=head1 DESCRIPTION
-This is a list of wishes for Perl. Send updates to
-I<perl5-porters@perl.org>. If you want to work on any of these
-projects, be sure to check the perl5-porters archives for past ideas,
-flames, and propaganda. This will save you time and also prevent you
-from implementing something that Larry has already vetoed. One set
-of archives may be found at:
+This is a list of wishes for Perl. The tasks we think are smaller or easier
+are listed first. Anyone is welcome to work on any of these, but it's a good
+idea to first contact I<perl5-porters@perl.org> to avoid duplication of
+effort. By all means contact a pumpking privately first if you prefer.
+
+Whilst patches to make the list shorter are most welcome, ideas to add to
+the list are also encouraged. Check the perl5-porters archives for past
+ideas, and any discussion about them. One set of archives may be found at:
http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/
-=head1 assertions
+What can we offer you in return? Fame, fortune, and everlasting glory? Maybe
+not, but if your patch is incorporated, then we'll add your name to the
+F<AUTHORS> file, which ships in the official distribution. How many other
+programming languages offer you 1 line of immortality?
-Clean up and finish support for assertions. See L<assertions>.
+=head1 The roadmap to 5.10
-=head1 iCOW
+The roadmap to 5.10 envisages feature based releases, as various items in this
+TODO are completed.
-Sarathy and Arthur have a proposal for an improved Copy On Write which
-specifically will be able to COW new ithreads. If this can be implemented
-it would be a good thing.
+=head2 Needed for the final 5.10.0 release
-=head1 (?{...}) closures in regexps
+Review perlguts. Significant changes have occured since 5.8, and we can't
+release a new version without making sure these are covered.
-Fix (or rewrite) the implementation of the C</(?{...})/> closures.
+=head1 Tasks that only need Perl knowledge
-=head1 A re-entrant regexp engine
+=head2 common test code for timed bail out
-This will allow the use of a regex from inside (?{ }), (??{ }) and
-(?(?{ })|) constructs.
+Write portable self destruct code for tests to stop them burning CPU in
+infinite loops. This needs to avoid using alarm, as some of the tests are
+testing alarm/sleep or timers.
-=head1 pragmata
+=head2 POD -> HTML conversion in the core still sucks
-=head2 lexical pragmas
+Which is crazy given just how simple POD purports to be, and how simple HTML
+can be. It's not actually I<as> simple as it sounds, particularly with the
+flexibility POD allows for C<=item>, but it would be good to improve the
+visual appeal of the HTML generated, and to avoid it having any validation
+errors. See also L</make HTML install work>, as the layout of installation tree
+is needed to improve the cross-linking.
-Reimplement the mechanism of lexical pragmas to be more extensible. Fix
-current pragmas that don't work well (or at all) with lexical scopes or in
-run-time eval(STRING) (C<sort>, C<re>, C<encoding> for example). MJD has a
-preliminary patch that implements this.
+The addition of C<Pod::Simple> and its related modules may make this task
+easier to complete.
-=head2 use less 'memory'
+=head2 Parallel testing
-Investigate trade offs to switch out perl's choices on memory usage.
-Particularly perl should be able to give memory back.
+(This probably impacts much more than the core: also the Test::Harness
+and TAP::* modules on CPAN.)
-=head1 prototypes and functions
+The core regression test suite is getting ever more comprehensive, which has
+the side effect that it takes longer to run. This isn't so good. Investigate
+whether it would be feasible to give the harness script the B<option> of
+running sets of tests in parallel. This would be useful for tests in
+F<t/op/*.t> and F<t/uni/*.t> and maybe some sets of tests in F<lib/>.
-=head2 _ prototype character
+Questions to answer
-Study the possibility of adding a new prototype character, C<_>, meaning
-"this argument defaults to $_".
+=over 4
-=head2 inlining autoloaded constants
+=item 1
-Currently the optimiser can inline constants when expressed as subroutines
-with prototype ($) that return a constant. Likewise, many packages wrapping
-C libraries export lots of constants as subroutines which are AUTOLOADed on
-demand. However, these have no prototypes, so can't be seen as constants by
-the optimiser. Some way of cheaply (low syntax, low memory overhead) to the
-perl compiler that a name is a constant would be great, so that it knows to
-call the AUTOLOAD routine at compile time, and then inline the constant.
