PERLTODO(1) Perl Programmers Reference Guide PERLTODO(1)NAMEperltodo - Perl TO-DO List
DESCRIPTION
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 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/
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 AUTHORS file, which ships in the official distribution. How many
other programming languages offer you 1 line of immortality?
Tasks that only need Perl knowledge
Remove duplication of test setup.
Schwern notes, that there's duplication of code - lots and lots of
tests have some variation on the big block of $Is_Foo checks. We can
safely put this into a file, change it to build an %Is hash and require
it. Maybe just put it into test.pl. Throw in the handy tainting
subroutines.
merge common code in installperl and installman
There are some common subroutines and a common "BEGIN" block in
installperl and installman. These should probably be merged. It would
also be good to check for duplication in all the utility scripts
supplied in the source tarball. It might be good to move them all to a
subdirectory, but this would require careful checking to find all
places that call them, and change those correctly.
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.
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 as simple as it sounds, particularly
with the flexibility POD allows for "=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 "make HTML install work", as the layout
of installation tree is needed to improve the cross-linking.
The addition of "Pod::Simple" and its related modules may make this
task easier to complete.
merge checkpods and podchecker
pod/checkpods.PL (and "make check" in the pod/ subdirectory) implements
a very basic check for pod files, but the errors it discovers aren't
found by podchecker. Add this check to podchecker, get rid of checkpods
and have "make check" use podchecker.
perlmodlib.PL rewrite
Currently perlmodlib.PL needs to be run from a source directory where
perl has been built, or some modules won't be found, and others will be
skipped. Make it run from a clean perl source tree (so it's
reproducible).
Parallel testing
(This probably impacts much more than the core: also the Test::Harness
and TAP::* modules on CPAN.)
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 option of running sets of tests in parallel. This would be
useful for tests in t/op/*.t and t/uni/*.t and maybe some sets of tests
in lib/.
Questions to answer
1. How does screen layout work when you're running more than one test?
2. How does the caller of test specify how many tests to run in
parallel?
3. How do setup/teardown tests identify themselves?
Pugs already does parallel testing - can their approach be re-used?
Make Schwern poorer
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.
Improve the coverage of the core tests
Use Devel::Cover to ascertain the core modules's test coverage, then
add tests that are currently missing.
test B
A full test suite for the B module would be nice.
Deparse inlined constants
Code such as this
use constant PI => 4;
warn PI
will currently deparse as
use constant ('PI', 4);
warn 4;
because the tokenizer inlines the value of the constant subroutine
"PI". This allows various compile time optimisations, such as constant
folding and dead code elimination. Where these haven't happened (such
as the example above) it ought be possible to make B::Deparse work out
the name of the original constant, because just enough information
survives in the symbol table to do this. Specifically, the same scalar
is used for the constant in the optree as is used for the constant
subroutine, so by iterating over all symbol tables and generating a
mapping of SV address to constant name, it would be possible to provide
B::Deparse with this functionality.
A decent benchmark
"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.
fix tainting bugs
Fix the bugs revealed by running the test suite with the "-t" switch
(via "make test.taintwarn").
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.
To make a minimal perl distribution, it's useful to look at
t/lib/commonsense.t.
Improving "threads::shared"
Investigate whether "threads::shared" could share aggregates properly
with only Perl level changes to shared.pm
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.
embed.pl/makedef.pl
There is a script 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". Functions are declared in
embed.fnc, variables in interpvar.h. Quite a few of the functions and
variables are conditionally declared there, using "#ifdef". However,
embed.pl doesn't understand the C macros, so the rules about which
symbols are present when is duplicated in makedef.pl. Writing things
twice is bad, m'kay. It would be good to teach "embed.pl" to
understand the conditional compilation, and hence remove the
duplication, and the mistakes it has caused.
use strict; and AutoLoad
Currently if you write
package Whack;
use AutoLoader 'AUTOLOAD';
use strict;
1;
__END__
sub bloop {
print join (' ', No, strict, here), "!\n";
}
then "use strict;" isn't in force within the autoloaded subroutines. It
would be more consistent (and less surprising) to arrange for all
lexical pragmas in force at the __END__ block to be in force within
each autoloaded subroutine.
There's a similar problem with SelfLoader.
