"This isn't supposed to happen, obviously. It's unusual for Configure
to pick up libraries that it can't, in fact, use." -- Andy Dougherty,
commenting bug #39195
Scalar::Util::weaken, to have or have not There was further discussion of the XS version of Scalar::Util
and the fact that it offers a weaken function which is vital to
avoid resource leaks when freeing self-referential structures.
(Specifically, it offers a method from Perl-space to intervene
directly on the underlying mechanism used for managing garbage
collection).
There were five philosophers at a table http://xrl.us/mxwq
Adam Kennedy proposed Task::Weaken as an elegant way (insofar
as a wart may be considered elegant) of dealing with the problem
of trying to create a dependency on the particular Scalar::Util
version that happens to contain the weaken routine.
Not the other one http://xrl.us/mxwr
Last month, Nicholas Clark discovered some obscure bugs that could lead to race problems, with critical memory accesses not protected by mutexes, or memory allocations going astray. He managed to sort out a number of problems, and reported that there were a number of issues that would need to be addressed.
The fearsome five http://xrl.us/mxws
Yves Orton ran a post-mortem on his recent work to convert /[c]/ to /c/,
and realised that a lot of the difficulty can be traced back to the memory
allocation strategy used. By its very nature, the strategy rules out a
number of interesting optimisation possibilities, because a regexp is
built with a two-pass compilation, and during the second pass,
too much information has already been discarded, so at that point it is
already too late to be able to consider a certain number of transforms.
Save more information up front, and then you stand a better chance of being able to apply some useful optimisations to the resulting opcodes. Hugo van der Sanden wondered whether it would be possible to produce an opcode stream that would be amenable to processing by the existing peephole optimiser.
Yves wanted to push a lot of the smarts from study_chunk and regtail
into the parse phase. And wrapped up with a patch to tidy the debug
output somewhat, and improve the trie code.
Gentlemen, study your engine http://xrl.us/mxwt
Andy Lester wanted to add some consting goodness to regcomp.c and regexec.c, which would have caused Yves considerable pain, since he was in the middle of some deep core hackery, and didn't want to face the nightmare of a three-way diff.
Not now http://xrl.us/mxwu
After that, Yves delivered a verily impressive patch of new, shiny goodness
to the regexp engine. And if that wasn't enough, he also took Andy's own
consting work and folded that in as well. After a bit of adjustment due to
other patches going into blead at the same time, Rafael managed to get
everything in place and running nicely.
Right now http://xrl.us/mxwv
Juerd Waalboer wrote a very nice tutorial to help people get started with Unicode. A number of people contributed ideas and suggestions. Juerd sifted through these and produced a second version. As we went to press, inclusion in the core was pending.
Unicode decoded http://xrl.us/mxww
sprintf and tainted format strings Dave Mitchell revisited the sprintf('%n') issue that made the
headlines back in December, and thought that it might be wise to
apply taint checks to the format string (the first argument to
sprintf, proposed a relaxed or strict interpretation to what
tainting would imply and asked for opinions on the matter.
Andy Lester favoured the strict approach (any use of a tainted format string fails), but recalled that the idea had been dismissed rapidly when put forward during the previous discussions. Steve Peters thought that it was more a case of being set aside than anything else, and expressed surprise at the fact that format strings do not already have taint checking.
Rick Delaney wondered what exactly did Steve and Dave mean, and put forward a couple of snippets to see if he understood the issues.
Just when you thought it was safe http://xrl.us/mxwx
Jarkko Hietaniemi was led astray by a somewhat unhelpful Use of
uninitialized value in hash element warning caused by overloading,
and wondered if a better message could be generated if overloading
was involved.
While not directly answering Jarkko's question, Joshua ben Jore
mentioned that even more overloading fun can be had when using
Devel::Cover, since applying defined to an object will trigger
stringification there, but not during normal execution. Paul Johnson
was most surprised to hear this, and asked for a test case. David
Landgren provided a small example that exposes the problem.
