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This Week on perl5-porters (18-24 September 2006)

David Landgren
September 28, 2006 14:29
This Week on perl5-porters (18-24 September 2006)
Message ID:
This Week on perl5-porters - 18-24 September 2006

   If we fake times in our fake stat then fake futimes makes sense. But
   chown and chmod make little sense to me - only the current process can
   access the scalar so current UID is owner (and can't exec it).

   We could accept the calls and set errno to nearest code that made
   sense, or perhaps just set the mode so that fake stat saw it.

   Have we missed any more fd related calls? If there anything else that
   we can do to filehandles via perl interface that we missed?

   -- Nick Ing-Simmons, discussing how to improve "PerlIO::Scalar",
   September 1st, 2006.

Topics of Interest

Shrinking the context struct

   Nicholas Clark noticed a sly new technique to fiddle around with
   unions of structs used for dealing with contexts, which would result
   in some memory savings that had the added bonus of bringing the size
   of the structure down to 64 bytes in the ILP32 data model.

   (ILP32 means that integers, longs and pointers are all 32-bit data

   So Nicholas applied the change, and then stepped gingerly back from
   the keyboard to see what the smoke machines would make of it.

A roadmap for "MakeMaker" developments

   Michael G. Schwern posted his thoughts on what needs to be done to get
   a new stable version out the door, as well as future directions, which
   includes the desire for a major rewrite of the documentation.

   The list appeared to be furious agreement.

"__attribute__format__(__printf__..." in BSD land

   Philip M. Gollucci was having great difficulty in figuring out why gcc
   on FreeBSD was stumbling over an "__attribute__" attribute to the
   "printf" C declaration, and declared it to be a show-stopper for 5.10,
   since it breaks mod_perl2.

   He also supplied the current crop of compiler warnings when compiling


   Andy Lester wrote up a report on Klocwork, a source code analysis
   tool, comparing it to Coverity, another tool that does the same sort
   of work. Jonathon Rockway appeared interested in following up on the
   issues uncovered.

sort and 0 returns from comparison routines

   Allen Smith posed a most interesting question about sorts, in relation
   to genetics, whereby it may be cheap to compare (and thus order) X and
   Y, and is comparing Y and Z. But comparing X and Z may be
   inconveniently expensive. So he wanted to know if there was a sort
   algorithm that allowed one to punt the decision (for instance, by
   returning "undef"), and force the algorithm to use different
   comparisons to arrive at a sorted order.

   John P. Linderman thought that what Allen really needed was not a
   relational sort, but a topological sort, and suggested taking a look
   at "Sort::Topological".


C++ status report

   Jarkko Hietaniemi posted his latest patchwork to get the perl
   distribution comping with C++. The two remaining modules that still
   cause problems are "Compress::Zlib" and "Digest::SHA".

   Part of the problem with "Compress::Zlib" is that it is possibly even
   more widely used than Perl, and its authors are understandably loathe
   to give up K&R function signatures. And it seems the only way to have
   both K&R and ANSI signatures is to use horrible #if/#else botches.

Patches of Interest

Teach regex optimiser how to handle (?=) and (?<=) properly.

   Yves Orton taught us a little more about how he taught the regexp
   optimiser to make use of the information available in zero-width
   lookahead (and lookbehind) assertions.

Patch for win32.c to fix #38723 and #39531

   Andrew Savige and Yves continued to beat this patch into shape.

"Exporter" documentation

   Gabor Szabo suggested adding "use strict/use warnings/use base" into
   the documentation for "Exporter". It seemed to rub a number of people
   the wrong way.

New and old bugs from RT

XSUB.h version check may fail due to locale (#37714)

   John Peacock supplied a patch to fix this problem in "blead", and
   promised a new version of "version" soon.

"-M" isn't forbidden on the "#!" line with "-x" (#38488)

   Rafael thought that it would be difficult to resolve this problem in a
   sufficiently robust way, mainly because of whitespace issues on the
   command line.

"PL_compiling.cop_warnings" changed structure in 5.8.8? (#40352)

   This was a false alarm that Nicholas Clark figured out was because the
   code in question was based an incorrect assumption about what pointer
   to use.

getppid.t fails, all others tests pass (#40362)

   pjm at sanger reported a problem on a Tru64 platform with a test for
   the parent pid not working correctly. No takers for the moment.

     millions and millions of pids

Nested "for" loops: only internal loop is executed (#40365)

   Posting a broken program to a bug-tracker...


"File::Find" mishandles non-dangling symlinks (#40369)

   Ammon spotted a bug in "File::Find"'s code, that has probably existed
   forever, and fixed it. Steve Peters applied the change.