+How does screen layout work when you're running more than one test?
-=head2 Finish off lvalue functions
+=item 2
-The old perltodo notes "They don't work in the debugger, and they don't work for
-list or hash slices."
+How does the caller of test specify how many tests to run in parallel?
-=head1 Unicode and UTF8
+=item 3
-=head2 Implicit Latin 1 => Unicode translation
+How do setup/teardown tests identify themselves?
-Conversions from byte strings to UTF-8 currently map high bit characters
-to Unicode without translation (or, depending on how you look at it, by
-implicitly assuming that the byte strings are in Latin-1). As perl assumes
-the C locale by default, upgrading a string to UTF-8 may change the
-meaning of its contents regarding character classes, case mapping, etc.
-This should probably emit a warning (at least).
+=back
-=head2 UTF8 caching code
+Pugs already does parallel testing - can their approach be re-used?
-The string position/offset cache is not optional. It should be.
+=head2 Make Schwern poorer
-=head2 Unicode in Filenames
+We should have tests for everything. When all the core's modules are tested,
+Schwern has promised to donate to $500 to TPF. We may need volunteers to
+hold him upside down and shake vigorously in order to actually extract the
+cash.
-chdir, chmod, chown, chroot, exec, glob, link, lstat, mkdir, open,
-opendir, qx, readdir, readlink, rename, rmdir, stat, symlink, sysopen,
-system, truncate, unlink, utime, -X. All these could potentially accept
-Unicode filenames either as input or output (and in the case of system
-and qx Unicode in general, as input or output to/from the shell).
-Whether a filesystem - an operating system pair understands Unicode in
-filenames varies.
+=head2 Improve the coverage of the core tests
-Known combinations that have some level of understanding include
-Microsoft NTFS, Apple HFS+ (In Mac OS 9 and X) and Apple UFS (in Mac
-OS X), NFS v4 is rumored to be Unicode, and of course Plan 9. How to
-create Unicode filenames, what forms of Unicode are accepted and used
-(UCS-2, UTF-16, UTF-8), what (if any) is the normalization form used,
-and so on, varies. Finding the right level of interfacing to Perl
-requires some thought. Remember that an OS does not implicate a
-filesystem.
+Use Devel::Cover to ascertain the core modules's test coverage, then add
+tests that are currently missing.
-(The Windows -C command flag "wide API support" has been at least
-temporarily retired in 5.8.1, and the -C has been repurposed, see
-L<perlrun>.)
+=head2 test B
-=head2 Unicode in %ENV
+A full test suite for the B module would be nice.
-Currently the %ENV entries are always byte strings.
+=head2 A decent benchmark
-=head1 Regexps
+C<perlbench> seems impervious to any recent changes made to the perl core. It
+would be useful to have a reasonable general benchmarking suite that roughly
+represented what current perl programs do, and measurably reported whether
+tweaks to the core improve, degrade or don't really affect performance, to
+guide people attempting to optimise the guts of perl. Gisle would welcome
+new tests for perlbench.
-=head2 regexp optimiser optional
+=head2 fix tainting bugs
-The regexp optimiser is not optional. It should configurable to be, to allow
-its performance to be measured, and its bugs to be easily demonstrated.
+Fix the bugs revealed by running the test suite with the C<-t> switch (via
+C<make test.taintwarn>).
-=head2 common suffices/prefices in regexps (trie optimization)
+=head2 Dual life everything
-Currently, the user has to optimize C<foo|far> and C<foo|goo> into
-C<f(?:oo|ar)> and C<[fg]oo> by hand; this could be done automatically.
+As part of the "dists" plan, anything that doesn't belong in the smallest perl
+distribution needs to be dual lifed. Anything else can be too. Figure out what
+changes would be needed to package that module and its tests up for CPAN, and
+do so. Test it with older perl releases, and fix the problems you find.
