This Fortnight on perl5-porters - 28 September-12 October 2008
"... because a git repository is a collection of assembled changes,
not a linear progression, using a commit ID as a way to find out where
your code came from doesn't work. This is not git's fault but is an
issue with every distributed version control system (SVK tries to
pretend otherwise). You could perhaps use a combination of the git
repository you pulled from and the last commit ID, but [...]
fundamentally the idea is gone. It's a small price to pay." -- Michael
G. Schwern, coming to terms with the future.
Topics of Interest
$VERSION in "Opcode"
The tangent regarding the issue of module version numbers and the
techniques to deal with them continued apace over the last fortnight.
The core of Matt S. Trout's argument over "version.pm" is that it
injects a method into "UNIVERSAL", and this, in an of itself, produces
action at a distance, even when "version.pm" is not at fault. The
problem shows up when "version.pm" is used incorrectly by third-party
code, and the resulting errors are very hard to track down.
All that being as it may, Matt appreciates the value of the version
comparison code available, and would like to be able to get at it,
while leaving "UNIVERSAL" untouched. Otherwise, it's akin to modifying
$[ or $/ at the global level. Tom Christiansen concluded that only the
highest level code should be putting things into "UNIVERSAL", not by
proxy via the use of other modules.
universal language
http://xrl.us/oudw3
http://xrl.us/oudw5
Later on, in a particularly magnanimous gesture, John Peacock
announced that he had a patch that would do all that Matt wanted and
more, and asked if Matt was satisfied by it.
UNIVERSAL::VERSION and version.pm
http://xrl.us/oudw7
Y2038 branch
Steve Hay took Michael G. Schwern's Y2038+ code for a spin in the land
of Windows, and made a few adjustments to have it play nicely with the
compilers there.
Based on Steve's recommendations, Michael produced a series of changes
that ended up delivering sane results. In the end, Michael had to lift
some code from the FreeBSD project to address the problem of
converting strings to long longs. This helped the Microsoft compilers
that still had not caught up with the C standard as of the previous
millennium.
party like it's 1999
http://xrl.us/oudw9
http://xrl.us/oudxb
Later on Michael released a newer patch that included all his latest
research on the matter. Steve continued to find a number of rough
edges on Windows. H.Merijn Brand thought that it might be worthwhile
probing for 64-bit variants of time routines on the platforms that
offer them, since that the whole point of the exercise in the first
place. And so he did, and said he'd get around to probing for the
reentrant versions as well.
duty now for the future
http://xrl.us/oudxd
Michael then had a patch working on Windows and Cygwin, contingent on
a couple of details that needed to be resolved. Some problems turned
out to involve the building of "miniperl" itself, which uses some
canned constants before Michael's work is able to work its magic.
Dave Rolsky dropped by to say that he was delighted that all of this
work had a positive effect on the innards of "Time::Local". On the
other hand, it greatly complicated the task of keeping it dual-lifed
on CPAN, so much so that he doubted that the new changes would work
with older perl releases. Michael showed him how this could be done
with some XS goodness.
just in time
http://xrl.us/oudxf
Crash when dying on warning from backticks with vfork() (5.6.1 on Lamp)
Joshua Juran is the caretaker for Perl on the traditional Mac OS (that
is, pre OS/X). Said platform doesn't know how to "fork", but it can
"vfork". In the current state of affairs, asking a program to fork
itself with something silly, like "/dev/null", leads to some very
interesting (read: not useful) results, in that one receives very
little information as to what went wrong.
Joshua managed to get as far as showing how a minor change to
"Perl_do_exec()", "Perl_my_popen()", and "pp_system()" would fix the
problem, but he wasn't sure if his internals-fu was strong enough to
consider all the ramifications.
Nicholas Clark reasoned that the problem Joshua faced was sufficiently
weird (or rather, his platform of choice was weird) that he should
write the tests to establish the desired behaviour out on the end of
the continuum, and then the rest of us could just follow suit.
Apparently he has done this on a code repository hosted on
Sourceforge, but unless I am mistaken they didn't make it to the list.
pneumatic tubes
http://xrl.us/oudxh
http://xrl.us/oudxj
Discussing the (im?)possibility of prototype-based polymorphism for 5.12
David Nicol responded to a previous thread (which I lack the tuits to
track down) with the concept of polymorphism based on prototypes,
which would, amongst other things, make the following work:
sub foo($$);
sub bar(@);
bar foo 1, 2, 3, 4;
# parsed as
bar( foo(1, 2), 3, 4);
He promised to investigate the possibility with his "Macrame" module.
