perltodo
(1)
名称
perltodo - DO List
用法概要
Please see following description for synopsis
描述
Perl Programmers Reference Guide PERLTODO(1)
NAME
perltodo - Perl TO-DO List
DESCRIPTION
This is a list of wishes for Perl. The most up to date
version of this file is at
http://perl5.git.perl.org/perl.git/blob_plain/HEAD:/pod/perltodo.pod
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, and to learn from any previous
attempts. 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
Improve Porting/cmpVERSION.pl to work from git tags
See Porting/release_managers_guide.pod for a bit more
detail.
Migrate t/ from custom TAP generation
Many tests below t/ still generate TAP by "hand", rather
than using library functions. As explained in "Writing a
test" in perlhack, tests in t/ are written in a particular
way to test that more complex constructions actually work
before using them routinely. Hence they don't use
"Test::More", but instead there is an intentionally simpler
library, t/test.pl. However, quite a few tests in t/ have
not been refactored to use it. Refactoring any of these
tests, one at a time, is a useful thing TODO.
The subdirectories base, cmd and comp, that contain the most
basic tests, should be excluded from this task.
Test that regen.pl was run
There are various generated files shipped with the perl
distribution, for things like header files generate from
data. The generation scripts are written in perl, and all
can be run by regen.pl. However, because they're written in
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perl, we can't run them before we've built perl. We can't
run them as part of the Makefile, because changing files
underneath make confuses it completely, and we don't want to
run them automatically anyway, as they change files shipped
by the distribution, something we seek not do to.
If someone changes the data, but forgets to re-run regen.pl
then the generated files are out of sync. It would be good
to have a test in t/porting that checks that the generated
files are in sync, and fails otherwise, to alert someone
before they make a poor commit. I suspect that this would
require adapting the scripts run from regen.pl to have dry-
run options, and invoking them with these, or by refactoring
them into a library that does the generation, which can be
called by the scripts, and by the test.
Automate perldelta generation
The perldelta file accompanying each release summaries the
major changes. It's mostly manually generated currently,
but some of that could be automated with a bit of perl,
specifically the generation of
Modules and Pragmata
New Documentation
New Tests
See Porting/how_to_write_a_perldelta.pod for details.
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.
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.
Make ExtUtils::ParseXS use strict;
lib/ExtUtils/ParseXS.pm contains this line
# use strict; # One of these days...
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Simply uncomment it, and fix all the resulting issues :-)
The more practical approach, to break the task down into
manageable chunks, is to work your way though the code from
bottom to top, or if necessary adding extra "{ ... }"
blocks, and turning on strict within them.
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' test
coverage, then add tests that are currently missing.
test B
A full test suite for the B module would be nice.
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.
Move dual-life pod/*.PL into ext
Nearly all the dual-life modules have been moved to ext.
However, we still need to move pod/*.PL into their
respective directories in ext/. They're referenced by (at
least) "plextract" in Makefile.SH and "utils" in
win32/Makefile and win32/makefile.ml, and listed explicitly
in win32/pod.mak, vms/descrip_mms.template and utils.lst
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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.
profile installman
The installman script is slow. All it is doing text
processing, which we're told is something Perl is good at.
So it would be nice to know what it is doing that is taking
so much CPU, and where possible address it.
enable lexical enabling/disabling of inidvidual warnings
Currently, warnings can only be enabled or disabled by
category. There are times when it would be useful to quash a
single warning, not a whole category.
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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
o do a normal "Configure", but include Devel::Cover as a
module to install (see INSTALL for how to do this)
o
make perl
o
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cd t; HARNESS_PERL_SWITCHES=-MDevel::Cover ./perl -I../lib harness
o 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
o Additionally tell "Configure" to use the appropriate C
compiler flags for "gcov"
o
make perl.gcov
(instead of "make perl")
o After running the tests run "gcov" to generate all the
.gcov files. (Including down in the subdirectories of
ext/
o (From the top level perl directory) run "gcov2perl" on
all the ".gcov" files to get their stats into the
cover_db directory.
o 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
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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.