-=head1 POD
+=head2 Improving C<threads::shared>
-=head2 POD -> HTML conversion still sucks
+Investigate whether C<threads::shared> could share aggregates properly with
+only Perl level changes to shared.pm
-Which is crazy given just how simple POD purports to be, and how simple HTML
-can be.
+=head2 POSIX memory footprint
-=head1 Misc medium sized projects
+Ilya observed that use POSIX; eats memory like there's no tomorrow, and at
+various times worked to cut it down. There is probably still fat to cut out -
+for example POSIX passes Exporter some very memory hungry data structures.
-=head2 UNITCHECK
+=head2 embed.pl/makedef.pl
-Introduce a new special block, UNITCHECK, which is run at the end of a
-compilation unit (module, file, eval(STRING) block). This will correspond to
-the Perl 6 CHECK. Perl 5's CHECK cannot be changed or removed because the
-O.pm/B.pm backend framework depends on it.
+There is a script F<embed.pl> that generates several header files to prefix
+all of Perl's symbols in a consistent way, to provide some semblance of
+namespace support in C<C>. Functions are declared in F<embed.fnc>, variables
+in F<interpvar.h> and F<thrdvar.h>. Quite a few of the functions and variables
+are conditionally declared there, using C<#ifdef>. However, F<embed.pl>
+doesn't understand the C macros, so the rules about which symbols are present
+when is duplicated in F<makedef.pl>. Writing things twice is bad, m'kay.
+It would be good to teach C<embed.pl> to understand the conditional
+compilation, and hence remove the duplication, and the mistakes it has caused.
-=head2 optional optimizer
+=head1 Tasks that need a little sysadmin-type knowledge
-Make the peephole optimizer optional.
+Or if you prefer, tasks that you would learn from, and broaden your skills
+base...
-=head2 You WANT *how* many
+=head2 make HTML install work
-Currently contexts are void, scalar and list. split has a special mechanism in
-place to pass in the number of return values wanted. It would be useful to
-have a general mechanism for this, backwards compatible and little speed hit.
-This would allow proposals such as short circuiting sort to be implemented
-as a module on CPAN.
+There is an C<installhtml> target in the Makefile. It's marked as
+"experimental". It would be good to get this tested, make it work reliably, and
+remove the "experimental" tag. This would include
-=head2 lexical aliases
+=over 4
-Allow lexical aliases (maybe via the syntax C<my \$alias = \$foo>.
+=item 1
-=head2 no 6
+Checking that cross linking between various parts of the documentation works.
+In particular that links work between the modules (files with POD in F<lib/>)
+and the core documentation (files in F<pod/>)
-Make C<no 6> and C<no v6> work (opposite of C<use 5.005>, etc.).
+=item 2
-=head2 IPv6
+Work out how to split C<perlfunc> into chunks, preferably one per function
+group, preferably with general case code that could be used elsewhere.
+Challenges here are correctly identifying the groups of functions that go
+together, and making the right named external cross-links point to the right
+page. Things to be aware of are C<-X>, groups such as C<getpwnam> to
+C<endservent>, two or more C<=items> giving the different parameter lists, such
+as
-Clean this up. Check everything in core works
+ =item substr EXPR,OFFSET,LENGTH,REPLACEMENT
+ =item substr EXPR,OFFSET,LENGTH
+ =item substr EXPR,OFFSET
-=head2 entersub XS vs Perl
+and different parameter lists having different meanings. (eg C<select>)
-At the moment pp_entersub is huge, and has code to deal with entering both
-perl and and XS subroutines. Subroutine implementations rarely change between
-perl and XS at run time, so investigate using 2 ops to enter subs (one for
-XS, one for perl) and swap between if a sub is redefined.
+=back
-=head2 @INC source filter to Filter::Simple
+=head2 compressed man pages
-The second return value from a sub in @INC can be a source filter. This isn't
-documented. It should be changed to use Filter::Simple, tested and documented.
+Be able to install them. This would probably need a configure test to see how
+the system does compressed man pages (same directory/different directory?
+same filename/different filename), as well as tweaking the F<installman> script
+to compress as necessary.