In the meantime, Rafaël Garcia-Suarez reminded David that prototypes
in Perl are more for changing the syntax rather that type inferencing.
http://xrl.us/oudxm
Small incompatibility between 5.8.8 and 5.10.0
Torsten Förtsch discovered a problem that had crept into 5.10, which
appears to be something to do changes to the implementation of
stashes. No-one commented.
something new with ::
http://xrl.us/oudxo
"protochk" and C++
Tony Cook had been puzzled for a while over intermittent smoke
failures when using C++ on Debian, and managed to discover that C++'s
function overloading mechanism was the cause. He suggested a change to
a Configure test, but H.Merijn admitted that it was far outside his
scope of expertise and asked for other eyes to look at it and consider
the ramifications.
looking the other way
http://xrl.us/oudxq
TODO list for moving to git
Nicholas, having endured a painful bisection ordeal under Perforce to
track down when something changed, wondered what was holding up the
migration to git. His current problem was one of mapping a Perforce
revision (a number in a monotonic sequence) to a git checksum.
Mark Mielke wanted to know if there was a page on the web somewhere
that recorded the current status of the Perforce-git migration.
Michael G. Schwern offered an interesting parenthetical remark
regarding the move from Perforce to git, and why it is the Right
Thing. David Golden also noted that git solves the problem of
branching at any point in time, hacking, and folding the changes back
in a most elegant manner. The price you pay, though, is that it is
very hard to point to a specific moment in development (since one only
has an unsortable checksum, not a monotonic sequence).
Craig A. Berry, not fully versed in git-speak, was nonetheless able to
describe how people would communicate points of interest in the
development tree. At the same time, he thought that the barrier to
entry to understanding git was much higher than that of Perforce. As
it turns out, basic web projections of git repositories already come
close to what the All Perl Changes browser provides.
gitting there
http://xrl.us/oudxs
Michael went through the git threads on the list and neatly summarised
them on the Perl5 wiki. He noted with satisfaction that there were no
showstoppers, just a question of tuits.
http://xrl.us/oudxu
"Perl_newSVpvf("%lld")" is broken
One other item that fell out of the Y2038+ code was that, on 32-bit
platforms, "printf("%lld\n", 2**32)" gives a result of -1. Michael and
admitted to being terrified by the code and hoped someone else could
dig down through it and figure out where the problem lay.
quad wrangle
http://xrl.us/oudxw
Pathtools QNX regression
Nicholas Clark looked more closely at Matt Kraai's failures for
5.8.9-tobe on QNX. He determined that it was due to a refactoring of
"File::Spec::Unix::abs2rel" between Pathtools 3.12 and 3.13.
Interestingly, this dredged up an interesting piece of Perl trivia, in
that for a short time, the "/t" flag on a regexp match maintained the
taint flag if the target string was tainted. The idea lived a short
life.
Nicholas thought that creating a new "File::Spec::QNX" (and the like),
since it would be easier to test and would probably simplify the
implementation of "catdir". In any event, he wrote a patch and Matt
confirmed that it fixed up the problem on QNX 6 (a.k.a QNX Neutrino,
or "$^O eq 'nto'").
Ken Williams folded Nicholas's patch into his Pathtools repository.
http://xrl.us/oudxy
git conversion discrepancy
Nicholas Clark uncovered a flaw in Same Vilain's Perforce-git import.
Sam said he'd go over the import code to see if he'd missed anything.
By and large most of the Perforce branches were bit-for-bit perfect.
ancient history
http://xrl.us/oudx2
[EMAIL PROTECTED]
Nicholas produced another snapshot of 5.8.9-tobe. Of note were some
problems on VMS (for which fixes existed) and some minor problems with
"Module::Build".