Split "linker" from "compiler"
Right now, Configure probes for two commands, and sets two
variables:
o "cc" (in cc.U)
This variable holds the name of a command to execute a C
compiler which can resolve multiple global references
that happen to have the same name. Usual values are cc
and gcc. Fervent ANSI compilers may be called c89. AIX
has xlc.
o "ld" (in dlsrc.U)
This variable indicates the program to be used to link
libraries for dynamic loading. On some systems, it is
ld. On ELF systems, it should be $cc. Mostly, we'll
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try to respect the hint file setting.
There is an implicit historical assumption from around
Perl5.000alpha something, that $cc is also the correct
command for linking object files together to make an
executable. This may be true on Unix, but it's not true on
other platforms, and there are a maze of work arounds in
other places (such as Makefile.SH) to cope with this.
Ideally, we should create a new variable to hold the name of
the executable linker program, probe for it in Configure,
and centralise all the special case logic there or in hints
files.
A small bikeshed issue remains - what to call it, given that
$ld is already taken (arguably for the wrong thing now, but
on SunOS 4.1 it is the command for creating dynamically-
loadable modules) and $link could be confused with the Unix
command line executable of the same name, which does
something completely different. Andy Dougherty makes the
counter argument "In parrot, I tried to call the command
used to link object files and libraries into an executable
link, since that's what my vaguely-remembered DOS and VMS
experience suggested. I don't think any real confusion has
ensued, so it's probably a reasonable name for perl5 to
use."
"Alas, I've always worried that introducing it would make
things worse, since now the module building utilities would
have to look for $Config{link} and institute a fall-back
plan if it weren't found." Although I can see that as
confusing, given that $Config{d_link} is true when (hard)
links are available.
Configure Windows using PowerShell
Currently, Windows uses hard-coded config files based to
build the config.h for compiling Perl. Makefiles are also
hard-coded and need to be hand edited prior to building
Perl. While this makes it easy to create a perl.exe that
works across multiple Windows versions, being able to
accurately configure a perl.exe for a specific Windows
versions and VS C++ would be a nice enhancement. With
PowerShell available on Windows XP and up, this may now be
possible. Step 1 might be to investigate whether this is
possible and use this to clean up our current makefile
situation. Step 2 would be to see if there would be a way
to use our existing metaconfig units to configure a Windows
Perl or whether we go in a separate direction and make it
so. Of course, we all know what step 3 is.
decouple -g and -DDEBUGGING
Currently Configure automatically adds "-DDEBUGGING" to the
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C compiler flags if it spots "-g" in the optimiser flags.
The pre-processor directive "DEBUGGING" enables perl's
command line "-D" options, but in the process makes perl
slower. It would be good to disentangle this logic, so that
C-level debugging with "-g" and Perl level debugging with
"-D" can easily be enabled independently.
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
Weed out needless PERL_UNUSED_ARG
The C code uses the macro "PERL_UNUSED_ARG" to stop
compilers warning about unused arguments. Often the
arguments can't be removed, as there is an external
constraint that determines the prototype of the function, so
this approach is valid. However, there are some cases where
"PERL_UNUSED_ARG" could be removed. Specifically
o The prototypes of (nearly all) static functions can be
changed
o Unused arguments generated by short cut macros are
wasteful - the short cut macro used can be changed.
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
<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.
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
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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.
One piece of Perl code that might make a good testbed is
installman.
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.
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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.
Fix POSIX::access() and chdir() on Win32
These functions currently take no account of DACLs and
therefore do not behave correctly in situations where access
is restricted by DACLs (as opposed to the read-only
attribute).
Furthermore, POSIX::access() behaves differently for
directories having the read-only attribute set depending on
what CRT library is being used. For example, the _access()
function in the VC6 and VC7 CRTs (wrongly) claim that such
directories are not writable, whereas in fact all
directories are writable unless access is denied by DACLs.
(In the case of directories, the read-only attribute
actually only means that the directory cannot be deleted.)
This CRT bug is fixed in the VC8 and VC9 CRTs (but, of
course, the directory may still not actually be writable if
access is indeed denied by DACLs).