-=head2 bincompat functions
+=head2 Add a code coverage target to the Makefile
-There are lots of functions which are retained for binary compatibility.
-Clean these up. Move them to mathom.c, and don't compile for blead?
+Make it easy for anyone to run Devel::Cover on the core's tests. The steps
+to do this manually are roughly
-=head2 Use fchown/fchmod internally
+=over 4
-The old perltodo notes "This has been done in places, but needs a thorough
-code review. Also fchdir is available in some platforms."
+=item *
-=head1 Tests
+do a normal C<Configure>, but include Devel::Cover as a module to install
+(see F<INSTALL> for how to do this)
-=head2 Make Schwern poorer
+=item *
-Tests for everything, At which point Schwern coughs up $500 to TPF.
+ make perl
-=head2 test B
+=item *
-A test suite for the B module would be nice.
+ cd t; HARNESS_PERL_SWITCHES=-MDevel::Cover ./perl -I../lib harness
-=head2 common test code for timed bailout
+=item *
-Write portable self destruct code for tests to stop them burning CPU in
-infinite loops. Needs to avoid using alarm, as some of the tests are testing
-alarm/sleep or timers.
+Process the resulting Devel::Cover database
-=head1 Installation
+=back
-=head2 compressed man pages
+This just give you the coverage of the F<.pm>s. To also get the C level
+coverage you need to
-Be able to install them
+=over 4
-=head2 Make Config.pm cope with differences between build and installed perl
+=item *
-=head2 Relocatable perl
+Additionally tell C<Configure> to use the appropriate C compiler flags for
+C<gcov>
-Make it possible to create a relocatable perl binary. Will need some collusion
-with Config.pm. We could use a syntax of ... for location of current binary?
+=item *
-=head2 make HTML install work
+ make perl.gcov
+
+(instead of C<make perl>)
+
+=item *
+
+After running the tests run C<gcov> to generate all the F<.gcov> files.
+(Including down in the subdirectories of F<ext/>
+
+=item *
+
+(From the top level perl directory) run C<gcov2perl> on all the C<.gcov> files
+to get their stats into the cover_db directory.
+
+=item *
+
+Then process the Devel::Cover database
+
+=back
+
+It would be good to add a single switch to C<Configure> to specify that you
+wanted to perform perl level coverage, and another to specify C level
+coverage, and have C<Configure> and the F<Makefile> do all the right things
+automatically.
+
+=head2 Make Config.pm cope with differences between built and installed perl
+
+Quite often vendors ship a perl binary compiled with their (pay-for)
+compilers. People install a free compiler, such as gcc. To work out how to
+build extensions, Perl interrogates C<%Config>, so in this situation
+C<%Config> describes compilers that aren't there, and extension building
+fails. This forces people into choosing between re-compiling perl themselves
+using the compiler they have, or only using modules that the vendor ships.
+
+It would be good to find a way teach C<Config.pm> about the installation setup,
+possibly involving probing at install time or later, so that the C<%Config> in
+a binary distribution better describes the installed machine, when the
+installed machine differs from the build machine in some significant way.
+
+=head2 linker specification files
+
+Some platforms mandate that you provide a list of a shared library's external
+symbols to the linker, so the core already has the infrastructure in place to
+do this for generating shared perl libraries. My understanding is that the
+GNU toolchain can accept an optional linker specification file, and restrict
+visibility just to symbols declared in that file. It would be good to extend
+F<makedef.pl> to support this format, and to provide a means within
+C<Configure> to enable it. This would allow Unix users to test that the
+export list is correct, and to build a perl that does not pollute the global
+namespace with private symbols.
+
+=head2 Cross-compile support
+
+Currently C<Configure> understands C<-Dusecrosscompile> option. This option
+arranges for building C<miniperl> for TARGET machine, so this C<miniperl> is
+assumed then to be copied to TARGET machine and used as a replacement of full
+C<perl> executable.
+
+This could be done little differently. Namely C<miniperl> should be built for
+HOST and then full C<perl> with extensions should be compiled for TARGET.
+This, however, might require extra trickery for %Config: we have one config
+first for HOST and then another for TARGET.
