This Week on perl5-porters (1-7 May 2006)

This Week on perl5-porters - 1-7 May 2006

   Let's change perl's internal hash function, shall we?

Topics of Interest

The Win32/Wince leveraged buy-out merger

   Vadim reminded the patch-meisters, (and clearly the man has been
   revising his classics) to apply the large Win32 patch that Yves Orton
   had posted, so that they could continue the process.

     Smelly socks!
     http://xrl.us/mekd

   Which must have been applied, for a little while later Vadim posted
   further tweaks to the Wince side of things.

     One less source file!
     http://xrl.us/meke

   As well as some Makefile.ce goodness

     http://xrl.us/mekf

"state" variables featured in "blead"

   Rafael Garcia-Suarez ironed out some of the bigger show-stoppers in
   his state variable work, and was thus able to commit the first draft
   to "blead". Arrays and hashes aren't done yet, but as of now, we have
   an elegant solution to the perennial "my $var if 0" problem.

   Nicholas Clark was impressed, and tried out a snippet of code, that
   Rafael turned into a test for a brand new t/op/state.pl.

     Coup d'état
     http://xrl.us/mekg

Is "socketpair" available everywhere?

   Jan Dubois was looking at the section in "perlport" where it says that
   "socketpair" is not available on Win32 and a number of other
   platforms. He thought that it was currently emulated on all platforms
   that did not provide a native implementation. If so, it would mean
   that the section could be quietly dropped.

   Alex Waugh mentioned that it's available natively on RISC OS, so if
   nothing else, that could be removed from the list.

     Going native
     http://xrl.us/mekh

Support for inside-out classes

   Anno Siegel delivered a two part patch to improve the implementation
   of inside-out classes. Part one deals with perl itself, and the second
   part reaches out into the core library and expands "Hash::Util". Anno
   also provided a demo to show how it worked.

   Yves Orton was quite enthusiastic, Randy W. Sims, markedly less. David
   Golden had a close look at the patch and explained clearly what he
   thought was going on, and pointed out some issues where the
   implementation was a bit rough around the edges.

   Yuval Kogman thought the patch was maybe not general enough, and
   suggested some avenues to explore, other than just Inside-Out objects.
   David Golden and Abigail discussed issues such as backwards
   compatibility at length.

   Rafael announced that he was happy with the intent of the patch.
   Nicholas Clark caught an error that Anno set about correcting.

     http://xrl.us/meki

   Obligingly, Anno summarised where he was going from here with the
   patch. In the end he retired the patch and set about doing something
   better.

     http://xrl.us/mekj

     "U" magic in February
     http://xrl.us/j63s

Hashing algorithms

   Jarkko Hietaniemi was looking at hash functions, and stumbled across a
   page full of them. Perl uses the "One-at-a-Time" algorithm. Except
   that we don't, although the comments say we do. Except, if you have
   enough coffee and look again, we really do.

   Yves Orton benchmarked a series of hashing algorithms to see what they
   did for perl. At a first glance, it looked like "One-at-a-Time" was
   rather slow, especially in comparison to another hashing function
   named (surprise!) "SuperFastHash".

   Much of the improvement is dependent on the length of the hash keys.
   Short keys show little difference, long keys can show spectacular
   improvements.

   Michael Schroeder weighed in with Buzhash, which, at the expense of a
   table of 256 "int"s, boils down to a rotate and xor per character.

     Total Hash Controversy
     http://xrl.us/mekk

Don't kill "select((select(OUTPUT_HANDLE), $| = 1)[0])"

   Abigail made an impassioned plea to keep this tricky construct in the
   documentation. The main point being that it would be of use to
   maintenance programmers, not necessarily for people starting out. A
   few people argued the issue back and forth, and Abigail maintained
   that a three line snippet would be preferable, since people could pick
   it apart and thus learn more easily about the particular parts they
   are unsure of.

     http://xrl.us/mekm

Patches of Interest

threads patches

   Jerry D. Hedden sent in a new version of a patch to threads, this time
   with much less drastic whitespace reformatting. This time around it
   was applied.

     http://xrl.us/mekn

   ... and another to add stack size support, which was the main reason
   why Jerry started to work on all of this in the first place. Applied
   as well.

     http://xrl.us/meko

What Andy Lester did this week

   Andy Lester forwarded a patch last week to tidy up one-line loops,
   specifically, bringing the lone semi colon down to the next line and
   using a "NOOP" macro. Said macro can then be used to squirrel away the
   various comments that use secret handshakes to keep source analysis
   tools happy.

   Rafael hated it. Nicholas Clark proposed a semantically equivalent
   alternative that met with the Andy seal of approval, and so Andy went
   back to refactor using the new approach.

