3 perltodo - Perl TO-DO List
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.
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:
16 http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/
22 =head1 Tasks that only need Perl knowledge
24 =head2 common test code for timed bail out
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.
30 =head2 POD -> HTML conversion in the core still sucks
32 Which is crazy given just how simple POD purports to be, and how simple HTML
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.
39 =head2 Make Schwern poorer
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
46 See F<t/lib/1_compile.t> for the 3 remaining modules that need tests.
48 =head2 Improve the coverage of the core tests
50 Use Devel::Cover to ascertain the core's test coverage, then add tests that
51 are currently missing.
54 A full test suite for the B module would be nice.
56 =head2 A decent benchmark
58 perlbench seems impervious to any recent changes made to the perl core. It
59 would be useful to have a reasonable general benchmarking suite that roughly
60 represented what current perl programs do, and measurably reported whether
61 tweaks to the core improve, degrade or don't really affect performance, to
62 guide people attempting to optimise the guts of perl. Gisle would welcome
63 new tests for perlbench.
65 =head2 fix tainting bugs
67 Fix the bugs revealed by running the test suite with the C<-t> switch (via
68 C<make test.taintwarn>).
70 =head2 Dual life everything
72 As part of the "dists" plan, anything that doesn't belong in the smallest perl
73 distribution needs to be dual lifed. Anything else can be too. Figure out what
74 changes would be needed to package that module and its tests up for CPAN, and
75 do so. Test it with older perl releases, and fix the problems you find.
77 =head2 Improving C<threads::shared>
79 Investigate whether C<threads::shared> could share aggregates properly with
80 only Perl level changes to shared.pm
82 =head2 POSIX memory footprint
84 Ilya observed that use POSIX; eats memory like there's no tomorrow, and at
85 various times worked to cut it down. There is probably still fat to cut out -
86 for example POSIX passes Exporter some very memory hungry data structures.
94 =head1 Tasks that need a little sysadmin-type knowledge
96 Or if you prefer, tasks that you would learn from, and broaden your skills
99 =head2 make HTML install work
101 There is an C<installhtml> target in the Makefile. It's marked as
102 "experimental". It would be good to get this tested, make it work reliably, and
103 remove the "experimental" tag. This would include
109 Checking that cross linking between various parts of the documentation works.
110 In particular that links work between the modules (files with POD in F<lib/>)
111 and the core documentation (files in F<pod/>)
115 Work out how to split perlfunc into chunks, preferably one per function group,
116 preferably with general case code that could be used elsewhere. Challenges
117 here are correctly identifying the groups of functions that go together, and
118 making the right named external cross-links point to the right page. Things to
119 be aware of are C<-X>, groups such as C<getpwnam> to C<endservent>, two or
120 more C<=items> giving the different parameter lists, such as
122 =item substr EXPR,OFFSET,LENGTH,REPLACEMENT
124 =item substr EXPR,OFFSET,LENGTH
126 =item substr EXPR,OFFSET
128 and different parameter lists having different meanings. (eg C<select>)
132 =head2 compressed man pages
134 Be able to install them. This would probably need a configure test to see how
135 the system does compressed man pages (same directory/different directory?
136 same filename/different filename), as well as tweaking the F<installman> script
137 to compress as necessary.
139 =head2 Make Config.pm cope with differences between build and installed perl
141 Quite often vendors ship a perl binary compiled with their (pay-for)
142 compilers. People install a free compiler, such as gcc. To work out how to
143 build extensions, Perl interrogates C<%Config>, so in this situation
144 C<%Config> describes compilers that aren't there, and extension building
145 fails. This forces people into choosing between re-compiling perl themselves
146 using the compiler they have, or only using modules that the vendor ships.
148 It would be good to find a way teach C<Config.pm> about the installation setup,
149 possibly involving probing at install time or later, so that the C<%Config> in
150 a binary distribution better describes the installed machine, when the
151 installed machine differs from the build machine in some significant way.
153 =head2 Relocatable perl
155 The C level patches needed to create a relocatable perl binary are done, as
156 is the work on Config.pm. All that's left to do is the C<Configure> tweaking
157 to let people specify how they want to do the install.
163 =head1 Tasks that need a little C knowledge
165 These tasks would need a little C knowledge, but don't need any specific
166 background or experience with XS, or how the Perl interpreter works
168 =head2 Make it clear from -v if this is the exact official release
170 Currently perl from p4/rsync ships with a patchlevel.h file that usually
171 defines one local patch, of the form "MAINT12345" or "RC1". The output of
172 perl -v doesn't report that a perl isn't an official release, and this
173 information can get lost in bugs reports. Because of this, the minor version
174 isn't bumped up until RC time, to minimise the possibility of versions of perl
175 escaping that believe themselves to be newer than they actually are.
