This Week on perl5-porters - 11-17 September 2006
"Now to move a huge pile of bugs out of my rt.cpan.org queue and into
Randy's. THUD" -- Michael G. Schwern, making "MakeMaker" lighter.
Topics of Interest
Adding macros to Perl5
Jim Cromie followed up an old message from Salvador Fandiño about
better assertion support in perl. He went through the repository and
dug out all the patches, but when he applied them to blead it wouldn't
compile.
http://xrl.us/ru3n
threads causing smoke trouble on Win32 again
Steve Hay reported intermittent hangs when smoking threads on Win32.
He gathered a bit more information by running the tests manually, but
wasn't able to get things to fail reliably. Dave Mitchell muttered
something about race conditions in thread finishing, but wasn't able
to recall precisely what it was that he had noticed.
Jerry D. Hedden checked in a patch elsewhere to clear this up this
week.
The race is on
http://xrl.us/ru3o
Safe signals and "SIGSEGV"
Rafael Garcia-Suarez wondered whether "SIGSEGV" should be delivered by
default in unsafe mode, and pointed to a bug report in Mandriva Linux
that exposed the problem. Dave Mitchell tended to agree, and suggested
that "SIGBUS" and "SIGILL" be thrown in as well.
Mike Guy was in full agreement, and made a list of six points that
needed to be taken into consideration.
"This is your Captain. We are about to attempt a crash landing"
http://xrl.us/ru3p
Problems with "(??{...})" in blead
Yves Orton was taking the latest engine for a spin and noticed that
"Regexp::Common" revealed a problem with how "(??{...})" and
backtracking no longer play nicely together.
Dave Mitchell admitted that he must have backed over something in
"re_eval" and promised to straighten it out when he had a few moments.
Yves proposed one way of fixing it, after having taken a look at (and
understood) how it currently works. Dave begged Yves not to go down
that road, since it would rely on infrastructure that Dave is
currently in the process of ripping out and replacing.
I hear shiny
http://xrl.us/ru3q
"Acme::Meta" is broken again
Andreas König noticed that change #26867 in blead resulted in
"Acme::Meta" becoming unbuildable. Nicholas Clark noted that this was
the second time that it had been broken, and wondered if the most
expedient solution was simply to add "Acme::Meta" to the core.
Seriously though, the question to be asked was is what it does
considered appropriate behaviour, and thus deserving of proper
support? In which case regression tests need to be added to the test
suite ("Acme::Meta" plays fast and loose with stashes -- symbol table
hashes). Rafael proposed a patch to "Acme::Meta" which restores full
functionality (?) whilst keeping the the recent speed optimisations
that have been made in the neighbourhood.
Acme Development Company
http://xrl.us/ru3r
Help me-e-e-e-e
After a certain Chandra Sekaran posted a vague bug report that
mentioned PERL, LDAP and the MS Event Viewer, Dominic Dunlop provided
a detailed response on what steps Chandra should take to get the
problem fixed, which prompted Andy Dougherty to thank Dominic for his
kindness and patience over the years when dealing with such reports.
And he didn't even mention uppercase
http://xrl.us/ru3s
Similarly, Dominic patiently walked a guy named Richard through trying
to identify why perl was crashing in a SpamAssassin/Mac OS/X
environment.
http://xrl.us/ru3t
More on trimming OPs
Dave Mitchell took a look at Jim Cromie's work on combining "op_next"
and "op_sibling" in the opcode structure, and wanted to obtain better
figures on what the memory difference would be. Dave thought that the
massive creation of SVs that come about when one does any sort of work
would drown out the savings made in shrinking the opcodes.
As Jim had been encountering difficulties in getting the patch to work
correctly, he had been asking for help (which then in turn would allow
such benchmarks to be obtained). Dave Mitchell suggested an elegant
trick that at least defers having to get it to work.
Just add an extra dummy field to the structure and see how much the
overall programs grows. One could then conclude that if Jim were to
succeed in his efforts, the program would shrink by an equivalent
amount in the other direction.
Depending on the code, the change is negligible or significant. More
real-world code samples will be needed to see whether it is worth
pursuing. Joshua ben Jore reminded him that "B::Deparse",
"Data::Dumper" must not be broken because of such changes.
