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)
[EMAIL PROTECTED] 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."