Tasks that need a little sysadmin-type knowledge
Or if you prefer, tasks that you would learn from, and broaden your
skills base...
make HTML install work
There is an "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
1. Checking that cross linking between various parts of the
documentation works. In particular that links work between the
modules (files with POD in lib/) and the core documentation (files
in pod/)
2. Work out how to split "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 "-X", groups such as "getpwnam" to "endservent", two or more
"=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
"select")
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
installman script to compress as necessary.
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
· do a normal "Configure", but include Devel::Cover as a module to
install (see INSTALL for how to do this)
·
make perl
·
cd t; HARNESS_PERL_SWITCHES=-MDevel::Cover ./perl -I../lib harness
· Process the resulting Devel::Cover database
This just give you the coverage of the .pms. To also get the C level
coverage you need to
· Additionally tell "Configure" to use the appropriate C compiler
flags for "gcov"
·
make perl.gcov
(instead of "make perl")
· After running the tests run "gcov" to generate all the .gcov files.
(Including down in the subdirectories of ext/
· (From the top level perl directory) run "gcov2perl" on all the
".gcov" files to get their stats into the cover_db directory.
· Then process the Devel::Cover database
It would be good to add a single switch to "Configure" to specify that
you wanted to perform perl level coverage, and another to specify C
level coverage, and have "Configure" and the Makefile do all the right
things automatically.
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 %Config, so in this
situation %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 "Config.pm" about the installation
setup, possibly involving probing at install time or later, so that the
%Config in a binary distribution better describes the installed
machine, when the installed machine differs from the build machine in
some significant way.
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 makedef.pl to
support this format, and to provide a means within "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.
Cross-compile support
Currently "Configure" understands "-Dusecrosscompile" option. This
option arranges for building "miniperl" for TARGET machine, so this
"miniperl" is assumed then to be copied to TARGET machine and used as a
replacement of full "perl" executable.
This could be done little differently. Namely "miniperl" should be
built for HOST and then full "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. Tools
like MakeMaker will be mightily confused. Having around two different
types of executables and libraries (HOST and TARGET) makes life
interesting for Makefiles and shell (and Perl) scripts. There is
$Config{run}, normally empty, which can be used as an execution
wrapper. Also note that in some cross-compilation/execution
environments the HOST and the TARGET do not see the same filesystem(s),
the $Config{run} may need to do some file/directory copying back and
forth.
roffitall
Make pod/roffitall be updated by pod/buildtoc.
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
Exterminate PL_na!
"PL_na" festers still in the darkest corners of various typemap files.
It needs to be exterminated, replaced by a local variable of type
"STRLEN".
Modernize the order of directories in @INC
The way @INC is laid out by default, one cannot upgrade core (dual-
life) modules without overwriting files. This causes problems for
binary package builders. One possible proposal is laid out in this
message:
<http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/2002-04/msg02380.html>.
-Duse32bit*
Natively 64-bit systems need neither -Duse64bitint nor -Duse64bitall.
On these systems, it might be the default compilation mode, and there
is currently no guarantee that passing no use64bitall option to the
Configure process will build a 32bit perl. Implementing -Duse32bit*
options would be nice for perl 5.12.
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 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".
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 pp_hot.c is that it contains the 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 really are the most commonly
used. And in turn suggest evictions and promotions to achieve a better
pp_hot.c.
Allocate OPs from arenas
Currently all new OP structures are individually malloc()ed and
free()d. All "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.
Note that Configuring perl with "-Accflags=-DPL_OP_SLAB_ALLOC" will use
Perl_Slab_alloc() to pack optrees into a contiguous block, which is
probably superior to the use of OP arenas, esp. from a cache locality
standpoint. See "Profile Perl - am I hot or not?".
Improve win32/wince.c
Currently, numerous functions look virtually, if not completely,
identical in both "win32/wince.c" and "win32/win32.c" files, which
can't be good.
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 by adding
-D_CRT_NONSTDC_NO_DEPRECATE. 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.
strcat(), strcpy(), strncat(), strncpy(), sprintf(), vsprintf()
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.
nm libperl.a | ./miniperl -alne '$o = $F[0] if /:$/; print "$o $F[1]" if $F[0] eq "U" && $F[1] =~ /^(?:strn?c(?:at|py)|v?sprintf|gets)$/'
Note, of course, that this will only tell whether your platform is
using those naughty interfaces.
-D_FORTIFY_SOURCE=2, -fstack-protector
Recent glibcs support "-D_FORTIFY_SOURCE=2" and recent gcc (4.1
onwards?) supports "-fstack-protector", both of which give protection
against various kinds of buffer overflow problems. These should
probably be used for compiling Perl whenever available, Configure
and/or hints files should be adjusted to probe for the availability of
these features and enable them as appropriate.