Slaven Rezic tested some 3700 CPAN distributions and listed a dozen or
so regressions. Most of them turned out to be minor, but one was an
honest to goodness C error, relying on a reallocated SV landing in
exactly right place.
getting closer
http://xrl.us/oudx4
Fedora (Assertion failure on glob assignment)
Nicholas Clark wailed and gnashed his teeth at vendors who insist on
foisting a perl compiled with "-DDEBUGGING" upon their users, and
pondered tweaking things to make it produce a nasty warning on STDERR
during startup.
make it so they have to reboot
http://xrl.us/oudx6
t/op/regexp.t
Abigail wondered how to deal with a test that causes a segfault during
program exit, since even a "fresh_perl_is" from test.pl will return a
correct result, not seeing that $? contains a non-zero value. Michael
G. Schwern thought that the expedient measure of testing $? against
zero should be sufficient.
measuring success
http://xrl.us/oudx8
TODO of the week
A task that need a little sysadmin-type knowledge
Linker specification files
Some platforms mandate that you provide a list of a shared library's
external symbols to the linker, so the core already has the
infrastructure in place to do this for generating shared perl
libraries. My understanding is that the GNU toolchain can accept an
optional linker specification file, and restrict visibility just to
symbols declared in that file. It would be good to extend makedef.pl
to support this format, and to provide a means within "Configure" to
enable it. This would allow Unix users to test that the export list is
correct, and to build a perl that does not pollute the global
namespace with private symbols.
Patches of Interest
Cross-compile for linux
Vadim Konovalov continued to deliver his patches for
cross-compilation. Alas, few people with commit bits have had the time
to review them and enter them into Perforce. There is hope that git
may alleviate these sorts of problems.
http://xrl.us/oudya
http://xrl.us/oudyc
5.8.x on Interix
Ben Morrow reported on the test failures on Interix for 5.8.9-tobe.
Jan Dubois took issue with the skipping of tests, since that might
lead the underlying bugs to be swept under the carpet. Ben thought
that there was a distinction to be made as to whether the test suite
was testing Perl or Perl and its interaction with its host environment
(such as bugs in the C library).
Rafaël hoped that the changes, if they were good enough for 5.8, could
also make it into blead. Ben saw no reason why not, he just wanted to
help get 5.8.9 out the door at the moment.
http://xrl.us/oudye
Invalid read in regdupe in maint-5.8
Nicholas continued to ponder what Vincent Pit had uncovered, regarding
an off-by-one allocation in the regexp compiler.
http://xrl.us/oudyg
New and old bugs from RT
Different behaviour using the "-Idir" option on the command line and
shebang (#6665)
Renée Bäcker wondered why using "-I" on the shebang line of a Perl
program appends the specified directory to @INC, rather than
prepending.
Rafaël Garcia-Suarez explained how and why it was a feature, and Renée
proposed a patch to make "-I" always prepend.
http://xrl.us/oudyi
http://xrl.us/oudyk
"return do { }": take 3 (or 4...) (#38809)
"sub foo { do { return do { 1; 2 } }; 3 }" returns undef. This is
unfortunate. Vincent Pit has been chipping away at the problem, trying
to solve it. This is his latest offering. He's still not happy with
the fix, and suggests that it's either this, or ignore the bug.
tests will tell
http://xrl.us/oudyn
Perl 5.8.8 Build Failures for SunOS 4.1.3 (#59456)
Bob Peterson called for help in getting a new Perl running on a very,
very long in tooth SunOS platform. Andy Dougherty thought that the
last time he had attempted such a task was in 2001, and thought that
some of the errors Bob was encountering were due compiler bugs, and
that building without "-O2" optimisation may alleviate some of the
problems.
Nicholas Clark identified some failures as being Mostly Harmless, but
others were rather more disconcerting.
teaching an old dog
http://xrl.us/oudyp
http://xrl.us/oudyr
"Unicode::UCD::casefold()" does not work as documented, nor probably as
intended (#58430)
Karl Williamson continued to work on Perl's simple-minded
implementation of folding case for Unicode characters, the real-world
problems that this induces, and a proposal on how to move to something
that works whilst retaining backwards compatibility.
Rafaël asked for some background for the readers following along at
home, and Karl responded with a very well written summary of the
problem domain.
all you need to know
http://xrl.us/oudyt
Segfault on weird but plain Perl in eval on 5.10.0 on Windows (#59498)
Eirik Hanssen and Alexandr Ciornii pinned down some code that failed
in Strawberry Perl 5.10.0 and wondered if it was common to all Windows
5.10 builds. Cygwin and Unix builds appeared to be unaffected.
broken windows
http://xrl.us/oudyv
Memory leak with regex in 5.10.0 (#59516)
Robin Hill offered an interesting bug on 5.10 that proceeded to eat
all memory. The trigger was a regexp with a quotemeta'ed portion and
some single character character classes.
