X-Git-Url: http://git.shadowcat.co.uk/gitweb/gitweb.cgi?a=blobdiff_plain;f=pod%2Fperltodo.pod;h=7c7dc96e3ff286fa90f67225dd83019c7c5427f3;hb=e40b81a3dd247b1a29fc78399677b77b78b5f183;hp=a4e655cdcbba2b181e35d89989b877842e5ccdb6;hpb=46925299862a0e463c499a99799cb56d12e9b3a9;p=p5sagit%2Fp5-mst-13.2.git

diff --git a/pod/perltodo.pod b/pod/perltodo.pod
index a4e655c..7c7dc96 100644
--- a/pod/perltodo.pod
+++ b/pod/perltodo.pod
@@ -15,9 +15,20 @@ 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
+F<AUTHORS> file, which ships in the official distribution. How many other
+programming languages offer you 1 line of immortality?
 
+=head1 The roadmap to 5.10
 
+The roadmap to 5.10 envisages feature based releases, as various items in this
+TODO are completed.
 
+=head2 Needed for the final 5.10.0 release
+
+Review perlguts. Significant changes have occured since 5.8, and we can't
+release a new version without making sure these are covered.
 
 =head1 Tasks that only need Perl knowledge
 
@@ -36,19 +47,51 @@ 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.
 
+The addition of C<Pod::Simple> and its related modules may make this task
+easier to complete.
+
+=head2 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 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,
+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.
 
-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.
+Use Devel::Cover to ascertain the core modules's test coverage, then add
+tests that are currently missing.
 
 =head2 test B
 
@@ -56,7 +99,7 @@ A full test suite for the B module would be nice.
 
 =head2 A decent benchmark
 
-perlbench seems impervious to any recent changes made to the perl core. It
+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
@@ -86,11 +129,34 @@ 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 embed.pl/makedef.pl
 
+There is a script F<embed.pl> that generates several header files to prefix
+all of Perl's symbols in a consistent way, to provide some semblance of
+namespace support in C<C>. Functions are declared in F<embed.fnc>, variables
+in F<interpvar.h> and F<thrdvar.h>. Quite a few of the functions and variables
+are conditionally declared there, using C<#ifdef>. However, F<embed.pl>
+doesn't understand the C macros, so the rules about which symbols are present
+when is duplicated in F<makedef.pl>. Writing things twice is bad, m'kay.
+It would be good to teach C<embed.pl> to understand the conditional
+compilation, and hence remove the duplication, and the mistakes it has caused.
 
+=head2 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 C<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.
 
 =head1 Tasks that need a little sysadmin-type knowledge
 
@@ -113,17 +179,16 @@ and the core documentation (files in F<pod/>)
 
 =item 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 C<-X>, groups such as C<getpwnam> to C<endservent>, two or
-more C<=items> giving the different parameter lists, such as
+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>)
@@ -200,7 +265,7 @@ 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
+=head2 Make Config.pm cope with differences between built and installed perl
 
 Quite often vendors ship a perl binary compiled with their (pay-for)
 compilers.  People install a free compiler, such as gcc. To work out how to
@@ -214,20 +279,29 @@ 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 Relocatable perl
-
-The C level patches needed to create a relocatable perl binary are done, as
-is the work on 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 linker specification files
 
-=head2 make parallel builds work
+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.
 
-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 Cross-compile support
 
+Currently C<Configure> understands C<-Dusecrosscompile> option. This option
+arranges for building C<miniperl> for TARGET machine, so this C<miniperl> is
+assumed then to be copied to TARGET machine and used as a replacement of full
+C<perl> executable.
 
+This could be done little differently. Namely C<miniperl> should be built for
+HOST and then full C<perl> with extensions should be compiled for TARGET.
+This, however, might require extra trickery for %Config: we have one config
+first for HOST and then another for TARGET.
 
 =head1 Tasks that need a little C knowledge
 
@@ -236,9 +310,9 @@ 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 p4/rsync ships with a patchlevel.h file that usually
-defines one local patch, of the form "MAINT12345" or "RC1". The output of
-perl -v doesn't report that a perl isn't an official release, and this
+Currently perl from C<p4>/C<rsync> ships with a F<patchlevel.h> file that
+usually defines one local patch, of the form "MAINT12345" or "RC1". The output
+of perl -v doesn't report that a perl isn't an official release, and this
 information can get lost in bugs reports. Because of this, the minor version
 isn't bumped up until RC time, to minimise the possibility of versions of perl
 escaping that believe themselves to be newer than they actually are.
@@ -256,39 +330,97 @@ 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 bincompat functions
+=head2 Ordering of "global" variables.
 