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.
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.
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
perlrun.)
Most probably the right way to do this would be this: "Virtualize
operating system access".
Unicode in %ENV
Currently the %ENV entries are always byte strings. See "Virtualize
operating system access".
Unicode and glob()
Currently glob patterns and filenames returned from File::Glob::glob()
are always byte strings. See "Virtualize operating system access".
Unicode and lc/uc operators
Some built-in operators ("lc", "uc", etc.) behave differently, based on
what the internal encoding of their argument is. That should not be the
case. Maybe add a pragma to switch behaviour.
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.
Re-implement ":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 ":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 Config.
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.
readpipe(LIST)system() accepts a LIST syntax (and a PROGRAM LIST syntax) to avoid
running a shell. readpipe() (the function behind qx//) could be
similarly extended.
Audit the code for destruction ordering assumptions
Change 25773 notes
/* 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. */
adding the "SvMAGICAL" check to
if (AvARYLEN(av) && SvMAGICAL(AvARYLEN(av))) {
MAGIC *mg = mg_find (AvARYLEN(av), PERL_MAGIC_arylen);
Go through the core and look for similar assumptions that SVs have
particular types, as all bets are off during global destruction.
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().
See also "Virtualize operating system access".
-C on the #! line
It should be possible to make -C work correctly if found on the #!
line, given that all perl command line options are strict ASCII, and -C
changes only the interpretation of non-ASCII characters, and not for
the script file handle. To make it work needs some investigation of the
ordering of function calls during startup, and (by implication) a bit
of tweaking of that order.
Propagate const outwards from Perl_moreswitches()
Change 32057 changed the parameter and return value of
"Perl_moreswitches()" from <char *> to <const char *>. It should now be
possible to propagate const-correctness outwards to "S_parse_body()",
"Perl_moreswitches()" and "Perl_yylex()".
Duplicate logic in S_method_common() and Perl_gv_fetchmethod_autoload()
A comment in "S_method_common" notes
/* This code tries to figure out just what went wrong with
gv_fetchmethod. It therefore needs to duplicate a lot of
the internals of that function. We can't move it inside
Perl_gv_fetchmethod_autoload(), however, since that would
cause UNIVERSAL->can("NoSuchPackage::foo") to croak, and we
don't want that.
*/
If "Perl_gv_fetchmethod_autoload" gets rewritten to take (more) flag
bits, then it ought to be possible to move the logic from
"S_method_common" to the "right" place. When making this change it
would probably be good to also pass in at least the method name length,
if not also pre-computed hash values when known. (I'm contemplating a
plan to pre-compute hash values for common fixed strings such as "ISA"
and pass them in to functions.)
Organize error messages
Perl's diagnostics (error messages, see perldiag) could use
reorganizing and formalizing so that each error message has its stable-
for-all-eternity unique id, categorized by severity, type, and
subsystem. (The error messages would be listed in a datafile outside
of the Perl source code, and the source code would only refer to the
messages by the id.) This clean-up and regularizing should apply for
all croak() messages.
This would enable all sorts of things: easier translation/localization
of the messages (though please do keep in mind the caveats of
Locale::Maketext about too straightforward approaches to translation),
filtering by severity, and instead of grepping for a particular error
message one could look for a stable error id. (Of course, changing the
error messages by default would break all the existing software
depending on some particular error message...)
This kind of functionality is known as message catalogs. Look for
inspiration for example in the catgets() system, possibly even use it
if available-- but only if available, all platforms will not have
catgets().
For the really pure at heart, consider extending this item to cover
also the warning messages (see perllexwarn, "warnings.pl").
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.
UTF-8 revamp
The handling of Unicode is unclean in many places. For example, the
regexp engine matches in Unicode semantics whenever the string or the
pattern is flagged as UTF-8, but that should not be dependent on an
internal storage detail of the string. Likewise, case folding behaviour
is dependent on the UTF8 internal flag being on or off.
Properly Unicode safe tokeniser and pads.
The tokeniser isn't actually very UTF-8 clean. "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 "char *" pointer, so that's all
bytes too. The tokeniser ignores the UTF-8-ness of "PL_rsfp", or any
SVs returned from source filters. All this could be fixed.
state variable initialization in list context
Currently this is illegal:
state ($a, $b) = foo();
In Perl 6, "state ($a) = foo();" and "(state $a) = foo();" have
different semantics, which is tricky to implement in Perl 5 as
currently they produce the same opcode trees. The Perl 6 design is
firm, so it would be good to implement the necessary code in Perl 5.