For the chdir() issue, see ActiveState bug #74552:
http://bugs.activestate.com/show_bug.cgi?id=74552
Therefore, DACLs should be checked both for consistency
across CRTs and for the correct answer.
(Note that perl's -w operator should not be modified to
check DACLs. It has been written so that it reflects the
state of the read-only attribute, even for directories
(whatever CRT is being used), for symmetry with chmod().)
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
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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.
Arenas for GPs? For MAGIC?
"struct gp" and "struct magic" are both currently allocated
by "malloc". It might be a speed or memory saving to change
to using arenas. Or it might not. It would need some
suitable benchmarking first. In particular, "GP"s can
probably be changed with minimal compatibility impact
(probably nothing outside of the core, or even outside of
gv.c allocates them), but they probably aren't
allocated/deallocated often enough for a speed saving.
Whereas "MAGIC" is allocated/deallocated more often, but in
turn, is also something more externally visible, so changing
the rules here may bite external code.
Shared arenas
Several SV body structs are now the same size, notably PVMG
and PVGV, PVAV and PVHV, and PVCV and PVFM. It should be
possible to allocate and return same sized bodies from the
same actual arena, rather than maintaining one arena for
each. This could save 4-6K per thread, of memory no longer
tied up in the not-yet-allocated part of an arena.
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.
Write an XS cookbook
Create pod/perlxscookbook.pod with short, task-focused
'recipes' in XS that demonstrate common tasks and good
practices. (Some of these might be extracted from
perlguts.) The target audience should be XS novices, who
need more examples than perlguts but something less
overwhelming than perlapi. Recipes should provide "one
pretty good way to do it" instead of TIMTOWTDI.
Rather than focusing on interfacing Perl to C libraries,
such a cookbook should probably focus on how to optimize
Perl routines by re-writing them in XS. This will likely be
more motivating to those who mostly work in Perl but are
looking to take the next step into XS.
Deconstructing and explaining some simpler XS modules could
be one way to bootstrap a cookbook. (List::Util?
Class::XSAccessor? Tree::Ternary_XS?) Another option could
be deconstructing the implementation of some simpler
functions in op.c.
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Allow XSUBs to inline themselves as OPs
For a simple XSUB, often the subroutine dispatch takes more
time than the XSUB itself. The tokeniser already has the
ability to inline constant subroutines - it would be good to
provide a way to inline other subroutines.
Specifically, simplest approach looks to be to allow an XSUB
to provide an alternative implementation of itself as a
custom OP. A new flag bit in "CvFLAGS()" would signal to the
peephole optimiser to take an optree such as this:
b <@> leave[1 ref] vKP/REFC ->(end)
1 <0> enter ->2
2 <;> nextstate(main 1 -e:1) v:{ ->3
a <2> sassign vKS/2 ->b
8 <1> entersub[t2] sKS/TARG,1 ->9
- <1> ex-list sK ->8
3 <0> pushmark s ->4
4 <$> const(IV 1) sM ->5
6 <1> rv2av[t1] lKM/1 ->7
5 <$> gv(*a) s ->6
- <1> ex-rv2cv sK ->-
7 <$> gv(*x) s/EARLYCV ->8
- <1> ex-rv2sv sKRM*/1 ->a
9 <$> gvsv(*b) s ->a
perform the symbol table lookup of "rv2cv" and "gv(*x)",
locate the pointer to the custom OP that provides the direct
implementation, and re- write the optree something like:
b <@> leave[1 ref] vKP/REFC ->(end)
1 <0> enter ->2
2 <;> nextstate(main 1 -e:1) v:{ ->3
a <2> sassign vKS/2 ->b
7 <1> custom_x -> 8
- <1> ex-list sK ->7
3 <0> pushmark s ->4
4 <$> const(IV 1) sM ->5
6 <1> rv2av[t1] lKM/1 ->7
5 <$> gv(*a) s ->6
- <1> ex-rv2cv sK ->-
- <$> ex-gv(*x) s/EARLYCV ->7
- <1> ex-rv2sv sKRM*/1 ->a
8 <$> gvsv(*b) s ->a
i.e. the gv(*) OP has been nulled and spliced out of the
execution path, and the "entersub" OP has been replaced by
the custom op.