Nicholas Clark noted that while lots of memory gets chewed up, if the
program is able to run to completion, every last byte is correctly
freed. Dave Mitchell produced a smaller test case to demonstrate the
leak... which still cleaned up after itself if things ended in an
orderly fashion. Believed (by Nicholas) to be solved.
http://xrl.us/oudyx
Surprising behaviour when "$" is left off $last (#59522)
Inside a curly brace block, even just for lexical scoping, "last" will
take you out of it without a murmur, even if you write "$x < last"
instead of "$x < $last". Unfortunately there's not a whole lot that
can be done about it.
http://xrl.us/oudyz
"readline" returns EBADF at eof in 5.10.0 (#59550)
Mark Martinec reported that the "readline()" function (or a diamond
I/O operator "<>") returns a EBADF (Bad file descriptor) as its errno
status on end-of-file when PERLIO is set to "stdio".
http://xrl.us/oudy3
Error installing a Perl 5.8.8 (#59610)
Leandro Gregorio needs some help with an installation on a 64-bit
Linux platform.
http://xrl.us/oudy5
FOLDCHAR regop not produced for "\x", "\0", "\N{U+....}" (#59616)
Karl Williamson is now using the latest version of blead for his work
and is pushing out the bugs he encounters in Unicode case folding. His
latest item is that specifying characters in hex, octal or named
characters defeats the regular expression engine.
http://xrl.us/oudy7
Save code generated by references in @INC (#59626)
Shawn Moore wanted to be able to profile code references in @INC via
"Devel::NYTProf", and found a number of hurdles in his way. He offered
a patch that appeared to work, but Nicholas Clark pointed out that it
did in fact only appear to work, and making it work would in fact be
much more difficult.
http://xrl.us/oudy9
Unicode problem (#58182)
Karl Williamson continued on his Unicode trek this fortnight, with a
summary of the issues concerning this bug (for which the main point is
about how to land it gracefully in 5.10 in a backwards-compatible
manner, switchable via a lexical pragma). Another item is what to do
about regular expressions which are compiled in one (Unicode-encoding)
context and then used in another.
Glenn Linderman and Rafaël made a few comments, and it appears that
Karl has managed to reach a concensus of sorts.
http://xrl.us/oudzb
"unicore/mktables" expects wrong syntax from CaseFolding.txt for Turkish
(#58656)
Karl pinned down the bug in Turkic character handling in Unicode. In
his words: "it appears that the Unicode folks decided they were doing
the wrong thing in 3.1, and changed it in 3.2. Perl is still looking
for the 3.1 syntax." That is, they snuck it in without telling
anybody. Karl hopes to be able to produce a patch.
http://xrl.us/oudzd
"File::Copy" does not handle file objects sanely (#59650)
Wow, another bug in "File::Copy".
http://xrl.us/oudzf
Too late for -CS option (#59652)
Either that, or too early, since no-one has the tuits to implement
something that would do the right thing. In the meantime, Aristotle
Pagaltzis proffered the canonical workaround.
http://xrl.us/oudzh
SIGSEGV compiling regexp in 5.10.0 (#59654)
Salvador Fandiño found a way to make things go boom. But what could
that pattern be used to match?
6000 parens is not enough
http://xrl.us/oudzj
"Cwd::realpath" fails on unsearchable directory (AIX) (#59662)
John Wiersba showed that a short C program worked where Perl fell over
and choked.
just need to cut'n'paste
http://xrl.us/oudzm
Segfault when using "(?|)" in regexp. (#59734)
Abigail gives the regexp engine indigestion, with a short, sharp "perl
-wE '";" =~ /(?<a>(?|(?<b>;)))/;'" to the ribs.
new toys broken
http://xrl.us/oudzo
Documentation issues with 5.8.8/Math/BigInt.pm (#59746)
Paging Tels. White courtesy phone.
unless fixed in blead?
http://xrl.us/oudzq
"File::Find" behaviour with files among @DIRS (#59750)
J. Flack noted with pleasure that "File::Find" does more or less the
right thing when given a file as a starting point. And in fact, if it
didn't, it would be incredibly awkward to make it so from the client
side.