Yves Orton confirmed that he had run into this problem when
developing Data::Dump::Streamer, and had had to jump through
considerable hoops to work around it.
Gun, meet foot http://xrl.us/mxwy
Yves Orton noticed a problem due a recent tweak to Test::Harness,
and fixed it so as to stop harness from printing the summary table
header for each row. Which does, it should be agreed, get tedious
after a while.
No more excessive scrolling http://xrl.us/mxwz
At about the same, Andy Lester changed t/TEST to queue up the
names of the tests that fail, to dump them at the end of the run.
This means one gets all the failing tests in one convenient chunk.
No more scrolling back http://xrl.us/mxw2
In his ongoing quest to const, Andy Lester sent in some refactoring
for av.c, which crushed some incorrect uses of SvREFCNT_inc,
removed unnecessary temporary variables and brought the usual
suspects into line.
http://xrl.us/mxw3
And a parameter to Perl_magic_existspack in mg.c that could
be made const.
http://xrl.us/mxw4
And a similar treatment for Perl_gv_check in gv.c.
http://xrl.us/mxw5
Pod::Html should not convert "foo" to "foo" Gisle Aas hated this mis-feature, since most modern fonts produce a
spectacularly ugly result. After a bit of a detour into the realm of
troff, it was decided to just use plain double-quotes instead.
http://xrl.us/mxw6
Jarkko found that Sébastien Aperghis-Tramoni's tests in Dynaloader.t were too platform-specific to be useful. After a bit of discussion it was decided to loosen up the test which attempted to trap the message generated when the loading of a non-existent shared library is attempted.
Eggs, bacon, sausage and spam http://xrl.us/mxw7
eval "sub { \$foo = 22 " (#37231) This used to leak memory (that is, trying to eval a broken
subroutine definition). Dave Mitchell made it leak less. And then
after sitting back and looking at his handiwork, Dave made completely
water-proof. Nicholas Clark still managed to poke a hole in it.
Unruffled, Dave countered with a King's Gambit that appeared to
keep any remaining errant allocations in cast-iron casing.
http://xrl.us/mxw8
IPC::Open2::open2 failures (#39127) Dave Mitchell had a look at the source code, and noted that there was
a race condition depending on whether the child dies before or after
the parent tries to write to it. Furthermore, there is no easy way to
fix the problem as is, which is why IPC::Run may be a better
alternative all round. Dave suggested a documentation patch to
clarify the situation.
http://xrl.us/mi7r
IO::Socket::connect returns wrong errno on timeout (#39178) "mlelstv" showed some discrepancies in error messages depending on
whether it was the first or subsequent time that a socket connection
failed, and traced it down to a $! not being cleared before a
system call.
http://xrl.us/mxw9
qr// flags (#39185) "johnpc" reported a bug in patterns using qr// flags. Dave Mitchell
reported that this had been fixed in blead, but not yet backported
to the maintenance branch.
http://xrl.us/mxxa
Select your continent (#39186) Mark-Jason Dominus was in the middle of configuring his CPAN client
when things started to go horribly wrong. Andreas Koenig wanted to have
a look at Mark's MIRRORED.BY file. Mark took one look at the file and
saw that it was corrupt (well, empty), and therefore knew what to do.