This approach should provide a measurable speed up to simple
XSUBs inside tight loops. Initially one would have to write
the OP alternative implementation by hand, but it's likely
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that this should be reasonably straightforward for the type
of XSUB that would benefit the most. Longer term, once the
run-time implementation is proven, it should be possible to
progressively update ExtUtils::ParseXS to generate OP
implementations for some XSUBs.
Remove the use of SVs as temporaries in dump.c
dump.c contains debugging routines to dump out the contains
of perl data structures, such as "SV"s, "AV"s and "HV"s.
Currently, the dumping code uses "SV"s for its temporary
buffers, which was a logical initial implementation choice,
as they provide ready made memory handling.
However, they also lead to a lot of confusion when it
happens that what you're trying to debug is seen by the code
in dump.c, correctly or incorrectly, as a temporary scalar
it can use for a temporary buffer. It's also not possible to
dump scalars before the interpreter is properly set up, such
as during ithreads cloning. It would be good to
progressively replace the use of scalars as string
accumulation buffers with something much simpler, directly
allocated by "malloc". The dump.c code is (or should be)
only producing 7 bit US-ASCII, so output character sets are
not an issue.
Producing and proving an internal simple buffer allocation
would make it easier to re-write the internals of the PerlIO
subsystem to avoid using "SV"s for its buffers, use of which
can cause problems similar to those of dump.c, at similar
times.
safely supporting POSIX SA_SIGINFO
Some years ago Jarkko supplied patches to provide support
for the POSIX SA_SIGINFO feature in Perl, passing the extra
data to the Perl signal handler.
Unfortunately, it only works with "unsafe" signals, because
under safe signals, by the time Perl gets to run the signal
handler, the extra information has been lost. Moreover, it's
not easy to store it somewhere, as you can't call mutexs, or
do anything else fancy, from inside a signal handler.
So it strikes me that we could provide safe SA_SIGINFO
support
1. Provide global variables for two file descriptors
2. When the first request is made via "sigaction" for
"SA_SIGINFO", create a pipe, store the reader in one,
the writer in the other
3. In the "safe" signal handler
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("Perl_csighandler()"/"S_raise_signal()"), if the
"siginfo_t" pointer non-"NULL", and the writer file
handle is open,
1. serialise signal number, "struct siginfo_t" (or
at least the parts we care about) into a small
auto char buff
2. "write()" that (non-blocking) to the writer fd
1. if it writes 100%, flag the signal
in a counter of "signals on the
pipe" akin to the current per-
signal-number counts
2. if it writes 0%, assume the pipe is
full. Flag the data as lost?
3. if it writes partially, croak a
panic, as your OS is broken.
4. in the regular "PERL_ASYNC_CHECK()" processing, if there
are "signals on the pipe", read the data out,
deserialise, build the Perl structures on the stack
(code in "Perl_sighandler()", the "unsafe" handler), and
call as usual.
I think that this gets us decent "SA_SIGINFO" support,
without the current risk of running Perl code inside the
signal handler context. (With all the dangers of things like
"malloc" corruption that that currently offers us)
For more information see the thread starting with this
message:
http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/2008-03/msg00305.html
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.
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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".
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.
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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.
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()
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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.
forbid labels with keyword names
Currently "goto keyword" "computes" the label value:
$ perl -e 'goto print'
Can't find label 1 at -e line 1.
It is controversial if the right way to avoid the confusion
is to forbid labels with keyword names, or if it would be
better to always treat bareword expressions after a "goto"
as a label and never as a keyword.
truncate() prototype
The prototype of truncate() is currently $$. It should
probably be "*$" instead. (This is changed in opcode.pl)
decapsulation of smart match argument
Currently "$foo ~~ $object" will die with the message "Smart
matching a non-overloaded object breaks encapsulation". It
would be nice to allow to bypass this by using explictly the
syntax "$foo ~~ %$object" or "$foo ~~ @$object".
error reporting of [$a ; $b]
Using ";" inside brackets is a syntax error, and we don't
propose to change that by giving it any meaning. However,
it's not reported very helpfully:
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$ perl -e '$a = [$b; $c];'
syntax error at -e line 1, near "$b;"
syntax error at -e line 1, near "$c]"
Execution of -e aborted due to compilation errors.