-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?
+F<thrdvar.h> and F<intrpvarh> define the "global" variables that need to be
+per-thread under ithreads, where the variables are actually elements in a
+structure. As C dictates, the variables must be laid out in order of
+declaration. There is a comment
+C</* Important ones in the first cache line (if alignment is done right) */>
+which implies that at some point in the past the ordering was carefully chosen
+(at least in part). However, it's clear that the ordering is less than perfect,
+as currently there are things such as 7 C<bool>s in a row, then something
+typically requiring 4 byte alignment, and then an odd C<bool> later on.
+(C<bool>s are typically defined as C<char>s). So it would be good for someone
+to review the ordering of the variables, to see how much alignment padding can
+be removed.
 
+It's also worth checking that all variables are actually used. Perl 5.8.0
+shipped with C<PL_nrs> still defined in F<thrdvar.h>, despite it being unused
+since a change over a year earlier. Had this been spotted before release, it
+could have been removed, but now it has to remain in the 5.8.x releases to
+keep the structure the same size, to retain binary compatibility.
 
+It's probably worth checking if all need to be the types they are. For example
 
+    PERLVAR(Ierror_count, I32)	/* how many errors so far, max 10 */
 
+might work as well if stored in a signed (or unsigned) 8 bit value, if the
+comment is accurate. C<PL_multi_open> and C<PL_multi_close> can probably
+become C<char>s. Finding variables to downsize coupled with rearrangement
+could shrink the interpreter structure; a size saving which is multiplied by
+the number of threads running.
 
-=head1 Tasks that need a knowledge of XS
+=head2 Profile Perl - am I hot or not?
 
-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.
+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.
 
-=head2 IPv6
+As part of this, the idea of F<pp_hot.c> is that it contains the I<hot> ops,
+the ops that are most commonly used. The idea is that by grouping them, their
+object code will be adjacent in the executable, so they have a greater chance
+of already being in the CPU cache (or swapped in) due to being near another op
+already in use.
 
-Clean this up. Check everything in core works
+Except that it's not clear if these really are the most commonly used ops. So
+as part of exercising your skills with coverage and profiling tools you might
+want to determine what ops I<really> are the most commonly used. And in turn
+suggest evictions and promotions to achieve a better F<pp_hot.c>.
 
-=head2 UTF8 caching code
+=head2 Allocate OPs from arenas
 
-The string position/offset cache is not optional. It should be.
+Currently all new OP structures are individually malloc()ed and free()d.
+All C<malloc> implementations have space overheads, and are now as fast as
+custom allocates so it would both use less memory and less CPU to allocate
+the various OP structures from arenas. The SV arena code can probably be
+re-used for this.
 
-=head2 Implicit Latin 1 => Unicode translation
+=head2 Improve win32/wince.c
 
-Conversions from byte strings to UTF-8 currently map high bit characters
-to Unicode without translation (or, depending on how you look at it, by
-implicitly assuming that the byte strings are in Latin-1). As perl assumes
-the C locale by default, upgrading a string to UTF-8 may change the
-meaning of its contents regarding character classes, case mapping, etc.
-This should probably emit a warning (at least).
+Currently, numerous functions look virtually, if not completely,
+identical in both C<win32/wince.c> and C<win32/win32.c> files, which can't
+be good.
 
-This task is incremental - even a little bit of work on it will help.
+=head2 Use secure CRT functions when building with VC8 on Win32
+
+Visual C++ 2005 (VC++ 8.x) deprecated a number of CRT functions on the basis
+that they were "unsafe" and introduced differently named secure versions of
+them as replacements, e.g. instead of writing
+
+    FILE* f = fopen(__FILE__, "r");
+
+one should now write
+
+    FILE* f;
+    errno_t err = fopen_s(&f, __FILE__, "r"); 
+
+Currently, the warnings about these deprecations have been disabled by adding
+-D_CRT_SECURE_NO_DEPRECATE to the CFLAGS. It would be nice to remove that
+warning suppressant and actually make use of the new secure CRT functions.
+
+There is also a similar issue with POSIX CRT function names like fileno having
+been deprecated in favour of ISO C++ conformant names like _fileno. These
+warnings are also currently suppressed with the compiler option /wd4996. It
+might be nice to do as Microsoft suggest here too, although, unlike the secure
+functions issue, there is presumably little or no benefit in this case.
+
+=head1 Tasks that need a knowledge of XS
+
+These tasks would need C knowledge, and roughly the level of knowledge of
+the perl API that comes from writing modules that use XS to interface to
+C.
 
 =head2 autovivification
 
@@ -323,6 +455,11 @@ L<perlrun>.)
 
 Currently the %ENV entries are always byte strings.
 
+=head2 Unicode and glob()
+
+Currently glob patterns and filenames returned from File::Glob::glob()
+are always byte strings.
+
 =head2 use less 'memory'
 
 Investigate trade offs to switch out perl's choices on memory usage.
@@ -348,8 +485,57 @@ 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 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 B<your> platform
+is using those naughty interfaces.
+
+=head2 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 C<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.
+
+=head2 Extend PerlIO and PerlIO::Scalar
+
+PerlIO::Scalar doesn't know how to truncate().  Implementing this
+would require extending the PerlIO vtable.
+
+Similarly the PerlIO vtable doesn't know about formats (write()), or
+about stat(), or chmod()/chown(), utime(), or flock().
 