Union structure blues
http://xrl.us/ru3u
David Nicol set about trying to prod the compiler into producing large
amounts of code to shed light on Jim's improvements.
http://xrl.us/ru3v
Core support for "Data::Bind"
Chia-liang Kao explained what new core support would be required to
make "Data::Bind" (which provides Perl6-style semantics for subroutine
arguments) a little less of a kluge. The main problem is to have a
read-only lexical alias that points to a regular read-write lexical.
The easy way out would be to hang the information off the target SV,
but then the original SV naturally becomes read-only as well, which is
exactly what we're trying to avoid. Thus some sort of shim layer is
needed between the alias and the original to get a chance to to the
deed, which caused chromatic to mutter something out bestowing a new
vtable upon an SV.
Rick Delaney and Rafael Garcia-Suarez debated syntax. Nicholas Clark
and Larry Wall debated implementation issues (with an eye to backwards
compatibility: any number of suitable solutions exists, but they would
break existing XS code. Not good).
... and in the data bind them
http://xrl.us/ru3w
Taint and memory usage
Xho Jingleheimerschmidt wondered why running a program with taint
checks appears to double the amount of memory required. This can be a
problem on lean machines. Xho wanted to know if there is a work-around
for it, or failing that, an explanation of why it occurs.
I figured out one part of the problem and will have posted a partial
reply next week, but you'll have to wait until then and see whether an
internals guru picks up the ball and runs with it.
Getting ahead of myself
http://xrl.us/ru3x
Dual-lifing "Devel::DProf"
Andy Lester, evidently having too much spare time on his hands,
thought it would be a good idea if he were to take care of
"Devel::DProf". Except that it's noted on CPAN that Ilya Zakharevich
is already the author. Then again, the version bundled with "blead" is
different, anyway.
Ilya was rather non-committal on the idea, citing that while a more
portable codebase is desirable, the module is too intimately tied to
perl's internals for it to be easy to make a one-size-fits-all
distribution. Rafael thought that it might lead to a twisty maze of
"#ifdef"s.
Be that as it may, Andy was most interested in making improvements to
the "dprofpp" end of things. (Which makes me wonder whether the
distribution needs to be some dimorphic beast: one side that gathers
profiling information, and the other side that does the reporting).
More like dual-heading it
http://xrl.us/ru3y
Patches of Interest
Race condition fixes for threads
Jerry D. Hedden posted a patch to fix what he thought was the cause of
the race conditions that have been seen (above) with threads. Dave
Mitchell appreciated the effort, but rebuked Jerry for mixing in
trivial stylistic changes with serious open-heart surgery on mutexes.
It becomes difficult to see what is important, makes it harder to
track changes, and increases the workload of the "maint" pumpking who
has to try and merge this stuff.
http://xrl.us/ru3z
So Jerry redid the patch to make it easier for people to follow along
at home. Rafael smoked the patches on a hexaprocessor box, gave them a
clean bill of health, and so they were applied.
Flying colours
http://xrl.us/ru32
C++: Solaris CC now compiles "perl"
Jarkko Hietaniemi sent in an update concerning his work to get the
perl sources compiling with C++. It caused the Win32 compile to bomb,
so Yves Orton rewrote the nasty bits and got it to work.
http://xrl.us/ru33
And then some more from Jarkko:
http://xrl.us/ru34
Jarkko also rewrote the "Encode"-generated code to make it safe for
C++ compilers.
http://xrl.us/ru35
How to handle "(?=)" and "(?<=)" properly
Yves Orton added more shiny goodness to the regular expression engine,
this time boosting the performance of zero-width lookahead assertions.
In the benchmarks that Yves had available, this was the last area
where Python was previously outperforming Perl.
Getting your bearings
http://xrl.us/ru36
Elsewhere around the engine, Yves started to add hooks into it to pave
the way for making a pluggable regular expression engine. (Which may
lead, for instance, to Yves and Dave Mitchell's work in blead one day
making it back to maint. Or running the PCRE engine inside Perl).
http://xrl.us/ru37
VMS goodness for the "Module::Build" beta
Craig Berry sent Ken Williams a patch to reduce the number of failures
observed when testing "Module::Build". The situation is still not
perfect, but Craig felt certain that this batch of changes would not
create problems on other platforms.
http://xrl.us/ru38
Fixing "\N{...}" in regular expressions
A couple of months back, Sadahiro Tomoyuki showed that "/a\N{PLUS
SIGN}b/" is parsed as "/a+b/" instead of the more Do-What-I-Meanish
"/a\+b/". Yves Orton delivered an impressive patch to correct that
behaviour. Tomoyuki went through the patch with a fine-toothed comb
and made many suggestions. H.Merijn Brand applied it.
