X-Git-Url: http://git.shadowcat.co.uk/gitweb/gitweb.cgi?a=blobdiff_plain;f=pod%2Fperltodo.pod;h=7de53535c07c1bb47cc16c534b368bef46513e07;hb=af9e49b40a4cc2d6c0d5ebad7e84fb62143b24e1;hp=6698b8da971e9292e426b16572683087636bead2;hpb=0c13e809ed4d404a11e0397efa6d6cb6bbb30d3e;p=p5sagit%2Fp5-mst-13.2.git

diff --git a/pod/perltodo.pod b/pod/perltodo.pod
index 6698b8d..7de5353 100644
--- a/pod/perltodo.pod
+++ b/pod/perltodo.pod
@@ -4,66 +4,462 @@ perltodo - Perl TO-DO List
 
 =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 a 5.9.3 release
 
-=head1 (?{...}) closures in regexps
+=over
 
-Fix (or rewrite) the implementation of the C</(?{...})/> closures.
+=item *
+Implement L</lexical pragmas>
 
-=head1 pragmata
+=back
 
-=head2 lexical pragmas
+=head2 Needed for a 5.9.4 release
 
-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.
+=over
 
-=head2 use less 'memory'
+=item *
+Review assertions. Review syntax to combine assertions. Can assertions  take
+advantage of the lexical pragams work? L</What hooks would assertions need?>
 
-Investigate trade offs to switch out perl's choices on memory usage.
-Particularly perl should be able to give memory back.
+=back
 
-=head1 prototypes and functions
+=head2 Needed for a 5.9.5 release
 
-=head2 _ prototype character
+=over
 
-Study the possibility of adding a new prototype character, C<_>, meaning
-"this argument defaults to $_".
+=item *
+Implement L</_ prototype character>
 
-=head2 inlining autoloaded constants
+=item *
+Implement L</state variables>
 
-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.
+=back
+
+=head2 Needed for a 5.9.6 release
+
+Stabilisation. If all goes well, this will be the equivalent of a 5.10-beta.
+
+=head1 Tasks that only need Perl knowledge
+
+=head2 common test code for timed bail out
+
+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.
+
+=head2 POD -> HTML conversion in the core still sucks
+
+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.
+
+=head2 Parallel testing
+
+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/>.
+
+Questions to answer
+
+=over 4
+
+=item 1
+
+How does screen layout work when you're running more than one test?
+
+=item 2
+
+How does the caller of test specify how many tests to run in parallel?
+
+=item 3
+
+How do setup/teardown tests identify themselves?
+
+=back
+
+Pugs already does parallel testing - can their approach be re-used?
+
+=head2 Make Schwern poorer
+
+We should have 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.
+
+See F<t/lib/1_compile.t> for the 3 remaining modules that need tests.
+
+=head2 Improve the coverage of the core tests
+
+Use Devel::Cover to ascertain the core's test coverage, then add tests that
+are currently missing.
+
+=head2 test B
+
+A full test suite for the B module would be nice.
+
+=head2 A decent benchmark
+
+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 fix tainting bugs
+
+Fix the bugs revealed by running the test suite with the C<-t> switch (via
+C<make test.taintwarn>).
+
+=head2 Dual life everything
+
+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.
+
+=head2 Improving C<threads::shared>
+
+Investigate whether C<threads::shared> could share aggregates properly with
+only Perl level changes to shared.pm
+
+=head2 POSIX memory footprint
+
+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.
+
+
+
+
+
+
+
+=head1 Tasks that need a little sysadmin-type knowledge
+
+Or if you prefer, tasks that you would learn from, and broaden your skills
+base...
+
+=head2 Relocatable perl
+
+The C level patches needed to create a relocatable perl binary are done, as
+is the work on F<Config.pm>. All that's left to do is the C<Configure> tweaking
+to let people specify how they want to do the install.
+
+=head2 make HTML install work
+
+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
+
+=over 4
+
+=item 1
+
+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/>)
+
+=item 2
+
+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
+
+    =item substr EXPR,OFFSET,LENGTH,REPLACEMENT
+    
+    =item substr EXPR,OFFSET,LENGTH
+    
+    =item substr EXPR,OFFSET
+
+and different parameter lists having different meanings. (eg C<select>)
+
+=back
+
+=head2 compressed man pages
+
+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 Add a code coverage target to the Makefile
+
+Make it easy for anyone to run Devel::Cover on the core's tests. The steps
+to do this manually are roughly
+
+=over 4
+
+=item *
+
+do a normal C<Configure>, but include Devel::Cover as a module to install
+(see F<INSTALL> for how to do this)
+
+=item *
+
+    make perl
+
+=item *
+
+    cd t; HARNESS_PERL_SWITCHES=-MDevel::Cover ./perl -I../lib harness
+
+=item *
+
+Process the resulting Devel::Cover database
+
+=back
+
+This just give you the coverage of the F<.pm>s. To also get the C level
+coverage you need to
+
+=over 4
+
+=item *
+
+Additionally tell C<Configure> to use the appropriate C compiler flags for
+C<gcov>
+
+=item *
+
+    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 build 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 make parallel builds work
+
+Currently parallel builds (such as C<make -j3>) don't work reliably. We believe
+that this is due to incomplete dependency specification in the F<Makefile>.
+It would be good if someone were able to track down the causes of these
+problems, so that parallel builds worked properly.
+
+=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.
+
+
+
+
+=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 Make it clear from -v if this is the exact official release
+
+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.
+
+It would be useful to find an elegant way to have the "this is an interim
+maintenance release" or "this is a release candidate" in the terse -v output,
+and have it so that it's easy for the pumpking to remove this just as the
+release tarball is rolled up. This way the version pulled out of rsync would
+always say "I'm a development release" and it would be safe to bump the
+reported minor version as soon as a release ships, which would aid perl
+developers.
+
+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".
+
+=head2 Tidy up global variables
+
+There's a note in F<intrpvar.h>
+
+  /* These two variables are needed to preserve 5.8.x bincompat because
+     we can't change function prototypes of two exported functions.
+     Probably should be taken out of blead soon, and relevant prototypes
+     changed.  */
+
+So doing this, and removing any of the unused variables still present would
+be good.
+
+=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.
+
+=head2 bincompat functions
 
