it performs two tasks as |
421 | it walks the optree - genuine peephole optimisations, and necessary fixups of |
422 | ops. It would be good to find an efficient way to switch out the |
423 | optimisations whilst keeping the fixups. |
424 | |
425 | =head2 You WANT *how* many |
426 | |
427 | Currently contexts are void, scalar and list. split has a special mechanism in |
428 | place to pass in the number of return values wanted. It would be useful to |
429 | have a general mechanism for this, backwards compatible and little speed hit. |
430 | This would allow proposals such as short circuiting sort to be implemented |
431 | as a module on CPAN. |
432 | |
433 | =head2 lexical aliases |
434 | |
435 | Allow lexical aliases (maybe via the syntax C<my \$alias = \$foo>. |
436 | |
437 | =head2 entersub XS vs Perl |
438 | |
439 | At the moment pp_entersub is huge, and has code to deal with entering both |
440 | perl and XS subroutines. Subroutine implementations rarely change between |
441 | perl and XS at run time, so investigate using 2 ops to enter subs (one for |
442 | XS, one for perl) and swap between if a sub is redefined. |
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443 | |
444 | =head2 Self ties |
445 | |
446 | self ties are currently illegal because they caused too many segfaults. Maybe |
447 | the causes of these could be tracked down and self-ties on all types re- |
448 | instated. |
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449 | |
450 | =head2 Optimize away @_ |
451 | |
452 | The old perltodo notes "Look at the "reification" code in C<av.c>". |
453 | |
454 | =head2 switch ops |
455 | |
456 | The old perltodo notes "Although we have C<Switch.pm> in core, Larry points to |
457 | the dormant C<nswitch> and C<cswitch> ops in F<pp.c>; using these opcodes would |
458 | be much faster." |
459 | |
460 | =head2 What hooks would assertions need? |
461 | |
462 | Assertions are in the core, and work. However, assertions needed to be added |
463 | as a core patch, rather than an XS module in ext, or a CPAN module, because |
464 | the core has no hooks in the necessary places. It would be useful to |
465 | investigate what hooks would need to be added to make it possible to provide |
466 | the full assertion support from a CPAN module, so that we aren't constraining |
467 | the imagination of future CPAN authors. |
468 | |
469 | |
470 | |
471 | |
472 | |
473 | |
474 | |
475 | =head1 Big projects |
476 | |
477 | Tasks that will get your name mentioned in the description of the "Highlights |
478 | of 5.10" |
479 | |
480 | =head2 make ithreads more robust |
481 | |
482 | Generally make ithreads more robust. See also L<iCOW> |
483 | |
484 | This task is incremental - even a little bit of work on it will help, and |
485 | will be greatly appreciated. |
486 | |
487 | =head2 iCOW |
488 | |
489 | Sarathy and Arthur have a proposal for an improved Copy On Write which |
490 | specifically will be able to COW new ithreads. If this can be implemented |
491 | it would be a good thing. |
492 | |
493 | =head2 (?{...}) closures in regexps |
494 | |
495 | Fix (or rewrite) the implementation of the C</(?{...})/> closures. |
496 | |
497 | =head2 A re-entrant regexp engine |
498 | |
499 | This will allow the use of a regex from inside (?{ }), (??{ }) and |
500 | (?(?{ })|) constructs. |