+
+=head1 Tasks that need a little C knowledge
+
+These tasks would need a little C knowledge, but don't need any specific
+background or experience with XS, or how the Perl interpreter works
-=head2 put patchlevel in -v
+=head2 Make it clear from -v if this is the exact official release
-Currently perl from p4/rsync ships with a patchlevel.h file that usually
-defines one local patch, of the form "MAINT12345" or "RC1". The output of
-perl -v doesn't report that a perl isn't an official release, and this
+Currently perl from C<p4>/C<rsync> ships with a F<patchlevel.h> file that
+usually defines one local patch, of the form "MAINT12345" or "RC1". The output
+of perl -v doesn't report that a perl isn't an official release, and this
information can get lost in bugs reports. Because of this, the minor version
isn't bumped up until RC time, to minimise the possibility of versions of perl
escaping that believe themselves to be newer than they actually are.
reported minor version as soon as a release ships, which would aid perl
developers.
-=head1 Incremental things
+This task is really about thinking of an elegant way to arrange the C source
+such that it's trivial for the Pumpking to flag "this is an official release"
+when making a tarball, yet leave the default source saying "I'm not the
+official release".
-Some tasks that don't need to get done in one big hit.
+=head2 Ordering of "global" variables.
+
+F<thrdvar.h> and F<intrpvarh> define the "global" variables that need to be
+per-thread under ithreads, where the variables are actually elements in a
+structure. As C dictates, the variables must be laid out in order of
+declaration. There is a comment
+C</* Important ones in the first cache line (if alignment is done right) */>
+which implies that at some point in the past the ordering was carefully chosen
+(at least in part). However, it's clear that the ordering is less than perfect,
+as currently there are things such as 7 C<bool>s in a row, then something
+typically requiring 4 byte alignment, and then an odd C<bool> later on.
+(C<bool>s are typically defined as C<char>s). So it would be good for someone
+to review the ordering of the variables, to see how much alignment padding can
+be removed.
+
+It's also worth checking that all variables are actually used. Perl 5.8.0
+shipped with C<PL_nrs> still defined in F<thrdvar.h>, despite it being unused
+since a change over a year earlier. Had this been spotted before release, it
+could have been removed, but now it has to remain in the 5.8.x releases to
+keep the structure the same size, to retain binary compatibility.
+
+It's probably worth checking if all need to be the types they are. For example
+
+ PERLVAR(Ierror_count, I32) /* how many errors so far, max 10 */
+
+might work as well if stored in a signed (or unsigned) 8 bit value, if the
+comment is accurate. C<PL_multi_open> and C<PL_multi_close> can probably
+become C<char>s. Finding variables to downsize coupled with rearrangement
+could shrink the interpreter structure; a size saving which is multiplied by
+the number of threads running.
+
+=head2 Profile Perl - am I hot or not?
+
+The Perl source code is stable enough that it makes sense to profile it,
+identify and optimise the hotspots. It would be good to measure the
+performance of the Perl interpreter using free tools such as cachegrind,
+gprof, and dtrace, and work to reduce the bottlenecks they reveal.
+
+As part of this, the idea of F<pp_hot.c> is that it contains the I<hot> ops,
+the ops that are most commonly used. The idea is that by grouping them, their
+object code will be adjacent in the executable, so they have a greater chance
+of already being in the CPU cache (or swapped in) due to being near another op
+already in use.
+
+Except that it's not clear if these really are the most commonly used ops. So
+as part of exercising your skills with coverage and profiling tools you might
+want to determine what ops I<really> are the most commonly used. And in turn
+suggest evictions and promotions to achieve a better F<pp_hot.c>.
+
+=head2 Allocate OPs from arenas
+
+Currently all new OP structures are individually malloc()ed and free()d.
+All C<malloc> implementations have space overheads, and are now as fast as
+custom allocates so it would both use less memory and less CPU to allocate
+the various OP structures from arenas. The SV arena code can probably be
+re-used for this.
+
+=head2 Improve win32/wince.c
+
+Currently, numerous functions look virtually, if not completely,
+identical in both C<win32/wince.c> and C<win32/win32.c> files, which can't
+be good.