177 It would be useful to find an elegant way to have the "this is an interim
178 maintenance release" or "this is a release candidate" in the terse -v output,
179 and have it so that it's easy for the pumpking to remove this just as the
180 release tarball is rolled up. This way the version pulled out of rsync would
181 always say "I'm a development release" and it would be safe to bump the
182 reported minor version as soon as a release ships, which would aid perl
185 This task is really about thinking of an elegant way to arrange the C source
186 such that it's trivial for the Pumpking to flag "this is an official release"
187 when making a tarball, yet leave the default source saying "I'm not the
190 =head2 bincompat functions
192 There are lots of functions which are retained for binary compatibility.
193 Clean these up. Move them to mathom.c, and don't compile for blead?
199 =head1 Tasks that need a knowledge of XS
201 These tasks would need C knowledge, and roughly the level of knowledge of
202 the perl API that comes from writing modules that use XS to interface to
207 Clean this up. Check everything in core works
209 =head2 UTF8 caching code
211 The string position/offset cache is not optional. It should be.
213 =head2 Implicit Latin 1 => Unicode translation
215 Conversions from byte strings to UTF-8 currently map high bit characters
216 to Unicode without translation (or, depending on how you look at it, by
217 implicitly assuming that the byte strings are in Latin-1). As perl assumes
218 the C locale by default, upgrading a string to UTF-8 may change the
219 meaning of its contents regarding character classes, case mapping, etc.
220 This should probably emit a warning (at least).
222 This task is incremental - even a little bit of work on it will help.
224 =head2 autovivification
226 Make all autovivification consistent w.r.t LVALUE/RVALUE and strict/no strict;
228 This task is incremental - even a little bit of work on it will help.
230 =head2 Unicode in Filenames
232 chdir, chmod, chown, chroot, exec, glob, link, lstat, mkdir, open,
233 opendir, qx, readdir, readlink, rename, rmdir, stat, symlink, sysopen,
234 system, truncate, unlink, utime, -X. All these could potentially accept
235 Unicode filenames either as input or output (and in the case of system
236 and qx Unicode in general, as input or output to/from the shell).
237 Whether a filesystem - an operating system pair understands Unicode in
240 Known combinations that have some level of understanding include
241 Microsoft NTFS, Apple HFS+ (In Mac OS 9 and X) and Apple UFS (in Mac
242 OS X), NFS v4 is rumored to be Unicode, and of course Plan 9. How to
243 create Unicode filenames, what forms of Unicode are accepted and used
244 (UCS-2, UTF-16, UTF-8), what (if any) is the normalization form used,
245 and so on, varies. Finding the right level of interfacing to Perl
246 requires some thought. Remember that an OS does not implicate a
249 (The Windows -C command flag "wide API support" has been at least
250 temporarily retired in 5.8.1, and the -C has been repurposed, see
253 =head2 Unicode in %ENV
255 Currently the %ENV entries are always byte strings.
257 =head2 use less 'memory'
259 Investigate trade offs to switch out perl's choices on memory usage.
260 Particularly perl should be able to give memory back.
262 This task is incremental - even a little bit of work on it will help.
264 =head2 Re-implement C<:unique> in a way that is actually thread-safe
266 The old implementation made bad assumptions on several levels. A good 90%
267 solution might be just to make C<:unique> work to share the string buffer
268 of SvPVs. That way large constant strings can be shared between ithreads,
269 such as the configuration information in F<Config>.
271 =head2 Make tainting consistent
273 Tainting would be easier to use if it didn't take documented shortcuts and
274 allow taint to "leak" everywhere within an expression.
276 =head2 readpipe(LIST)
278 system() accepts a LIST syntax (and a PROGRAM LIST syntax) to avoid
279 running a shell. readpipe() (the function behind qx//) could be similarly
286 =head1 Tasks that need a knowledge of the interpreter
288 These tasks would need C knowledge, and knowledge of how the interpreter works,
289 or a willingness to learn.
291 =head2 lexical pragmas
293 Reimplement the mechanism of lexical pragmas to be more extensible. Fix
294 current pragmas that don't work well (or at all) with lexical scopes or in
295 run-time eval(STRING) (C<sort>, C<re>, C<encoding> for example). MJD has a
296 preliminary patch that implements this.