Unicode unified
http://xrl.us/ru39
Patching win32.c to fix bugs #38723 and #39531
Andrew Savige mailed in a patch to correct a couple of Windows bugs
dealing with backticks. In fact, there were two patches, one for maint
and one for blead. How thoughtful.
Yves went over it and gave it the thumbs up. Rafael took it for a spin
on an SMP box but the tests would hang from time to time. But since
there is a net improvement, it's all gone in, and the test has been
marked TODO until such time as Yves or someone else can take a closer
look.
http://xrl.us/ru4a
Watching the smoke signals
Smoke [5.9.4] 28821 FAIL(XF) OSF1 V5.1 (EV6/4 cpu)
Jarkko discovered that Finnish locales, threads and regexps was a
potent brew that caused all sorts of smoke to come flying out of his
machine. Yves started to sift through the evidence to look for what
was going wrong.
After a short while, he hacked up a quick and dirty fix that consisted
of disabling "study" for UTF-8 strings. And after another look he
didn't feel so bad about the idea, since the code seemed to indicate
that it couldn't work anyway.
Rafael had another look at the patch that had given rise to the
problems, and noted that it was only the test part of the patch that
appeared to be in error.
Yves finally hit paydirt. The test was actually correct. The code was
wrong. Looking at old patch from Ilya Zakharevich some time last
century, where a change from double- to single-quoting of some
embedded Perl code meant that from that time on, the test has been
patiently studying a stringified reference instead of a reference to a
string, and that UTF-8 and "study" has been broken forever. Jarkko was
lost for words. But then quickly recovered and gave Yves his next
challenge.
Jarkko and Yves then discussed how Perl should have really implemented
UTF, properly. Yves hoped that the Perl 6 crowd have learnt their
lessons well.
I never liked studying, anyway
http://xrl.us/ru4b
Smoke [5.9.4] 28849 FAIL(m) MSWin32 WinXP/.Net SP2 (x86/2 cpu)
Sadahiro noticed a that a declaration list contained a statement,
which is a no-no for some compilers. Once that was fixed the smoke
cleared up.
http://xrl.us/ru4c
Smoke [5.9.4] 28848 FAIL(Fm) OSF1 V5.1 (EV6/4 cpu)
Jarkko noted another failure, that occur when the locale in use uses a
comma as a decimal point. This reminded H.Merijn Brand of Stupid
Locale Tricks to try with Windows, and John Peacock wondered how he
could better test "version.pm" to deal with this stuff.
http://xrl.us/ru4d
New and old bugs from RT
ref counting bug (#21945)
Steve Peters thinks this is a heisenbug, so he asked for other people
to take it for a spin, just in case he was seeing things (or not).
http://xrl.us/ru4e
XSUB.h version check may fail due to locale (#37714)
Rafael hauled out a previously unknown macro into the light to fix up
this bug. John Peacock was most appreciative, and begin to fold it
into "version.pm", when Rafael came up with an even better patch. So
John patched Rafael's patch to do some other things he needed it to
do.
http://xrl.us/ru4f
-0.0 loses signedness upon numeric comparison (#39875)
Michael G. Schwern wondered why this bug was still open, since there's
a patch ready and waiting to be be applied.
ping
http://xrl.us/ru4g
Re: File::Spec->case_tolerant() should return true on Cygwin (#40103)
Michael also wasn't sure what was case tolerant and what wasn't, at
proposed a simple test to solve the issue.
A sensitive matter
http://xrl.us/ru4h
g++ 2.95.3 on Solaris 8 can't compile perl.h "__attribute__" (#40317)
Christopher D. Malon was having trouble getting an old GNU C++
compiler to compile an XS module. No solution appeared to be
forthcoming immediately.
http://xrl.us/ru4i
Question? (#40322)
A question was asked about how to tell what "nalloc" routine was
compiled into perl, and an answer was given.
http://xrl.us/ru4j
Documentation patch for perlfunc.pod (#40327)
Merijn B. (the *other* Merijn) noted one passage in "perlfunc"
concerning "stat" that was less than clear and proposed a fix. Applied
by Rafael.