+
+=head2 Use secure CRT functions when building with VC8 on Win32
+
+Visual C++ 2005 (VC++ 8.x) deprecated a number of CRT functions on the basis
+that they were "unsafe" and introduced differently named secure versions of
+them as replacements, e.g. instead of writing
+
+ FILE* f = fopen(__FILE__, "r");
+
+one should now write
+
+ FILE* f;
+ errno_t err = fopen_s(&f, __FILE__, "r");
+
+Currently, the warnings about these deprecations have been disabled by adding
+-D_CRT_SECURE_NO_DEPRECATE to the CFLAGS. It would be nice to remove that
+warning suppressant and actually make use of the new secure CRT functions.
+
+There is also a similar issue with POSIX CRT function names like fileno having
+been deprecated in favour of ISO C++ conformant names like _fileno. These
+warnings are also currently suppressed with the compiler option /wd4996. It
+might be nice to do as Microsoft suggest here too, although, unlike the secure
+functions issue, there is presumably little or no benefit in this case.
+
+=head1 Tasks that need a knowledge of XS
+
+These tasks would need C knowledge, and roughly the level of knowledge of
+the perl API that comes from writing modules that use XS to interface to
+C.
+
+=head2 shrink C<PVBM>s
+
+By removing unused elements and careful re-ordering, the structures for C<AV>s,
+C<HV>s, C<CV>s and C<GV>s have recently been shrunk considerably. C<PVIO>s
+probably aren't worth it, as typical programs don't use more than 8, and
+(at least) C<Filter::Util::Call> uses C<SvPVX>/C<SvCUR>/C<SvLEN> on a C<PVIO>,
+so it would mean code changes to modules on CPAN. C<PVBM>s might have some
+savings to win.
=head2 autovivification
Make all autovivification consistent w.r.t LVALUE/RVALUE and strict/no strict;
-=head2 fix tainting bugs
+This task is incremental - even a little bit of work on it will help.
-Fix the bugs revealed by running the test suite with the C<-t> switch (via
-C<make test.taintwarn>).
+=head2 Unicode in Filenames
+
+chdir, chmod, chown, chroot, exec, glob, link, lstat, mkdir, open,
+opendir, qx, readdir, readlink, rename, rmdir, stat, symlink, sysopen,
+system, truncate, unlink, utime, -X. All these could potentially accept
+Unicode filenames either as input or output (and in the case of system
+and qx Unicode in general, as input or output to/from the shell).
+Whether a filesystem - an operating system pair understands Unicode in
+filenames varies.
+
+Known combinations that have some level of understanding include
+Microsoft NTFS, Apple HFS+ (In Mac OS 9 and X) and Apple UFS (in Mac
+OS X), NFS v4 is rumored to be Unicode, and of course Plan 9. How to
+create Unicode filenames, what forms of Unicode are accepted and used
+(UCS-2, UTF-16, UTF-8), what (if any) is the normalization form used,
+and so on, varies. Finding the right level of interfacing to Perl
+requires some thought. Remember that an OS does not implicate a
+filesystem.
+
+(The Windows -C command flag "wide API support" has been at least
+temporarily retired in 5.8.1, and the -C has been repurposed, see
+L<perlrun>.)
+
+=head2 Unicode in %ENV
+
+Currently the %ENV entries are always byte strings.
+
+=head2 use less 'memory'
+
+Investigate trade offs to switch out perl's choices on memory usage.
+Particularly perl should be able to give memory back.
+
+This task is incremental - even a little bit of work on it will help.
+
+=head2 Re-implement C<:unique> in a way that is actually thread-safe
+
+The old implementation made bad assumptions on several levels. A good 90%
+solution might be just to make C<:unique> work to share the string buffer
+of SvPVs. That way large constant strings can be shared between ithreads,
+such as the configuration information in F<Config>.
=head2 Make tainting consistent
-Tainting would be easier to use if it didn't take documented shortcuts and allow
-taint to "leak" everywhere within an expression.
