This Week on perl5-porters - 27 February-5 March 2006
"Module::Build" achieves core status, VMS improvements, and the usual bunch of bug fixes and enhancements. Topics of Interest Function prototyping and op/utftaint.t failures in "blead" in "Win32" Yves Orton first starting looking at smoke failures on Win32, and wondered why he was seeing redefined subroutines in "Getopt::Long", but Nicholas Clark stepped up and said that Yves had been caught out by a glitch that had since been fixed in the source code. Steve Hay and Nicholas worked through the failure, which was a problem of taintedness when "." (dot) appears in the "PATH" environment variable. A fine example of how hard it is to get cross-platform platform-dependent code correct. http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/2006-02/msg00939.html "Term::ReadLine", "CON:" and "Term::ReadKey" on "Win32" (cpan #17773) Johnathon Stowe mentioned the issues he had uncovered with CPAN bug reports filed against "Term::ReadKey". He had traced the problem to "Term::ReadLine" using the special device "CON:" (as in *console*) on "Win32". One may open such a file directly, and things will work correctly, but open the file and pass it as a handle to "Term::ReadLine" and things start to fall apart, which is in fact what happens at the moment. Johnathon thought that the best approach would be to fix "Term::ReadLine". Somebody else's bug http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/2006-02/msg01018.html DBD::Oracle 1.17 and 64-bit perl on AIX 5.1 John L. Allen was failing miserably at getting Oracle and 64-bit perl on AIX to talk to each other, and asked for help. H.Merijn Brand thought that the combination was "like voluntarily having someone tie you down on a bed of nails, and then being whipped with a bunch of rusty barbed wire." Dave Mitchell considered it highly doubtful that one would be able to connect a 32-bit Oracle library to a 64-bit perl. After trying out different long integer and long double Perl compilations, John succeeded in building a perl with 32-bit integers, long doubles (128 bits) and Oracle all playing nicely. Alan Olsen, speaking from experience, recommended that John go either full 32-bit, or full 64-bit. Choosing the middle ground just leads to pain and unhappiness. It can be done http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/2006-03/msg00008.html "pow" failures on AIX with "uselongdouble" After having done battle with Oracle on AIX, John L. Allen turned his attention to failures in the test suite, and noticed some misbehaviour with the "pow" function. Dominic Dunlop confirmed that something strange was indeed occurring. After a bit of detective work, John realised that the problem was not with perl, but AIX's underlying math libraries. He wrote a small C program to demonstrate the error, which should allow someone with the necessary "Configure"-fu to write the probe to work around the breakage. The library and the damage done http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/2006-03/msg00105.html Detecting @ISA cache invalidation Caching in which package a method is found ensures decent run-time performance. That is, if an object calls a method unknown to the current package, it consults @ISA to look for other packages that may have a suitable method. Once it succeeds in finding it the first time, it caches the information so that subsequent method calls can avoid paying the cost of the search. That works fine until @ISA is modified, in which case the cache has to be invalidated, which in turn means that objects need to take a fresh look through the @ISA chain to locate their methods again. Usually you don't have to care about this at all, it just works. But some modules extremely tricky things, and can get thrown by changes to @ISA, and worse, up until now there was no easy way of determining when it happens. So Joshua ben Jore wrote "B::sub_generation", which provides a handy technique for letting user code know when cache invalidation occurs. When asked to explain what this all meant, Joshua provided a short snippet of code, showing how things can get derailed if code doesn't realise that @ISA changed. Rafael thought that Joshua's exposé should be saved somewhere in "perlguts". Talkin' about my B::sub_generation http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/2006-03/msg00021.html Small bug fixed in "Module::Build" passthrough Makefile.PL Ken Williams made a change to "Module::Build::Compat" to deal with the fact that the method call "CPAN::Shell->install()" doesn't appear to return anything useful. Yitzchak Scott-Thoennes wanted to know how one could reliably test to see whether the install did in fact succeed. Andreas Koenig recommended using the "$module->uptodate" method as a suitable work-around. Ken planned to use that approach soon. Look for a new version of Module::Build soon http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/2006-03/msg00031.html Tracking down leaks in "XS" "SV"s Tracking down leaking scalars in "XS" code is hard. Andy Armstrong has started to work on "Devel::LeakTrace", which uses a custom run loop, and was having trouble determining the relationship between where "SV"s are created, and where perl reports that they were created. Dave Mitchell pointed out that since 5.8.1 it has been possible to compile a perl executable with "-DDEBUG_LEAKING_SCALARS", which adds extra information to "SV"s, which in turn can be picked up by something like "Devel::Peek". On the other hand, Andy's approach has the benefit of not requiring a specially prepared