     It's overkill of course
     http://xrl.us/mekp

   He came back after a while with new versions of doio.c and dump.c and
   wanted to know what people thought of them. Rafael must have liked it,
   since he applied the patch.

     http://xrl.us/mekq

   Along with a nice micro-optimisation for "S_find_array_subscript".

     http://xrl.us/mekr

   Andy then thought he could remove a "goto" in a section of code in
   op.c, since the only thing it does is jump over a single "if" block.
   The concept was perhaps sufficiently scary for no-one to dare apply it
   to see what would happen.

     http://xrl.us/meks

What Jarkko Hietaniemi did this week

   Jarkko tweaked "hv.c" to use a safer approach to performing the task
   of zeroing out memory.

     Know your macros
     http://xrl.us/mekt

   And cast his eyes upon pp_sys.c.

     http://xrl.us/meku

   And a tweak to shave some memory off the size of a "microperl".

     Smaller is better
     http://xrl.us/mekv

   Jarkko also added some enhancements to the "PERL_MEM_LOG"
   infrastructure, that allows very detailed logging of memory
   allocations. Jarkko hoped that someone would feel sufficiently
   inspired to write some code to munge the output and produce some
   pretty pictures to help gather a better understanding of allocation
   patterns.

     Your name in lights
     http://xrl.us/mekw

Various t/op/* tests are reviewed

   ...by yours truly, and patches applied by Rafael.

   Historians may find it of interest that the patch to context.t was the
   first ever since its inclusion, following a bug report from François
   Désarmenien nearly six years ago.

     t/op/context.t
     http://xrl.us/mekx

     t/op/grep.t
     http://xrl.us/meky

     t/op/list.t
     http://xrl.us/mekz

   And in other news, your summariser ran into a minor problem of
   resource acquisition (not enough semaphores available) to run a couple
   of tests in "blead"'s suite, and set patches to fix that up as well.

     ext/IPC/SysV/t/ipcsysv.t
     http://xrl.us/mek2

     ext/IPC/SysV/t/sem.t
     http://xrl.us/mek3

   In doing so, another minor problem arose with "fold_constants
   JMPENV_PUSH" panics. Dave Mitchell sorted this out, but you'll have to
   wait for next week's exciting episode to find out how (this is due to
   a severe warp in the space-time continuum, in that the summary is
   *really* late this week).

     That's not supposed to happen
     http://xrl.us/mek4

Watching the smoke signals

Smoke [5.9.4] 28069 FAIL(M) MSWin32 WinXP/.Net SP2 (x86/2 cpu)

   The recent work done by Yves and Vadim blew away a couple of
   assumptions. Sadahiro Tomoyuki identified the source of the problem. A
   brief flurry of patches had it fixed up quickly.

     http://xrl.us/mek5

Smoke [5.9.4] 28108 FAIL(XM) MSWin32 WinXP/.Net SP2 (x86/2 cpu)

   Another problem showed up, this time relating to threads.

     http://xrl.us/mek6

Smoke [5.8.8] 28115 FAIL(M) MSWin32 WinXP/.Net SP2 (x86/2 cpu)

   And a final one, where perl was built and yet managed to forget to
   link in a "Perl_*" function, because the export list for the linker
   had become messed up. Sorted out by Steve Hay and Nicholas Clark.

     http://xrl.us/mek7

New and old bugs from RT

Change 22258 causes test failures on AFS (#38698)

   A recent change to a ext/IO/t/io_unix.t to permit a fall-back to /tmp
   if socket creation fails in the current directory causes grief on AFS
   file systems. People tried to figure out how to work around this added
   twist. Mike Guy wondered it it wouldn't be easier to figure out first
   why the socket was failing in the current directory in the first
   place, then maybe people wouldn't have to deal with this new case.

     http://xrl.us/mek8

"rcatline" doesn't stringify references (#39037)

     and maybe it should
     http://xrl.us/mek9

5.8.8 lib/ExtUtils/t failures (#39055)

   pal@hp sent in some patches to make "ExtUtils" more robust in the face
   of super-fast hardware.

     http://xrl.us/mema

"readline" the last line with no newline (#39060)

   Mark Martinec observed that when the last line of a file lacked a
   newline, he would observe "Bad file descriptor" errors, and supplied
   some code to show how to reproduce the problem

     http://xrl.us/memb

"Data::Dumper" and numeric scalars (#39062)

   Brad Baxter noticed that "Data::Dumper" would sometimes quote a scalar
   that would otherwise not need quotes, as it was numeric.
   Unfortunately, he wasn't able to pin the change in behaviour down any
   more accurately than between 5.6.1 and 5.8.7.

     http://xrl.us/memc

non-portable static libraries on AMD64 Linux (#39068)

   This was a problem related to linking with "-fpic" as opposed to
   "-fPIC". Debate raged over how to get it sorted out in "Configure".

     http://xrl.us/memd

Choosing vendor install paths (#39069)

   A similar problem, for which the build infrastructure offers a couple
   of alternatives.

     http://xrl.us/memf

Perl locale disagrees with Linux sort (#39087)

   When locales are in use, Perl doesn't sort the same way as the GNU
   sort program in Linux, nor PostgreSQL Sadahiro Tomoyuki explained that
   perl isn't making this stuff up as it goes along, merely using
   whatever C's "strxfrm" function cares to return.