-=head2 Finish off lvalue functions
+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?
+
+=head2 am I hot or not?
+
+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
+anyone feeling like exercising their skill with coverage and profiling tools
+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 emulate the per-thread memory pool on Unix
+
+For Windows, ithreads allocates memory for each thread from a separate pool,
+which it discards at thread exit. It also checks that memory is free()d to
+the correct pool. Neither check is done on Unix, so code developed there won't
+be subject to such strictures, so can harbour bugs that only show up when the
+code reaches Windows.
+
+It would be good to be able to optionally emulate the Window pool system on
+Unix, to let developers who only have access to Unix, or want to use
+Unix-specific debugging tools, check for these problems. To do this would
+involve figuring out how the C<PerlMem_*> macros wrap C<malloc()> access, and
+providing a layer that records/checks the identity of the thread making the
+call, and recording all the memory allocated by each thread via this API so
+that it can be summarily free()d at thread exit. One implementation idea
+would be to increase the size of allocation, and store the C<my_perl> pointer
+(to identify the thread) at the start, along with pointers to make a linked
+list of blocks for this thread. To avoid alignment problems it would be
+necessary to do something like
+
+  union memory_header_padded {
+    struct memory_header {
+      void *thread_id;   /* For my_perl */
+      void *next;        /* Pointer to next block for this thread */
+    } data;
+    long double padding; /* whatever type has maximal alignment constraint */
+  };
+
+
+although C<long double> might not be the only type to add to the padding
+union.
 