298 =head2 Attach/detach debugger from running program
300 The old perltodo notes "With C<gdb>, you can attach the debugger to a running
301 program if you pass the process ID. It would be good to do this with the Perl
302 debugger on a running Perl program, although I'm not sure how it would be
303 done." ssh and screen do this with named pipes in /tmp. Maybe we can too.
305 =head2 inlining autoloaded constants
307 Currently the optimiser can inline constants when expressed as subroutines
308 with prototype ($) that return a constant. Likewise, many packages wrapping
309 C libraries export lots of constants as subroutines which are AUTOLOADed on
310 demand. However, these have no prototypes, so can't be seen as constants by
311 the optimiser. Some way of cheaply (low syntax, low memory overhead) to the
312 perl compiler that a name is a constant would be great, so that it knows to
313 call the AUTOLOAD routine at compile time, and then inline the constant.
315 =head2 Constant folding
317 The peephole optimiser should trap errors during constant folding, and give
318 up on the folding, rather than bailing out at compile time. It is quite
319 possible that the unfoldable constant is in unreachable code, eg something
320 akin to C<$a = 0/0 if 0;>
322 =head2 LVALUE functions for lists
324 The old perltodo notes that lvalue functions don't work for list or hash
325 slices. This would be good to fix.
327 =head2 LVALUE functions in the debugger
329 The old perltodo notes that lvalue functions don't work in the debugger. This
330 would be good to fix.
332 =head2 _ prototype character
334 Study the possibility of adding a new prototype character, C<_>, meaning
335 "this argument defaults to $_".
337 =head2 @INC source filter to Filter::Simple
339 The second return value from a sub in @INC can be a source filter. This isn't
340 documented. It should be changed to use Filter::Simple, tested and documented.
342 =head2 regexp optimiser optional
344 The regexp optimiser is not optional. It should configurable to be, to allow
345 its performance to be measured, and its bugs to be easily demonstrated.
349 Introduce a new special block, UNITCHECK, which is run at the end of a
350 compilation unit (module, file, eval(STRING) block). This will correspond to
351 the Perl 6 CHECK. Perl 5's CHECK cannot be changed or removed because the
352 O.pm/B.pm backend framework depends on it.
354 =head2 optional optimizer
356 Make the peephole optimizer optional. Currently it performs two tasks as
357 it walks the optree - genuine peephole optimisations, and necessary fixups of
358 ops. It would be good to find an efficient way to switch out the
359 optimisations whilst keeping the fixups.
361 =head2 You WANT *how* many
363 Currently contexts are void, scalar and list. split has a special mechanism in
364 place to pass in the number of return values wanted. It would be useful to
365 have a general mechanism for this, backwards compatible and little speed hit.
366 This would allow proposals such as short circuiting sort to be implemented
369 =head2 lexical aliases
371 Allow lexical aliases (maybe via the syntax C<my \$alias = \$foo>.
373 =head2 entersub XS vs Perl
375 At the moment pp_entersub is huge, and has code to deal with entering both
376 perl and XS subroutines. Subroutine implementations rarely change between
377 perl and XS at run time, so investigate using 2 ops to enter subs (one for
378 XS, one for perl) and swap between if a sub is redefined.
382 self ties are currently illegal because they caused too many segfaults. Maybe
383 the causes of these could be tracked down and self-ties on all types re-
386 =head2 Optimize away @_
388 The old perltodo notes "Look at the "reification" code in C<av.c>".
392 The old perltodo notes "Although we have C<Switch.pm> in core, Larry points to
393 the dormant C<nswitch> and C<cswitch> ops in F<pp.c>; using these opcodes would
396 =head2 What hooks would assertions need?
398 Assertions are in the core, and work. However, assertions needed to be added
399 as a core patch, rather than an XS module in ext, or a CPAN module, because
400 the core has no hooks in the necessary places. It would be useful to
401 investigate what hooks would need to be added to make it possible to provide
402 the full assertion support from a CPAN module, so that we aren't constraining
403 the imagination of future CPAN authors.
413 Tasks that will get your name mentioned in the description of the "Highlights
416 =head2 make ithreads more robust
418 Generally make ithreads more robust. See also L<iCOW>
420 This task is incremental - even a little bit of work on it will help, and
421 will be greatly appreciated.
425 Sarathy and Arthur have a proposal for an improved Copy On Write which
426 specifically will be able to COW new ithreads. If this can be implemented
427 it would be a good thing.
429 =head2 (?{...}) closures in regexps
431 Fix (or rewrite) the implementation of the C</(?{...})/> closures.
433 =head2 A re-entrant regexp engine
435 This will allow the use of a regex from inside (?{ }), (??{ }) and
436 (?(?{ })|) constructs.