"h2xs" enum bug in "ExtUtils::Constant::WriteConstants" (#40381)

   Aaron Dancygier hit a problem with "enum"s created with "h2xs". Steve
   Peters thought that the bug had possibly been fixed since, and asked
   for a test case. Aaron supplied a tarball.

     Tune in next week

threads: deadlock occurred on creation of a thread while joining others 

   Tsutomu Ikegami demonstrated how to produce thread deadlocks
   (threadlocks?) more or less on demand, and noted that "blead" was
   better but not perfect. Jerry D. Hedden, having spent an inordinate
   amount of time on this issue in the recent past wanted to know if the
   fault was still observed when using the latest version (v1.42) of the
   "threads" module. When he tried, everything went swimmingly.

Unexpected empty captured match vars after match (#40384)

   Alex Davies demonstrated a bug that exposed some borderline behaviour
   with failing "s///g" matches and capture variables. Dave Mitchell
   noted that the test suite didn't exercise this problem, and wasn't
   even sure what the correct behaviour should be anyway.

     And if Dave's not sure...

"perl_destruct()" leaks "PL_main_cv" (#40388) and "perl_destruct()" 
leaks "PL_defstash" (#40389)

   Gozer demonstrated two ways to produce leaks, but Andy Dougherty was
   unable to recreate them with a fresh copy of "blead", and asked Gozer
   to check and see whether he still saw the same problems with that.

     The dynamic duo

   %SIG isn't cleared during "perl_shutdown()" (#40390)

   Gozer also went on to show that a signal handler may still be
   registered during "perl_shutdown" even though the data structures for
   them have been freed. If a signal arrives after this has occurred, bad
   things happen.

"PerlIO::encoding" doesn't handle fallback modes correctly? (#40401)

   Steve Hay was trying to bend "PerlIO::encoding" to do his bidding, but
   was not having much luck.

Compiling jpl/PerlInterpreter fails (#40403)

   Sakina Suliman was having trouble building the JPL interpreter.

     I guess that's why we pulled it

"jpl/Test" failing to run (#40404)

   Sakina then managed to get JPL to run anyway, but then ran into grief
   a little further on.

     The last JPL user on earth

"undef" and "seek" on filehandles opened to references causes segfaults 

   "buu" discovered that if you open a filehandle to an in-memory scalar,
   and then undef the scalar, perl will segfault. While this is probably
   a silly thing to do at the best of times, a segfault is perhaps a tad
   severe to indicate that it's wrong.

Perl5 Bug Summary

     One less than last week

     Get 'em while they're hot

In Brief

   The "SIGSEGV", "SIGBUS" and "SIGILL" signals are now delivered
   unsafely, paradoxically, for added safety.

   David Landgren followed up on a problem posted by Xho
   Jingleheimerschmidt, whereby running the same program under taint mode
   doubled the amount of memory used. It turned out to be a problem to do
   with using the "x" repetition operator on a list, rather than a
   scalar. Thus, the fix was easy, but the reason remains unknown.

   The Mac OS/X / SpamAssassin problem continued to roll along with
   Dominic Dunlop trying to get a handle on the problem. Alas, without

   Yuval Kogman got caught out by the interpolation of scalar references
   in a string and wondered if it was a bug or a feature. It is, of
   course, a feature, and "perlref" was amended to clarify the fact.

   Sebastian Steinlechner spotted a problem with the ordering of variable
   declarations in "IO::Socket" and got things straightened out.

   Filip Filipov wanted to know how to write "Storable" data files in
   Java, so that Perl could read them. Yuval Kogman thought that it would
   be easier to use YAML or something else. "Storable" is tied too
   intimately to Perl's internals to be used easily as an interchange

   The way perl allocates more memory than immediately (with an eye to
   reducing the amount of subsequent reallocations required) was tweaked
   slightly for 5.8.8. It turns out that this caused a problem in
   "DBD::ODBC". But knowing the cause of the problem is half way to
   figuring out the solution.

   The optimisations that Nicholas Clark introduced into inlined constant
   subroutines a while back caused new warnings to emerge in
   "File::Slurp"'s test suite. But since the code in question is somewhat
   questionable, Nicholas felt that it was working as advertised.

     Doctor, it hurts when I do this

   Yves Orton and Nicholas Clark continued to kick around the idea of a
   pluggable regexp engine. Stay tuned for more information next week.

   Adriano Ferreira added test descriptions to lib/File/Copy.t,

About this summary

   This summary was written by David Landgren. According to my records,
   last week's summary rolled the total words written past the 100 000
   words threshold.

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