perl. http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/2006-03/msg00066.html http://search.cpan.org/dist/Devel-LeakTrace/ Understanding "ext" and testing Adam Kennedy is working on the Vanilla Perl 5.8.8 distribution, and was having trouble with some of the tests in the "IO::" packages. He didn't understand how the tests could succeed at all, and wondered how long they had been failing. Steve Hay had a look, and saw that the behaviour is dependent on whether the "fork" emulation code is used or not. And that some of the tests to see whether "fork" is defined or not are quite bizarre. Nick Ing-Simmons came to the rescue, giving an explanation for why some of the things are the way they are. All in all, it's an area that Needs Work. http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/2006-03/msg00078.html Making "File::Find" Iterative The venerable "File::Find" module uses a callback scheme, something beginners to Perl may find a bit unusual. Shlomi Fish looked at extending it to provide an iterative interface similar to Shlomi's own "File::FTS" module. Randal Schwartz pointed to an article he had written that dealt with the same issue. Steve Peters noted that the main criterion for judging patches to "File::Find" is that they should incur no speed penalty, thus, for a patch to be accepted, it would need solid benchmarking. Nick Ing-Simmons explained that the question of speed was one of system calls. Make one unnecessary call, and the difference would show up for people scanning deep and wide directory trees. In the end, Shlomi decided to concentrate on "File::Find::Object", as it appeared to be closer to suiting his needs. David Nicol wondered whether "File::Find" was thread-safe, and Tels made a plug for his own "File::Walker" http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/2006-03/msg00047.html File::FTS http://search.cpan.org/dist/File-FTS/ File::Walker http://search.cpan.org/dist/File-Walker/ Will someone please fix "Devel::DProf"? Jarkko Hietaniemi made a plea for someone with too much spare time on their hands to please take a look at "Devel::DProf" and fix some its worst bugs. Andy Lester wanted some test cases. Jarkko countered with: $ perl -d:DProf -e 'sub foo { next } for (1) { foo }' $ perl -d:DProf -e 'use autouse qw(Pod::Usage pod2usage); pod2usage' Tels searched the RT queue: http://rt.perl.org/rt3/Ticket/Display.html?id=24058 The bug stops here http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/2006-03/msg00152.html "Module::Build" 0.27_08 added to the standard distribution A first attempt was made to add "Module::Build" to the core. This was perhaps the largest thread of the week. It appears the graft has succeeded, but more work is required. http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/2006-03/msg00167.html The continuing saga of "*a=$a=*b;${"a"}=*a;" Nicholas returned to the "*a=$a=*b;${"a"}=*a;"-perl-go-boom bug and couldn't see a easy way out, short of cheating and getting the optimiser to spot the sequence and thereby emit a different op-tree to make the problem go away. David Nicol wondered whether it was a case of worrying too much about a construct that doesn't come up in practice. chromatic thought that a tool simply should not crash on invalid input. http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/2006-03/msg00169.html Some more VMS goodness Peter Prymmer sent in a patch for some VMS-specific issues, which Craig Berry applied partially. Peter was lacking a bit of context to understand the reason why Craig did not apply the rest of it, and John E. Malmberg summarised the issue nicely for the vmsperl readership who don't follow p5p, and thus also saved the p5p summariser from having to do so: Peter's patch http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/2006-03/msg00170.html John's summary http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/2006-03/msg00186.html Matching dynamic Unicode properties Dan "Mr. Encode" Kogai related something he'd heard about non-existent Unicode properties (like "\p{IsBogus}") in pattern matches. Sometimes perl spits out an error... but not always. Yitzchak was quick to that the results depended on whether the match had failed or not before the scanner reached the location of "\p" property in the target string. Hugo van der Sanden wasn't even sure one could call it a bug (which Dan did not say either), but thought that perhaps the "utf8" module could offer something to check for this situation, since, as Sadahiro-san pointed out, it could be hard to check for user-defined properties sufficiently early in the general case. http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/2006-03/msg00189.html What Andy Lester did this week Removed a redundant o->op_type http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/2006-02/msg01001.html http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/2006-03/msg00000.html Non-null optimizations for SvREFCNT_inc http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/2006-03/msg00032.html Initialising all of mgvtbl http://www.xray.mpe.mpg.de/maIling-lists/perl5-porters/2006-03/msg00033.html Patches of Interest "PERL_TRACK_MEMPOOL" cripples environment after "exit()" Marcus Holland-Moritz uses "blead" for his daily work, which leads to some interesting discoveries. He had wanted to run "gcov" coverage analysis of one of his XS modules, and became distracted by strange failures, probably best attributed to the environment variable code clean out that took place a few months ago. Evidently there are still demons lurking in that code. Marcus supplied a patch to nail one of them, applied