There are comments in "Perl_newASSIGNOP()" that show the code paths
taken by various assignment constructions involving state variables.
Implement $value ~~ 0 .. $range
It would be nice to extend the syntax of the "~~" operator to also
understand numeric (and maybe alphanumeric) ranges.
A does() built-in
Like ref(), only useful. It would call the "DOES" method on objects; it
would also tell whether something can be dereferenced as an
array/hash/etc., or used as a regexp, etc.
<http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/2007-03/msg00481.html>
Tied filehandles and write() don't mix
There is no method on tied filehandles to allow them to be called back
by formats.
Attach/detach debugger from running program
The old perltodo notes "With "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.
Optimize away empty destructors
Defining an empty DESTROY method might be useful (notably in AUTOLOAD-
enabled classes), but it's still a bit expensive to call. That could
probably be optimized.
LVALUE functions for lists
The old perltodo notes that lvalue functions don't work for list or
hash slices. This would be good to fix.
LVALUE functions in the debugger
The old perltodo notes that lvalue functions don't work in the
debugger. This would be good to fix.
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.
delete &function
Allow to delete functions. One can already undef them, but they're
still in the stash.
"/w" regex modifier
That flag would enable to match whole words, and also to interpolate
arrays as alternations. With it, "/P/w" would be roughly equivalent to:
do { local $"='|'; /\b(?:P)\b/ }
See
<http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/2007-01/msg00400.html>
for the discussion.
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.
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.
lexical aliases
Allow lexical aliases (maybe via the syntax "my \$alias = \$foo".
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.
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 reinstated.
Optimize away @_
The old perltodo notes "Look at the "reification" code in "av.c"".
The yada yada yada operators
Perl 6's Synopsis 3 says:
The ... operator is the "yada, yada, yada" list operator, which is used
as the body in function prototypes. It complains bitterly (by calling
fail) if it is ever executed. Variant ??? calls warn, and !!! calls
die.
Those would be nice to add to Perl 5. That could be done without new
ops.
Virtualize operating system access
Implement a set of "vtables" that virtualizes operating system access
(open(), mkdir(), unlink(), readdir(), getenv(), etc.) At the very
least these interfaces should take SVs as "name" arguments instead of
bare char pointers; probably the most flexible and extensible way would
be for the Perl-facing interfaces to accept HVs. The system needs to
be per-operating-system and per-file-system hookable/filterable,
preferably both from XS and Perl level ("Files and Filesystems" in
perlport is good reading at this point, in fact, all of perlport is.)
This has actually already been implemented (but only for Win32), take a
look at iperlsys.h and win32/perlhost.h. While all Win32 variants go
through a set of "vtables" for operating system access, non-Win32
systems currently go straight for the POSIX/UNIX-style system/library
call. Similar system as for Win32 should be implemented for all
platforms. The existing Win32 implementation probably does not need to
survive alongside this proposed new implementation, the approaches
could be merged.
What would this give us? One often-asked-for feature this would enable
is using Unicode for filenames, and other "names" like %ENV, usernames,
hostnames, and so forth. (See "When Unicode Does Not Happen" in
perlunicode.)
But this kind of virtualization would also allow for things like
virtual filesystems, virtual networks, and "sandboxes" (though as long
as dynamic loading of random object code is allowed, not very safe
sandboxes since external code of course know not of Perl's vtables).
An example of a smaller "sandbox" is that this feature can be used to
implement per-thread working directories: Win32 already does this.
See also "Extend PerlIO and PerlIO::Scalar".
Investigate PADTMP hash pessimisation
The peephole optimier converts constants used for hash key lookups to
shared hash key scalars. Under ithreads, something is undoing this
work. See See
http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/2007-09/msg00793.html
Big projects
Tasks that will get your name mentioned in the description of the
"Highlights of 5.12"
make ithreads more robust
Generally make ithreads more robust. See also "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.
Fix Perl_sv_dup, et al so that threads can return objects.
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.
(?{...}) closures in regexps
Fix (or rewrite) the implementation of the "/(?{...})/" closures.
A re-entrant regexp engine
This will allow the use of a regex from inside (?{ }), (??{ }) and
(?(?{ })|) constructs.
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.
perl v5.10.0 2007-12-18 PERLTODO(1)