+Tainting would be easier to use if it didn't take documented shortcuts and
+allow taint to "leak" everywhere within an expression.
-=head2 Dual life everything
+=head2 readpipe(LIST)
-As part of the "dists" plan, anything that doesn't belong in the smallest perl
-distribution needs to be dual lifed. Anything else can be too.
+system() accepts a LIST syntax (and a PROGRAM LIST syntax) to avoid
+running a shell. readpipe() (the function behind qx//) could be similarly
+extended.
-=head1 Vague things
+=head2 strcat(), strcpy(), strncat(), strncpy(), sprintf(), vsprintf()
-Some more nebulous ideas
+Maybe create a utility that checks after each libperl.a creation that
+none of the above (nor sprintf(), vsprintf(), or *SHUDDER* gets())
+ever creep back to libperl.a.
-=head2 threads
+ nm libperl.a | ./miniperl -alne '$o = $F[0] if /:$/; print "$o $F[1]" if $F[0] eq "U" && $F[1] =~ /^(?:strn?c(?:at|py)|v?sprintf|gets)$/'
-Make threads more robust.
+Note, of course, that this will only tell whether B<your> platform
+is using those naughty interfaces.
-=head2 POSIX memory footprint
+=head2 Audit the code for destruction ordering assumptions
-Ilya observed that use POSIX; eats memory like there's no tomorrow, and at
-various times worked to cut it down. There is probably still fat to cut out -
-for example POSIX passes Exporter some very memory hungry data structures.
+Change 25773 notes
-=head2 Optimize away @_
+ /* Need to check SvMAGICAL, as during global destruction it may be that
+ AvARYLEN(av) has been freed before av, and hence the SvANY() pointer
+ is now part of the linked list of SV heads, rather than pointing to
+ the original body. */
+ /* FIXME - audit the code for other bugs like this one. */
-The old perltodo notes "Look at the "reification" code in C<av.c>".
+adding the C<SvMAGICAL> check to
+
+ if (AvARYLEN(av) && SvMAGICAL(AvARYLEN(av))) {
+ MAGIC *mg = mg_find (AvARYLEN(av), PERL_MAGIC_arylen);
-=head2 switch ops
+Go through the core and look for similar assumptions that SVs have particular
+types, as all bets are off during global destruction.
-The old perltodo notes "Although we have C<Switch.pm> in core, Larry points to
-the dormant C<nswitch> and C<cswitch> ops in F<pp.c>; using these opcodes would
-be much faster."
+=head2 Extend PerlIO and PerlIO::Scalar
+
+PerlIO::Scalar doesn't know how to truncate(). Implementing this
+would require extending the PerlIO vtable.
+
+Similarly the PerlIO vtable doesn't know about formats (write()), or
+about stat(), or chmod()/chown(), utime(), or flock().
+
+(For PerlIO::Scalar it's hard to see what e.g. mode bits or ownership
+would mean.)
+
+PerlIO doesn't do directories or symlinks, either: mkdir(), rmdir(),
+opendir(), closedir(), seekdir(), rewinddir(), glob(); symlink(),
+readlink().
+
+=head1 Tasks that need a knowledge of the interpreter
+
+These tasks would need C knowledge, and knowledge of how the interpreter works,
+or a willingness to learn.
+
+=head2 Implement $value ~~ 0 .. $range
+
+It would be nice to extend the syntax of the C<~~> operator to also
+understand numeric (and maybe alphanumeric) ranges.
=head2 Attach/detach debugger from running program
The old perltodo notes "With C<gdb>, you can attach the debugger to a running
program if you pass the process ID. It would be good to do this with the Perl
-debugger on a running Perl program, although I'm not sure how it would be done."
-ssh and screen do this with named pipes in tmp. Maybe we can too.
+debugger on a running Perl program, although I'm not sure how it would be
+done." ssh and screen do this with named pipes in /tmp. Maybe we can too.
-=head2 A decent benchmark
+=head2 LVALUE functions for lists
-perlbench seems impervious to any recent changes made to the perl core. It would
-be useful to have a reasonable general benchmarking suite that roughly
-represented what current perl programs do, and measurably reported whether
-tweaks to the core improve, degrade or don't really affect performance, to
-guide people attempting to optimise the guts of perl.