http://xrl.us/ru4k
overload::Overloaded depends on bad Class->can (#40333)
Joshua ben Jore wanted to do some really weird stuff to
"overload::Overloaded", because he was trying to build an instant box
of death. This would be used to help test to ensure that an
introspective module doesn't trigger overloading or magic by accident.
http://xrl.us/ru4m
"pod2man" output is hyphenated by groff (#40344)
[EMAIL PROTECTED] noticed that the nroffish output produced by "pod2man" is
incorrectly hyphenated by "groff", and added the necessary nroff
incantation to fix it up. Rafael noted that this is fixed by Russ
Alberry's latest release of "podlators".
http://xrl.us/ru4n
Perl5 Bug Summary
12 down, 9 up, 1528 total, for an overall week-on-week decline for the
first time in a while.
stats
http://xrl.us/ru4o
and more stats
http://rt.perl.org/rt3/NoAuth/perl5/Overview.html
New Core Modules
* Ken Williams released beta version (0.2805_01) of "Module::Build".
http://xrl.us/ru4p
* Jos Boumans announced the release to CPAN of CPANPLUS version
0.074.
http://xrl.us/ru4q
* Michael G. Schwern released another iteration of
"ExtUtils::MakeMaker", now standing at version 6.30_04.
http://xrl.us/ru4r
* Michael also kicked two more kids, "ExtUtils::Command" and
"ExtUtils::Manifest". out of the MakeMaker menagerie. Randy Kobes
will take care of them.
http://xrl.us/ru4s
* Now that Audrey Tang has clarified the licensing issues
surrounding "Locale::Maketext::Simple", which is a
dependency"Params::Check", both modules have been added to the
core.
http://xrl.us/ru4t
* Russ Allbery released the latest version (2.0.5) of "podlators".
http://xrl.us/ru4u
In Brief
Turns out that Perforce does have flexible commit hooks to perform
actions when a file changes.
http://xrl.us/ru4v
Yet another person wondered how to deal with "Storable" version
mismatches.
http://xrl.us/ru4w
Jerry D. Hedden was looking at threads/shared/typemap. It was removed
in a patch by accident, and then subsequently reinstated. Jerry
wondered why, since it is a zero-length file that apparently serves no
purpose.
http://xrl.us/ru4x
And the patch to reinstate it didn't square with the APC ("Archive of
Perl Changes") repository, and left the latter in an uncertain state.
http://xrl.us/ru4y
Jonathan Rockway wanted to know whether one could compile Perl 5 for
Qtopia devices. Paul Johnson provided a couple of tips.
http://xrl.us/ru4z
Gabor Szabo wondered whether errors about the signedness of pointer
targets in Normalize.xs in 5.9.4 were the same as those in
"Net::RawIP". Whatever the case, Gabor fixed the problem with a couple
of casts.
http://xrl.us/ru42
Yves Orton finally became sufficiently annoyed by the "mktables"
executes seven time per build mazurka and decided to do something
about it. So he did. Yay! Rafael applied it. Yay!
http://xrl.us/ru43
Yitzchak Scott-Thoennes was looking at the ongoing coredumps in Cygwin
and finally suggested a one-liner involving "sv_setpvn" and "NULL".
Applied by Rafael.
http://xrl.us/ru44
We are still looking for a volunteer to work with Klocwork in order to
perform an analysis of perl code. (At the C side, that is).
http://xrl.us/ru45
Jarkko removed the probe for "-Wdeclaration-after-statement" from
"Configure".
http://xrl.us/ru46
Also, if your exotic platform has been having an environmental crisis
with blead, it may be due to Jarkko's diddling of "Perl_my_setenv()".
So the diddling was undiddled.
http://xrl.us/ru47
Premchai noted that "perlsec" talks erroneously about a "Non-Finite
Automaton" when in fact it should be talking about a Nondeterministic
Finite Automaton.
http://xrl.us/ru48
In case you hadn't noticed, JPL (the Java/Perl thing) has been removed
from "blead" and will not be present in 5.10.
http://xrl.us/ru49
Ben Morrow showed me a simple of trick to cope with what happens when
perl headers conflict with systems headers.
http://xrl.us/ru5a
David Nicol added a bit about "B::Deparse"'s failure to grok outer
lexical scopes in its BUGS section.
http://xrl.us/ru5b
About this summary
This summary was written by David Landgren.
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