It should be possible to hook into the tokeniser or the
lexer, so that when a ";" is parsed where it is not legal as
a statement terminator (ie inside "{}" used as a hashref,
"[]" or "()") it issues an error something like ';' isn't
legal inside an expression - if you need multiple statements
use a do {...} block. See the thread starting at
http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/2008-09/msg00573.html
lexicals used only once
This warns:
$ perl -we '$pie = 42'
Name "main::pie" used only once: possible typo at -e line 1.
This does not:
$ perl -we 'my $pie = 42'
Logically all lexicals used only once should warn, if the
user asks for warnings. An unworked RT ticket (#5087) has
been open for almost seven years for this discrepancy.
UTF-8 revamp
The handling of Unicode is unclean in many places. For
example, the regexp engine matches in Unicode semantics
whenever the string or the pattern is flagged as UTF-8, but
that should not be dependent on an internal storage detail
of the string.
Properly Unicode safe tokeniser and pads.
The tokeniser isn't actually very UTF-8 clean. "use utf8;"
is a hack - variable names are stored in stashes as raw
bytes, without the utf-8 flag set. The pad API only takes a
"char *" pointer, so that's all bytes too. The tokeniser
ignores the UTF-8-ness of "PL_rsfp", or any SVs returned
from source filters. All this could be fixed.
state variable initialization in list context
Currently this is illegal:
state ($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
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"Perl_newASSIGNOP()" that show the code paths taken by
various assignment constructions involving state variables.
Implement $value ~~ 0 .. $range
It would be nice to extend the syntax of the "~~" operator
to also understand numeric (and maybe alphanumeric) ranges.
A does() built-in
Like ref(), only useful. It would call the "DOES" method on
objects; it would also tell whether something can be
dereferenced as an array/hash/etc., or used as a regexp,
etc.
http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/2007-03/msg00481.html
<http://www.xray.mpe.mpg.de/mailing-
lists/perl5-porters/2007-03/msg00481.html>
Tied filehandles and write() don't mix
There is no method on tied filehandles to allow them to be
called back by formats.
Propagate compilation hints to the debugger
Currently a debugger started with -dE on the command-line
doesn't see the features enabled by -E. More generally hints
($^H and "%^H") aren't propagated to the debugger. Probably
it would be a good thing to propagate hints from the
innermost non-"DB::" scope: this would make code eval'ed in
the debugger see the features (and strictures, etc.)
currently in scope.
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.
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.
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.
"/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:
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do { local $"='|'; /\b(?:P)\b/ }
See
http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/2007-01/msg00400.html
<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"".
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
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("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 optimiser converts constants used for hash key
lookups to shared hash key scalars. Under ithreads,
something is undoing this work. See
http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/2007-09/msg00793.html
Store the current pad in the OP slab allocator
Currently we leak ops in various cases of parse failure. I
suggested that we could solve this by always using the op
slab allocator, and walking it to free ops. Dave comments
that as some ops are already freed during optree creation
one would have to mark which ops are freed, and not double
free them when walking the slab. He notes that one problem
with this is that for some ops you have to know which pad
was current at the time of allocation, which does change. I
suggested storing a pointer to the current pad in the memory
allocated for the slab, and swapping to a new slab each time
the pad changes. Dave thinks that this would work.
repack the optree
Repacking the optree after execution order is determined
could allow removal of NULL ops, and optimal ordering of OPs
with respect to cache-line filling. The slab allocator
could be reused for this purpose. I think that the best way
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to do this is to make it an optional step just before the
completed optree is attached to anything else, and to use
the slab allocator unchanged, so that freeing ops is
identical whether or not this step runs. Note that the slab
allocator allocates ops downwards in memory, so one would
have to actually "allocate" the ops in reverse-execution
order to get them contiguous in memory in execution order.