-The old perltodo notes "They don't work in the debugger, and they don't work for
-list or hash slices."
+=head2 reduce duplication in sv_setsv_flags
 
-=head1 Unicode and UTF8
+C<Perl_sv_setsv_flags> has a comment
+C</* There's a lot of redundancy below but we're going for speed here */>
+
+Whilst this was true 10 years ago, the growing disparity between RAM and CPU
+speeds mean that the trade offs have changed. In addition, the duplicate code
+adds to the maintenance burden. It would be good to see how much of the
+redundancy can be pruned, particular in the less common paths. (Profiling
+tools at the ready...). For example, why does the test for
+"Can't redefine active sort subroutine" need to occur in two places?
+
+
+
+
+=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 IPv6
+
+Clean this up. Check everything in core works
+
+=head2 shrink C<GV>s, C<CV>s
+
+By removing unused elements and careful re-ordering, the structures for C<AV>s
+and C<HV>s have recently been shrunk considerably. It's probable that the same
+approach would find savings in C<GV>s and C<CV>s, if not all the other
+larger-than-C<PVMG> types.
+
+=head2 merge Perl_sv_2[inpu]v
+
+There's a lot of code shared between C<Perl_sv_2iv_flags>,
+C<Perl_sv_2uv_flags>, C<Perl_sv_2nv>, and C<Perl_sv_2pv_flags>. It would be
+interesting to see if some of it can be merged into common shared static
+functions. In particular, C<Perl_sv_2uv_flags> started out as a cut&paste
+from C<Perl_sv_2iv_flags> around 5.005_50 time, and it may be possible to
+replace both with a single function that returns a value or union which is
+split out by the macros in F<sv.h>
+
+=head2 UTF8 caching code
+
+The string position/offset cache is not optional. It should be.
 
 =head2 Implicit Latin 1 => Unicode translation
 
@@ -74,9 +470,13 @@ 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).
 
-=head2 UTF8 caching code
+This task is incremental - even a little bit of work on it will help.
 
-The string position/offset cache is not optional. It should be.
+=head2 autovivification
+
+Make all autovivification consistent w.r.t LVALUE/RVALUE and strict/no strict;
+
+This task is incremental - even a little bit of work on it will help.
 
 =head2 Unicode in Filenames
 
@@ -105,195 +505,188 @@ L<perlrun>.)
 
 Currently the %ENV entries are always byte strings.
 
-=head1 Regexps
-
-=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 common suffices/prefices in regexps (trie optimization)
-
-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.
+=head2 use less 'memory'
 
-=head1 POD
+Investigate trade offs to switch out perl's choices on memory usage.
+Particularly perl should be able to give memory back.
 
-=head2 POD -> HTML conversion still sucks
+This task is incremental - even a little bit of work on it will help.
 
-Which is crazy given just how simple POD purports to be, and how simple HTML
-can be.
+=head2 Re-implement C<:unique> in a way that is actually thread-safe
 
-=head1 Misc medium sized projects
+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 UNITCHECK
+=head2 Make tainting consistent
 
-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.
+Tainting would be easier to use if it didn't take documented shortcuts and
+allow taint to "leak" everywhere within an expression.
 
-=head2 optional optimizer
+=head2 readpipe(LIST)
 
-Make the peephole optimizer optional.
+system() accepts a LIST syntax (and a PROGRAM LIST syntax) to avoid
+running a shell. readpipe() (the function behind qx//) could be similarly
+extended.
 
-=head2 You WANT *how* many
 
-Currently contexts are void, scalar and list. sort 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 no 6
+=head1 Tasks that need a knowledge of the interpreter
 
-Make C<no 6> and C<no v6> work (opposite of C<use 5.005>, etc.).
+These tasks would need C knowledge, and knowledge of how the interpreter works,
+or a willingness to learn.
 
-=head2 IPv6
+=head2 lexical pragmas
 
-Clean this up. Check everything in core works
+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.
 
-=head2 entersub XS vs Perl
+=head2 Attach/detach debugger from running program
 
-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.
+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.
 
-=head2 @INC source filter to Filter::Simple
+=head2 inlining autoloaded constants
 
-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.
+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.
 
-=head2 bincompat functions
+=head2 Constant folding
 
-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?
+The peephole optimiser should trap errors during constant folding, and give
+up on the folding, rather than bailing out at compile time.  It is quite
+possible that the unfoldable constant is in unreachable code, eg something
+akin to C<$a = 0/0 if 0;>
 
-=head2 Use fchown/fchmod internally
+=head2 LVALUE functions for lists
 
-The old perltodo notes "This has been done in places, but needs a thorough
-code review. Also fchdir is available in some platforms."
+The old perltodo notes that lvalue functions don't work for list or hash
+slices. This would be good to fix.
 