+(For PerlIO::Scalar it's hard to see what e.g. mode bits or ownership
+would mean.)
 
+PerlIO doesn't do directories or symlinks, either: mkdir(), rmdir(),
+opendir(), closedir(), seekdir(), rewinddir(), glob(); symlink(),
+readlink().
+
+=head2 -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.
 
 
 =head1 Tasks that need a knowledge of the interpreter
@@ -357,12 +543,10 @@ extended.
 These tasks would need C knowledge, and knowledge of how the interpreter works,
 or a willingness to learn.
 
-=head2 lexical pragmas
+=head2 Implement $value ~~ 0 .. $range
 
-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.
+It would be nice to extend the syntax of the C<~~> operator to also
+understand numeric (and maybe alphanumeric) ranges.
 
 =head2 Attach/detach debugger from running program
 
@@ -371,23 +555,6 @@ 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 inlining autoloaded constants
-
-Currently the optimiser can inline constants when expressed as subroutines
-with prototype ($) that return a constant. Likewise, many packages wrapping
-C libraries export lots of constants as subroutines which are AUTOLOADed on
-demand. However, these have no prototypes, so can't be seen as constants by
-the optimiser. Some way of cheaply (low syntax, low memory overhead) to the
-perl compiler that a name is a constant would be great, so that it knows to
-call the AUTOLOAD routine at compile time, and then inline the constant.
-
-=head2 Constant folding
-
-The peephole optimiser should trap errors during constant folding, and give
-up on the folding, rather than bailing out at compile time.  It is quite
-possible that the unfoldable constant is in unreachable code, eg something
-akin to C<$a = 0/0 if 0;>
-
 =head2 LVALUE functions for lists
 
 The old perltodo notes that lvalue functions don't work for list or hash
@@ -398,27 +565,15 @@ slices. This would be good to fix.
 The old perltodo notes that lvalue functions don't work in the debugger. This
 would be good to fix.
 
-=head2 _ prototype character
-
-Study the possibility of adding a new prototype character, C<_>, meaning
-"this argument defaults to $_".
-
-=head2 @INC source filter to Filter::Simple
-
-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.
-
 =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 UNITCHECK
+=head2 delete &function
 
-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.
+Allow to delete functions. One can already undef them, but they're still
+in the stash.
 
 =head2 optional optimizer
 
@@ -456,12 +611,6 @@ instated.
 
 The old perltodo notes "Look at the "reification" code in C<av.c>".
 
-=head2 switch ops
-
-The old perltodo notes "Although we have C<Switch.pm> in core, Larry points to
-the dormant C<nswitch> and C<cswitch> ops in F<pp.c>; using these opcodes would
-be much faster."
-
 =head2 What hooks would assertions need?
 
 Assertions are in the core, and work. However, assertions needed to be added
@@ -471,11 +620,23 @@ investigate what hooks would need to be added to make it possible to provide
 the full assertion support from a CPAN module, so that we aren't constraining
 the imagination of future CPAN authors.
 
+=head2 Properly Unicode safe tokeniser and pads.
 
+The tokeniser isn't actually very UTF-8 clean. C<use utf8;> is a hack -
+variable names are stored in stashes as raw bytes, without the utf-8 flag
+set. The pad API only takes a C<char *> pointer, so that's all bytes too. The
+tokeniser ignores the UTF-8-ness of C<PL_rsfp>, or any SVs returned from
+source filters.  All this could be fixed.
 
+=head2 The yada yada yada operators
 
+Perl 6's Synopsis 3 says:
 
+I<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.
 
 =head1 Big projects
 
@@ -484,11 +645,15 @@ of 5.10"
 
 =head2 make ithreads more robust
 
-Generally make ithreads more robust. See also L<iCOW>
+Generally make ithreads more robust. See also L</iCOW>
 
 This task is incremental - even a little bit of work on it will help, and
 will be greatly appreciated.
 
+One bit would be to write the missing code in sv.c:Perl_dirp_dup.
+
+Fix Perl_sv_dup, et al so that threads can return objects.
+
 =head2 iCOW
 
 Sarathy and Arthur have a proposal for an improved Copy On Write which
@@ -503,3 +668,9 @@ Fix (or rewrite) the implementation of the C</(?{...})/> closures.
 
 This will allow the use of a regex from inside (?{ }), (??{ }) and
 (?(?{ })|) constructs.
+
+=head2 Add class set operations to regexp engine
+
+Apparently these are quite useful. Anyway, Jeffery Friedl wants them.
+
+demerphq has this on his todo list, but right at the bottom.