+The old perltodo notes that lvalue functions don't work for list or hash
+slices. This would be good to fix.
-=head2 readpipe(LIST)
+=head2 LVALUE functions in the debugger
-system() accepts a LIST syntax (and a PROGRAM LIST syntax) to avoid
-running a shell. readpipe() (the function behind qx//) could be similarly
-extended.
+The old perltodo notes that lvalue functions don't work in the debugger. This
+would be good to fix.
+
+=head2 regexp optimiser optional
+
+The regexp optimiser is not optional. It should configurable to be, to allow
+its performance to be measured, and its bugs to be easily demonstrated.
+
+=head2 delete &function
+
+Allow to delete functions. One can already undef them, but they're still
+in the stash.
+
+=head2 optional optimizer
+
+Make the peephole optimizer optional. Currently it performs two tasks as
+it walks the optree - genuine peephole optimisations, and necessary fixups of
+ops. It would be good to find an efficient way to switch out the
+optimisations whilst keeping the fixups.
+
+=head2 You WANT *how* many
+
+Currently contexts are void, scalar and list. split has a special mechanism in
+place to pass in the number of return values wanted. It would be useful to
+have a general mechanism for this, backwards compatible and little speed hit.
+This would allow proposals such as short circuiting sort to be implemented
+as a module on CPAN.
+
+=head2 lexical aliases
+
+Allow lexical aliases (maybe via the syntax C<my \$alias = \$foo>.
+
+=head2 entersub XS vs Perl
+
+At the moment pp_entersub is huge, and has code to deal with entering both
+perl and XS subroutines. Subroutine implementations rarely change between
+perl and XS at run time, so investigate using 2 ops to enter subs (one for
+XS, one for perl) and swap between if a sub is redefined.
=head2 Self ties
self ties are currently illegal because they caused too many segfaults. Maybe
the causes of these could be tracked down and self-ties on all types re-
instated.
+
+=head2 Optimize away @_
+
+The old perltodo notes "Look at the "reification" code in C<av.c>".
+
+=head2 What hooks would assertions need?
+
+Assertions are in the core, and work. However, assertions needed to be added
+as a core patch, rather than an XS module in ext, or a CPAN module, because
+the core has no hooks in the necessary places. It would be useful to
+investigate what hooks would need to be added to make it possible to provide
+the full assertion support from a CPAN module, so that we aren't constraining
+the imagination of future CPAN authors.
+
+=head2 Properly Unicode safe tokeniser and pads.
+
+The tokeniser isn't actually very UTF-8 clean. C<use utf8;> is a hack -
+variable names are stored in stashes as raw bytes, without the utf-8 flag
+set. The pad API only takes a C<char *> pointer, so that's all bytes too. The
+tokeniser ignores the UTF-8-ness of C<PL_rsfp>, or any SVs returned from
+source filters. All this could be fixed.
+
+=head1 Big projects
+
+Tasks that will get your name mentioned in the description of the "Highlights
+of 5.10"
+
+=head2 make ithreads more robust
+
+Generally make ithreads more robust. See also L</iCOW>
+
+This task is incremental - even a little bit of work on it will help, and
+will be greatly appreciated.
+
+One bit would be to write the missing code in sv.c:Perl_dirp_dup.
+
+=head2 iCOW
+
+Sarathy and Arthur have a proposal for an improved Copy On Write which
+specifically will be able to COW new ithreads. If this can be implemented
+it would be a good thing.
+
+=head2 (?{...}) closures in regexps
+
+Fix (or rewrite) the implementation of the C</(?{...})/> closures.
+
+=head2 A re-entrant regexp engine
+
+This will allow the use of a regex from inside (?{ }), (??{ }) and
+(?(?{ })|) constructs.
+
+=head2 Add class set operations to regexp engine
+
+Apparently these are quite useful. Anyway, Jeffery Friedl wants them.
+
+demerphq has this on his todo list, but right at the bottom.
+
+
projects / p5sagit/p5-mst-13.2.git / blobdiff