-=head2 foreach reverse
+=head2 LVALUE functions in the debugger
 
-The old perltodo notes that we could optimise foreach to iterate in reverse.
-(instead of making a reversed copy on the stack)
+The old perltodo notes that lvalue functions don't work in the debugger. This
+would be good to fix.
 
-=head1 Tests
+=head2 _ prototype character
 
-=head2 Make Schwern poorer
+Study the possibility of adding a new prototype character, C<_>, meaning
+"this argument defaults to $_".
 
-Tests for everything, At which point Schwern coughs up $500 to TPF.
+=head2 state variables
 
-=head2 test B
+C<my $foo if 0;> is deprecated, and should be replaced with
+C<state $x = "initial value\n";> the syntax from Perl 6.
 
-A test suite for the B module would be nice.
+=head2 @INC source filter to Filter::Simple
 
-=head2 Improve tests for Config.pm
+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.
 
-Config.pm doesn't appear to be well tested.
+=head2 regexp optimiser optional
 
-=head2 common test code for timed bailout
+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.
 
-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.
+=head2 UNITCHECK
 
-=head1 Installation
+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.
 
-=head2 compressed man pages
+=head2 optional optimizer
 
-Be able to install them
+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 Make Config.pm cope with differences between build and installed perl
+=head2 You WANT *how* many
 
-=head2 Relocatable perl
+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.
 
-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?
+=head2 lexical aliases
 
-=head2 make HTML install work
+Allow lexical aliases (maybe via the syntax C<my \$alias = \$foo>.
 
-=head2 put patchlevel in -v
+=head2 entersub XS vs Perl
 
-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
-information can get lost in bugs reports. Because of this, the minor version
-isn't bumped up util RC time, to minimise the possibility of versions of perl
-escaping that believe themselves to be newer than they actually are.
+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.
 
-It would be useful to find an elegant way to have the "this is an interim
-maintenance release" or "this is a release candidate" in the terse -v output,
-and have it so that it's easy for the pumpking to remove this just as the
-release tarball is rolled up. This way the version pulled out of rsync would
-always say "I'm a development release" and it would be safe to bump the
-reported minor version as soon as a release ships, which would aid perl
-developers.
+=head2 Self ties
 
-=head1 Incremental things
+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.
 
-Some tasks that don't need to get done in one big hit.
+=head2 Optimize away @_
 
-=head2 autovivification
+The old perltodo notes "Look at the "reification" code in C<av.c>".
 
-Make all autovivification consistent w.r.t LVALUE/RVALUE and strict/no strict;
+=head2 switch ops
 
-=head2 fix tainting bugs
+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."
 
-Fix the bugs revealed by running the test suite with the C<-t> switch (via
-C<make test.taintwarn>).
+=head2 What hooks would assertions need?
 
-=head2 Make tainting consistent
+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.
 
-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
 
-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.
 
-=head1 Vague things
 
-Some more nebulous ideas
 
-=head2 threads
 
-Make threads more robust.
+=head1 Big projects
 
-=head2 POSIX memory footprint
+Tasks that will get your name mentioned in the description of the "Highlights
+of 5.10"
 
-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 make ithreads more robust
 
-=head2 Optimize away @_
+Generally make ithreads more robust. See also L</iCOW>
 
-The old perltodo notes "Look at the "reification" code in C<av.c>"
+This task is incremental - even a little bit of work on it will help, and
+will be greatly appreciated.
 
-=head2 switch ops
+=head2 iCOW
 
-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."
+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 Attach/detach debugger from running program
+=head2 (?{...}) closures in regexps
 
-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.
+Fix (or rewrite) the implementation of the C</(?{...})/> closures.
 
-=head2 A decent benchmark
+=head2 A re-entrant regexp engine
 
-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.
+This will allow the use of a regex from inside (?{ }), (??{ }) and
+(?(?{ })|) constructs.