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This Week on perl5-porters (17-23 April 2006)

David Landgren
April 26, 2006 05:30
This Week on perl5-porters (17-23 April 2006)
Message ID:
This Week on perl5-porters - 17-23 April 2006

Topics of Interest

Redoing the regular expression API

   Yitzchak Scott-Thoennes suggested that Yves Orton send in a patch to
   pull out some of the ancillary functions in "Data::Dump::Streamer" in
   order to make them available in the core distribution.

   So Yves did just that. The first addition is to add "reftype_name()",
   that behaves like "reftype" except that it returns false rather than
   "undef" on non-references. This removes the need for fussy make-work
   code on the client side to avoid warnings.

   The second addition is a "regex()" function, which makes it easier to
   deal with patterns, whether they have been blessed into other
   namespaces or not.

   Graham Barr admitted that the return value of "reftype()" was a
   mistake, and "reftype_name()" was acceptable, but felt that the
   "regex()" function was better off in the "Regexp" module.

   Yves didn't like the fact that "Scalar::Util::reftype" returns
   "SCALAR" instead of something like "REGEX". Nick Ing-Simmons liked the
   idea, but thought that it was too dangerous for "maint".

   Another sub-thread in the discussion revolved around whether a qr//
   thing is an object or a type. It is, in fact, an object, but Yves
   argued that it is much more useful to treat it as a type. Graham
   agreed to disagree.

   Adam Kennedy admitted to using "Regexp"s as objects quite a bit and
   would be happy to see the "Regexp" module receive a dose of
   spring-cleaning (which I suppose means fixing up the reblessing
   inconsistency that Yves was getting at).

   Another hassle Yves pointed out was the non-reversibility of
   stringifying regexps:

     my $qr=qr/foo/;
     my $str="$qr";
     print qr/$str/; # equivalent but not equal

   Dave Mitchell pointed out that a regular expression currently *is* a
   scalar, it just happens to have a bit of magic attached...

     Shouldering the weight of history

Silly regexp tricks

   Hugo van der Sanden returned to the super-linear cache bug (a "||"
   logical or instead of a "|" bitwise or) in the regular expression
   engine, and came up with a suitable test case:

     ("a" x 31) =~ /^(a*?)(?!(a{6}|a{5})*$)/;
     print length($1);

   This prompted Yitzchak Scott-Thoennes to come up with another bug that
   showed how "blead" broke existing behaviour. Since no-one should ever
   have come to rely on this behaviour, it was all quietly swept under
   the rug. Dave Mitchell hinted that he was working on New Stuff in the

Bringing "threads" into the third millenium

   Jerry D. Hedden continued to send patches to sync CPAN's "thread"s
   with "blead", first by removing a superfluous counter.

     and again

     and reworked the threads destruct call

   He vented his frustration at the slow pace with which the patches were
   getting applied, believing that he was playing by the rules as much as
   possible. Rafael was very apologetic, explaining that he understands
   so little about threads that he's barely qualified to apply them. And
   apart from Rafael, there aren't too many alternatives.

Backporting the new "blead" RE improvements to "maint"

   Nicholas Clark posted a proof-of-concept update to to deliver
   Dave Mitchell's iterative (as opposed to recursive) implementation of
   the regular expression to perl 5.8.1 and beyond. A few show-stoppers
   need to be cleaned up: some coredumps in the test suite need to be
   sorted out and some tweaks to ppport.h are needed. As a bonus, Yves
   Orton's trie work comes along for the ride.

     More songs about building regexps

"valgrind" and Perl 5

   Nicholas Clark wondered what would happen, as in, how many bugs would
   be uncovered, if one were to run the test suite under "valgrind". So
   Rafael Garcia-Suarez did just that, and discovered that 41 test files
   produce errors.

   Nicholas and Rafael then set about fixing up the problems that were

     There's always something to do

Better reporting of TODO tests

   Nicholas Clark looked at the unexpurgated version of the output from
   the test suite and noticed that six tests were marked as unexpectedly
   succeeding. In test parlance, these tests are called TODO tests, since
   they show what there is to do. This state of affairs is usually due to
   a test case that is expected to fail when run, since it exercised a
   bug in perl that needed to be fixed, and at some point, a source code
   change caused the failing test to succeed.

   Nicholas saw that many of the really old regexp bugs that have been
   fixed, had no TODO tests, and in any event, the default, summarised,
   output of the test test suite makes no mention of them anyway, so it
   is not as if anyone would have noticed the improvement.

   So firstly, the test harness had to be upgraded to report the summary
   of TODO tests that succeed, and (much more work) all the open bugs
   need test cases written for them, so that it becomes easier to see
   when they have been fixed.