Delete and start over http://xrl.us/mxxb
perlfunc on reverse in scalar context (#39187) Ted Pride had never noticed that reverse also works on scalars:
my $rev = reverse('forward'); # $rev contains drawrof
mainly because the documentation is slightly too clever for its own good.
http://xrl.us/mxxc
Sriram Madduri had configured a perl build, but at link-time the
build failed with some unknown libraries that Configure had
specified. Andy Dougherty spotted what he thought was the cause
of the problem, but we didn't hear back from Sriram, so we don't
know if it's fixed.
http://xrl.us/mxxd
File::BOM hangs during test (#39211) Redirected to the module author. File::BOM isn't core.
y otras chicas del montón http://xrl.us/mxxe
If it's causing the expected behaviour...
it's not a bug http://xrl.us/mxxf
$] or $^V (#39214) Benjamin Smith wished that $] or $^V were constant-folded. This
could be useful, because then one could include sections of code for
specific versions of Perl that would be optimised away at compile
time if not applicable. Unfortunately, since these variables are,
well, variable, and not constant (in other words, you may assign
to them), this isn't going to work.
http://xrl.us/mxxg
Pod::HTML should use &entities; for quotes (#39215) Johan Vromans thought that this would be a nice idea. Gisle Aas
explained why it might be a bad idea, and that in any event, Pod::HTML
had been tweaked to no longer emit the pugly `` and '' blots.
http://xrl.us/mxxh
nmake (#39226) William C. Smith wanted to compile Perl with nmake. Yves showed him
how to do just that.
http://xrl.us/mxxi
The previous week's bug summary, omitted from the previous summary (oops):
7 created + 12 closed = 1507 http://xrl.us/mxxj
And this week:
8 created and 22 (!) closed = 1493 http://xrl.us/mxxk
Hey! we broke through the 1500 barrier!
Now, with added shinyness http://rt.perl.org/rt3/NoAuth/perl5/Overview.html
Version 0.60 of version had a bit of trouble settling down in blead, but
after smoothing a few rough edges it all came together.
http://xrl.us/mxxm
Test-Harness 2.60 was released by Andy Lester.
http://xrl.us/mxxn
Sys-Syslog 0.14 was released by Sébastien Aperghis-Tramoni,
featuring a number of bug fixes, and enhancements to the both the
code and test suite.
http://xrl.us/mxxp
Marcus Holland-Moritz documented and completed a few holes in the orthogonality of literal string macros, mainly as a service to XS developers. Applied.
http://xrl.us/mxxq
Anno Siegel had some difficulties adding a core module because it
was building man pages when it was not supposed to. Rafael provided the
necessary MakeMaker magic to make it do the right thing at the right time.
http://xrl.us/mxxs
Andy Lester's second refactoring of pp_sys.c from last week went in as change #28279.
http://xrl.us/mrb3
Alberto Simões thought that the problem of regexp slowness with
$' and $` could be solved elegantly by making them lexical.
Dave Mitchell demonstrated why this was not possible (existing code
would break).
http://xrl.us/mxxt
Torsten Foertsch wanted to know how to trap a warning generated at global destruction time. The test infrastructure doesn't appear up to the task, because at global destruct time, all the tests have long since finished. chromatic recommended running the test in a child, and examining its output.
http://xrl.us/mxxu
perlhack.pod was confused about POPSTACK , so Dave Mitchell and
Jan Dubois tightened the documentation. Deep core hackers rejoiced.
http://xrl.us/mxxv
Dave also improved the -Dpv parser debugging output.
http://xrl.us/mxxw
Philip M. Gollucci was having trouble with
Perl_croak and nullch at patch level 27529.
http://xrl.us/mxxx
Jarkko noticed that there are no execute bits on semaphores on Mac OS/X, and tweaked the documentation to clarify the situation.
http://xrl.us/mxxy
Alex Davies cooked up a patch to shrink the object size for pp_sys.c , but as the savings came at the cost of code legibility, with no apparent run-time benefit, Rafael chose to decline it.
http://xrl.us/mxxz
This summary was written by David Landgren. Yes, late enough to be next week's summary. Sorry, this week I have been dealing with assorted crises.
Last week's summary attracted a response from Dave Nicol, who explained his linked list master plan in more detail.
Action stations http://xrl.us/mxx2
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: perl5-summary-subscribe@perl.org ). The archive is at http://dev.perl.org/perl5/list-summaries/ . Corrections and comments are welcome.
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