     So what are the others using?
     http://xrl.us/memg

Overloading Regexp and infinite recursion => SEGV (#39090)

   Andreas Koenig showed how overloading "" and adding a dash of "qr//"
   into the mix can produce a core dump.

     http://xrl.us/memh

deprecated $# treats 0 specially (#39097)

   Ruud Affijn showed what strange and wonderful things can happen when
   you embed a newline in the "#$" variable. Which you shouldn't be doing
   anyway as its usage is deprecated after all. Andy Dougherty traced the
   behaviour all the way back to perl 1.010.

     Good novelty value
     http://xrl.us/memi

"Pod::Html" error stops CPAN install/test of "Pod::Readme" (#39098)

   This bug highlighted the issue of what to do when installing a POD
   file as a man page, and the POD is malformed. Should the file be
   skipped? Should the installation be aborted?

     Halt and Catch Fire
     http://xrl.us/memj

Perl5 Bug Summary

     14 opened + 18 closed = 1523
     http://xrl.us/memk

New Core Modules

   *       Encode version 2.16 was released by Dan Kogai.

             http://xrl.us/memm

In Brief

   Peter Dintelmann followed up on the thread last week about length
   specifiers in "unpack"'s mini-language and came up with a
   documentation patch, first for "maint", and then for blead.

     http://xrl.us/memn

   Since "${^WIN32_SLOPPY_STAT}" is in "blead", Rafael called for some
   documentation, to explain what it does. Jan Dubois complied.

     http://xrl.us/memo

   By the same token, Jan also clarified hard link support on Windows.

     http://xrl.us/memp

   Mohammad Yaseen had some problems building Perl modules in
   non-standard locations. There was the usual chorus of advice about
   "PREFIX" and "PERL5LIB" but the really interesting news from the
   thread was that Randy W. Sims mentioned that Module::Build now (as in
   0.28) supports "ExtUtils::MakeMaker"'s "PREFIX" functionality.

     http://xrl.us/memq

   Things seemed to be moving along for Mohammad. After having
   successfully built perl on z/OS, he was having trouble dealing with
   the semantics of environment variables. Dominic Dunlop guided him
   through the minefield.

     http://xrl.us/memr

   Dominic requested more information about Perl on Windows 98. Even the
   original poster thought that it probably wasn't worth the effort to
   pursue any further.

     http://xrl.us/mems

   A few more data points on the issue of "taint" and "fork" on Win32,
   courtesy Perlmonks.

     http://xrl.us/memt

   Paul Johnson returned to Adam Kennedy's question about how to tell
   whether a file handle is seekable, as he had run into pretty much the
   same issue with "IO::Compress:Zip". In the end he simply documented
   that trying to do X with Y just does not work.

     http://xrl.us/memu

   Shlomi Fish found a Heisenbug with "perl -d". Dave Mitchell confirmed
   that it is fixed in "blead". Andreas Koenig confirmed that it was
   fixed with a Heisenpatch.

     Now you see it. Umm...
     http://xrl.us/memv

   Ash Berlin spotted a couple of places in perlop.pod with incorrect
   "L<...>" markup.

     Try writing the above sentence in POD yourself
     http://xrl.us/memw

   Nicholas Clark discovered that GCC does not conform to the C standard,
   section 6.8.6.4. Marcus Holland-Moritz comforted him with the idea the
   Intel compiler gets it wrong too.

     A void hate
     http://xrl.us/memx

About this summary

   This summary was written by David Landgren. My humble apologies for
   the tardiness, Real Life kept me busy this week.

   If you want a bookmarklet approach to viewing bugs and change reports,
   there are a couple of bookmarklets that you might find useful on my
   page of Perl stuff:

     http://www.landgren.net/perl/

   Weekly summaries are published on http://use.perl.org/ and posted on a
   mailing list, (subscription: [email protected]). The
   archive is at http://dev.perl.org/perl5/list-summaries/. Corrections
   and comments are welcome.

   If you found this summary useful or enjoyable, please consider
   contributing to the Perl Foundation to help support the development of
   Perl.


-- 
"It's overkill of course, but you can never have too much overkill."