   Yves Orton hacked up his copy of "Test::Harness" to do this. Andy
   Lester took the idea and applied it to his development version of
   "Test::Harness" (see the "New Modules" section below).

   Abe Timmerman updated the test smoke kit, in order to get all this new
   goodness into the hands of the smokers.

     Much ado about todo

     Up in smoke
     rsync -avz .

Coverity coverage of CPAN modules

   After having read the traffic on p5p concerning the errors that
   Coverity uncovered, Alan Olsen what the possibilities were for having
   the tests extended to cover CPAN modules with XS components.

   Johnathon Stowe realised that it was the output of "xsubpp" that needs
   to be tested, rather than the ".xs" files themselves, and wondered
   whether all the possible constructs it is possible to have "xsubpp"
   emit ere in fact being covered, and whether one ought to create a
   dummy XS module that simply causes "xsubpp" to emit everything it
   knows how to.

   Tim Jenness thought that that issue should be covered by
   "XS::Typemap". Johnathon did some quick coverage calculations and was
   surprised to learn that it wasn't too shabby.

   Andy Lester volunteered to liaise with the Coverity people to have
   XS-based modules analysed, should the authors in question care to know
   the results. Randy W. Sims was concerned that some authors might think
   of it as a ratings system. Be that as it may, a couple of authors
   asked for analysis to be applied to their modules.

Patches of Interest

   This week, Andy Lester performed some more "op_type" shrinking in sv.c
   and dump.c,

   and hauled some variables down into tighter scopes in util.c.

212 warnings emitted by gcc-4.2

   Marcus Holland-Moritz grew tired of watching an endless list of
   warnings spew from compiling perl with a recent copy of "gcc", so he
   patched things to get rid of the problems that gave rise to them.

   Andy Lester was pleased to hear of the work, since it had been
   something of an annoyance for him too. He asked for a slightly less
   monolithic patch, so that different classes of errors could be fixed a
   bit at a time. Rafael eventually applied all the changes.

     Understanding error messages

Watching the smoke signals

   Nicholas Clark looked at a NetBSD smoke report, and wondered what it
   was that was being tested in ext/B/t/bytecode.t that was failing.
   Whatever it was, he fixed it with change #27874.

     Smoke [5.9.4] 27855 FAIL(F) netbsd 3.0 (i386/1 cpu)

   Steve Peters wondered why a test run was failing, simply because TEST
   was seeing test results being delivered out of order, where as harness
   didn't care.

     Smoke [5.9.4] 27939 FAIL(F) MSWin32 WinXP/.Net SP2 (x86/2 cpu)

New and old bugs from RT

op/cmp.t and lib/bigfltpm failures (#5708)

   Steve Peters and Johnathon Stowe kicked this bug around, but as
   neither of them have access to the platform in question it shall have
   to remain open for the time being.

     OpenServer anyone?

Regex replace loses characters (#24704)

   Rafael fixed this bug by accident while working on something else.
   No-one minded.

   In fact, Steve Peters continued his thankless task of trawling through
   old, open tickets and noticed that a certain number of bugs had been
   solved by changes committed recently and not so recently.

     Fixed in previous millenium

"Sys::Syslog)"  requires \0 terminator in syslog messages (#28019)

   Julian Mehnle called in from Debian-land to see what the status on
   this bug was, explaining that some comments or documentation would
   help avoid bugs being filed in the future.

"threads" and "require IO" causes segmentation fault (#37076)

   Nicholas Clark jotted down a couple of notes on how to fix this

     Add it to the TODO

Oxymoronic example in perlvar (#38743)

   Steve Peters wondered why Dave's excellent example shouldn't be used
   to close this ticket.

"Text::ParseWords" doesn't always handle backslashes correctly (#38904)

   John Vromans argued that the following equivalency was incorrect:

     is_deeply([shellwords("aa bb cc\\ ")], ["aa", "bb", "cc "])

   Alexey Toptygin delved into the code to find out why and offered a
   patch to make the behaviour a little more intuitive. Applied by

"map" sometimes uses only the last mapped value (#38935)

   Someone on Perlmonks posted an innocuous question about some strange
   behaviour with "map", that turned out to be a caused by a change that
   was applied in 1998. People were surprised at that such a bug had
   remained unnoticed for so long.

     The original thread

"Configure" won't handle versions 5.10.0 or 5.8.10. (#38945)

   Andy Dougherty filed a bug on this problem so that people remember to
   do something about it in time.

Memory leak when calling "system 1 foo" repeatedly (#38946)

   An interesting discussion arose from this report. It turns out that
   "system 1, ..." does something interesting under Windows.