Unfortunately, it is completely undocumented, so his/her plea was to
have it documented so that it could be relied on, unless perchance it
doesn't work at all on some obscure platform.
when you need it, you need it bad
http://xrl.us/oudzs
Changing effective userid from root to normal user fails on Linux (#59766)
Markus Huaraz filed a bug report on Linux regarding the setting of $>
preventing perl from reading its own binary. The "/proc" symbol table
entered the picture, but Rafaël Garcia-Suarez was unable to reproduce
the problem.
note to self
http://xrl.us/oudzu
Not OK: perl 5.11.0 +DEVEL +patchaperlup: on i686-linux-64int
2.6.22-1-k7 (UNINSTALLED) (#59776)
Andreas König reported a smoke failure and suggested the fix (in
"ExtUtils::MakeMaker").
http://xrl.us/oudzw
Cannot recurse inside (?|) (#59792)
Whilst working upon the next release of "Regexp::Common", Abigail
encountered some flaws in the implementation of "(?|)" and offered
some tests to pin down the problem.
broke again
http://xrl.us/oudzy
Hash collision? (#59796)
Nope, just symbolic references that "use strict" would have caught.
priceless
http://xrl.us/oudz2
"return 0 or die" (#59802)
return doit() or die "did it wrong";
It would be nice if that warned "unreachable statement".
that or Perl::Critic
http://xrl.us/oudz4
Perl5 Bug Summary
279 new + 1054 open = 1333 (+15 -5)
http://xrl.us/oudz6
http://rt.perl.org/rt3/NoAuth/perl5/Overview.html
New Core Modules
Module::Build 0.30
http://xrl.us/oudz8
http://xrl.us/oud2a
ExtUtils::MakeMaker 6.46
http://xrl.us/oud2c
IPC::Cmd 0.42
http://xrl.us/oud2e
File::Fetch 0.16
http://xrl.us/oud2g
Archive::Extract 0.28
http://xrl.us/oud2i
In Brief
Renée Bäcker pointed out that there are many patches in RT bug
reports, just begging to be applied.
http://xrl.us/oud2k
http://xrl.us/oud2n
Michael G. Schwern suggested an improved "GM/LOCALTIME_MAX/MIN" search
algorithm. H. Merijn Brand suggested a tweak or two.
http://xrl.us/oud2p
Jim Cromie was stung by list context in assignment.
bad luck
http://xrl.us/oud2r
Michael G. Schwern discovered that HP's Testdrive being replaced. As a
long-time resource for testing VMS issues regarding Perl, it will be
greatly missed. The HP engineer that H.Merijn contacted suggested that
something could be worked out.
thanks for all the fish
http://xrl.us/oud2t
Nicholas Clark wasn't sure if CPAN bug #39403 involved something that
needed to be fixed in the core (the ability to overload or intercept
an attribute, other than using a source filter).
http://xrl.us/oud2v
Nicholas also proposed a wild-assed guess to allow parallel testing on
Win32 but Steve Hay reported no joy. Andy Armstrong understood the
resulting symptoms sufficiently to volunteer to see if he could figure
out why.
http://xrl.us/oud2x
Salvador Fandiño noted that Paul Fenwick was not the first person to
whether the prototype for "CORE::truncate" is wrong.
http://xrl.us/oud2z
Nicholas removed the missing type "VSTRING" in the documentation to
"ref" since it wasn't supposed to be there at all, being an overly
optimistic backport from blead.
bug #59264 solved
http://xrl.us/oud23
John O'Rourke ran into some odd behaviour of "substr(lc($utf8))" in
5.8.8 that Nicholas had fixed, he thought, thanks to a TPF grant.
Since that work had made it to 5.10 and had been backported to the
upcoming 5.8.9, he was happy to leave things there.
http://xrl.us/oud25
Nicholas noticed some "make distclean" failures, in that there were
some files left over from a run of the test suite that weren't cleanup
up after the target was run. Andy Armstrong began to look at cleaning
things up, since he had a nagging suspicion that a number of them
might be his fault.
http://xrl.us/oud27
H.Merijn Brand released "Data::Peek" to CPAN.
a collection of low-level debug facilities
http://xrl.us/oud29
Nicholas saw a Debugger saved lines regression and wondered out loud
what was the new officially sanctioned way of noting new subroutines
that are defined during an "eval". When the right technique is found,
a test he wrote should begin to pass.
http://xrl.us/oud3b
If Dave Mitchell is ignoring *you*, resend your message.
the tale of davem's lost emails
http://xrl.us/oud3d
Last week's summary
This Week on perl5-porters - 15-21 September 2008
http://xrl.us/oud3f
About this summary
This summary was written by David Landgren.
Weekly summaries are published on http://use.perl.org/ and posted on a
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archive is at http://dev.perl.org/perl5/list-summaries/. Corrections
and comments are welcome.
If you found this summary useful, please consider contributing to the
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--
stubborn tiny lights vs. clustering darkness forever ok?