See
http://www.nntp.perl.org/group/perl.perl5.porters/2007/12/msg131975.html
Note that running this copy, and then freeing all the old
location ops would cause their slabs to be freed, which
would eliminate possible memory wastage if the previous
suggestion is implemented, and we swap slabs more
frequently.
eliminate incorrect line numbers in warnings
This code
use warnings;
my $undef;
if ($undef == 3) {
} elsif ($undef == 0) {
}
used to produce this output:
Use of uninitialized value in numeric eq (==) at wrong.pl line 4.
Use of uninitialized value in numeric eq (==) at wrong.pl line 4.
where the line of the second warning was misreported - it
should be line 5. Rafael fixed this - the problem arose
because there was no nextstate OP between the execution of
the "if" and the "elsif", hence "PL_curcop" still reports
that the currently executing line is line 4. The solution
was to inject a nextstate OPs for each "elsif", although it
turned out that the nextstate OP needed to be a nulled OP,
rather than a live nextstate OP, else other line numbers
became misreported. (Jenga!)
The problem is more general than "elsif" (although the
"elsif" case is the most common and the most confusing).
Ideally this code
use warnings;
my $undef;
my $a = $undef + 1;
my $b
= $undef
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+ 1;
would produce this output
Use of uninitialized value $undef in addition (+) at wrong.pl line 4.
Use of uninitialized value $undef in addition (+) at wrong.pl line 7.
(rather than lines 4 and 5), but this would seem to require
every OP to carry (at least) line number information.
What might work is to have an optional line number in memory
just before the BASEOP structure, with a flag bit in the op
to say whether it's present. Initially during compile every
OP would carry its line number. Then add a late pass to the
optimiser (potentially combined with "repack the optree")
which looks at the two ops on every edge of the graph of the
execution path. If the line number changes, flags the
destination OP with this information. Once all paths are
traced, replace every op with the flag with a nextstate-
light op (that just updates "PL_curcop"), which in turn then
passes control on to the true op. All ops would then be
replaced by variants that do not store the line number.
(Which, logically, why it would work best in conjunction
with "repack the optree", as that is already
copying/reallocating all the OPs)
(Although I should note that we're not certain that doing
this for the general case is worth it)
optimize tail-calls
Tail-calls present an opportunity for broadly applicable
optimization; anywhere that "return foo(...)" is called, the
outer return can be replaced by a goto, and foo will return
directly to the outer caller, saving (conservatively) 25% of
perl's call&return cost, which is relatively higher than in
C. The scheme language is known to do this heavily.
B::Concise provides good insight into where this
optimization is possible, ie anywhere entersub,leavesub op-
sequence occurs.
perl -MO=Concise,-exec,a,b,-main -e 'sub a{ 1 }; sub b {a()}; b(2)'
Bottom line on this is probably a new pp_tailcall function
which combines the code in pp_entersub, pp_leavesub. This
should probably be done 1st in XS, and using B::Generate to
patch the new OP into the optrees.
Big projects
Tasks that will get your name mentioned in the description
of the "Highlights of 5.12"
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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.
Tasks for microperl
[ Each and every one of these may be obsolete, but they were
listed
in the old Todo.micro file]
make creating uconfig.sh automatic
make creating Makefile.micro automatic
do away with fork/exec/wait?
(system, popen should be enough?)
some of the uconfig.sh really needs to be probed (using cc) in
buildtime:
(uConfigure? :-) native datatype widths and endianness come
to mind
ATTRIBUTES
See attributes(5) for descriptions of the following
attributes:
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+---------------+------------------+
|ATTRIBUTE TYPE | ATTRIBUTE VALUE |
+---------------+------------------+
|Availability | runtime/perl-512 |
+---------------+------------------+
|Stability | Uncommitted |
+---------------+------------------+
NOTES
This software was built from source available at
https://java.net/projects/solaris-userland. The original
community source was downloaded from
http://www.cpan.org/src/5.0/perl-5.12.5.tar.bz2
Further information about this software can be found on the
open source community website at http://www.perl.org/.
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