Tests fail in 5.8.8 if $TMP is not writable (#38947)

   Gabor Szabo noted that certain tests lib/Memoize/t/tie_ndbm.t fail if
   the directory pointed to by $TMP was not writable. He felt that a
   diagnostic should explain more clearly what the problem is rather than
   failing out of hand.

Migration Problem from Dynix to Aix (#38951)

   Karuppiah Subramaniam has a migration problem. If you have any advice
   to offer, I'm sure it will be appreciated.

"exists" error message on wrong argument type is incorrect (#38955)

   Jeremy Hetzler wished to clarify the error message received when
   "exists" use incorrectly, and bring it into line with the

"File::Find" documentation - is "Don't modify these variables" still 
valid? (#38965)

   Steve Peters tweaked the documentation for "File::Find" to specify
   more clearly what happens to $_ in the callback routine.

Perl5 Bug Summary

     9 created and 4 closed = 1543

     Steady as she goes

New Core Modules

   *       Test-Harness version 2.57_06, by Andy Lester. This enhances
           the summary result to indicate clearly the number of TODO test
           that have unexpectedly begun to succeed, (usually due to
           underlying bugs being fixed).


In Brief

   Nicholas Clark carried out his threat to document code references in
   @INC and source filters and also added a new feature at the same time.

   Paul Johnson read about the "is_list_assignment" speedup patch from
   Andy Lester, and pointed the porters to a two year old thread on a
   similar issue.

   Nick Ing-Simmons followed up on the issue of leaking file handles in
   XS code.

   Jan Dubois removed some cruft from

   Jarkko Hietaniemi tried a patch to regcomp.c to see if it would
   silence an error from Coverity. It didn't. This led Jarkko to conclude
   that if Coverity was too clever, or too stupid, to figure out what was
   really happening, then maybe it's Red-flag-for-Refactoring time.

     It would help us, frail humans

   He then nailed another leak that Coverity found in doop.c.

   Nicholas Clark saw that Coverity dislikes "PerlIO_findFILE". The logic
   seems a bit tortuous, so maybe that's not so surprising,

   Nicholas looked at the last two unreviewed Coverity issues, in
   regexec.c and wondered whether Coverity was getting confused. Dave
   Mitchell explained that both issues were false positives.

   Alex Waugh provided the required information to support compiling perl
   on RISC OS.

   Andy Lester posted a short script to prune Jarkko's "cpd" output, to
   show more clearly where Cut-And-Paste code was happening in areas that
   interested him.

   Yitzchak Scott-Thoennes fixed building perl on "Cygwin".

   Joshua Juran uploaded an experimental release of Lamp on SourceForge.

     Lamp Ain't Mac POSIX

   Andy Lester refactored the excessive use of "PM_GETRE()" in pp_ctl.c.

   Jan Dubois and Steve Hay coordinated the ActiveState changes to
   win32/Makefile in "blead", clearing up an issue concerning 64-bit
   environments at the same time

   Nicholas Clark explained what he understood Larry's MAD patch to be

   The UTF-8 caching code that Nicholas Clark worked on a few months back
   wound up being exposed on the command-line via the "-Ca" switch.

     Unless someone has a better idea

   Nicholas Clark unearthed what is in hindsight a blindingly obvious
   memory leak on unthreaded builds between "Perl_newCONSTSUB" and

     Nobody else knew what to do about it, either.

   Andy Lester thought that "GvUNIQUE()" and its ilk could be removed
   from the source. Rafael commented that the macros had to remain, since
   at least "Data::Alias" on CPAN refer to them.

   Ashish Agarwal was having problems with weird characters displayed in
   the debugger. Joe McGuire thought it was probably one of the thirteen
   so-called variant characters in EBCDIC.

     \ [ ] { } ^ ~ ! # | $ @ `

   Andy Lester cleaned up regexec.c following on from the recent changes.

   Rick Delaney had discovered that lost their compile-time
   benefit, dating back to when pseudo-hashes were removed from "blead".

   Ken Williams asked for advice on some proposed "File::Spec" changes
   for VMS, John E. Malmberg supplied what information he could. Ken
   lamented how difficult it was to test VMS code if you didn't have
   access to a VMS box.

   Joshua ben Jore thought that the terribly cryptic
   "select((select(OUTPUT_HANDLE), $| = 1)[0])" idiom should be banished
   from the documentation. Rafael bowed to reason.

     Just because you can

The previous summary

   The cynics scoffed at the effort expended to clear the Coverity
   issues, and Rafael pointed out that "state" variables are almost but
   not quite yet in "blead".

About this summary

   This summary was written by David Landgren.

   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:

   Weekly summaries are published on and posted on a
   mailing list, (subscription: The
   archive is at Corrections
   and comments are welcome.

   If you found this summary useful or enjoyable, please consider
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