by Rafael Garcia-Suarez. http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/2006-02/msg00940.html Silence useless errors in "B::Lint" for "grep" Joshua ben Jore offered a patch to silent what he perceived to be a useless warning emitted by "B::Lint", concerning implicit matches with "grep". Since "grep{ /pattern/ }" is such a frequent idiom (and insofar as $_ is topicalised (the New way of referring to what used to be known as "local"ised) within the "grep" code block), it's a rather stupid warning. Rafael agreed with Joshua and applied the patch, saying that he'd be happy to accept similar patches for postfix "for" and "map". http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/2006-03/msg00002.html Long pathnames on VMS and sundry fixes John E. Malmberg sent in a patch for VMS builds and long pathname handling. Abe Timmerman reported that results looked good. The patch http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/2006-03/msg00122.html The smoke results http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/2006-03/msg00127.html Watching the smoke signals Smoke [5.9.4] 27358 FAIL(F) hp-ux 11.11/64 (PA-2.0/64/2 cpu) H.Merijn Brand poked around in "test.pl" to try and cope with change #27345 and problems with tainting. He made the appropriate changes to get things to work on HP-UX but wondered whether the patch would work on other systems like "VMS" or "Win32". Steve Hay found problems with the latter, and proposed an alternative. http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/2006-03/msg00041.html New and old bugs from RT Lexical variables in regexp "?{}" assertions (#38639) Richard Clayton identified a problem with lexicals defined within a "for" and being set within a "?{}" assertion of a pattern match. It gets set the first time through the loop, but not on subsequent iterations. The work-around is to declare the lexical in a scope further out from the "for" block. No takers. http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/2006-02/msg00941.html "Configure -des" stops waiting for "<CR>" (#38642) Anton Koinov ran into problems configuring perl on Gentoo. Andy Dougherty was intrigued, and tried to guess what was going wrong, and suggested Anton run the following command sh -x ./Configure -S 2>&1 | tee Configure.out ... in order to capture all of the text generated during the run (as "-des" discards certain output deemed to be mostly harmless). No news back from Anton as of yet. http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/2006-02/msg00944.html MULTICALL causes segfaults with very large return stacks (#38644) Tassilo von Parseval has been working with the new "MULTICALL" interface and noticed problems when the return stack is very large. This shows up as segfaults in XS code, such as "List::Util". http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/2006-02/msg00958.html Long file names on Stratus VOS (#38645 and #38646) Paul Green uses Perl on Stratus VOS, whose file system limits file names to no more than 32 characters. This poses a problem when he tries to run the test suite of a module like "Pod::Simple", which contains a test name search_25_glob_squaa_coloncolon_kleene.t. At 40 characters long, that's more than Stratus can bear. Similarly, there's another file, _white_with_navy_blue_on_black.css that is also a bit too long. Nicholas Clark wondered whether 32 was some sort of POSIX minimum, and recalled that some tests had already been renamed to deal with characters in file names that VMS had trouble processing. Joshua Juran noted that traditional Mac-based platforms ("MacOS" and "Lamp") are limited to 31 characters. (MacOS X does not have this limitation). (The Summariser wishes to point out the existence of Sébastien Aperghis-Tramoni's "Test::Portablility::Files" to module authors). One file http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/2006-02/msg01003.html And then another http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/2006-02/msg01004.html No more excuses http://search.cpan.org/dist/Test-Portability-Files/ 64-bit (non-)builds on Solaris 8 (#38664) James Overly had problems building a 64-bit perl on Solaris 8. http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/2006-03/msg00058.html Debugger Loses Names for Anonymous Subroutines (#38673) chromatic showed how the trick of assigning to the "__ANON__" typeglob to name an anonymous subroutine doesn't work in the debugger. http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/2006-03/msg00147.html "O::Deparse" not working as expected (#38684) "harleypig" was having trouble with "split". I tried to pay attention, but Stephen McCamant supplied a patch to fix the behaviour (which was apparently broken), which was applied by Rafael. The end. http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/2006-03/msg00202.html Perl5 Bug Summary 1548 open items http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/2006-03/msg00193.html in all their glory http://rt.perl.org/rt3/NoAuth/perl5/Overview.html New Core Modules * "CPAN" version 1.87 uploaded by Andreas Koenig. http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/2006-02/msg00949.html * "Archive::Tar" version 1.29 uploaded by Jos I. Boumans. http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/2006-03/msg00074.html In Brief Seung-Ho Han wanted to know how make sense of what "B::Xref::compile" produces. Joshua ben Jore explained what was going on, and that more clues can be found by studying O.pm. http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/2006-02/msg00952.html Jerry Hedden started to extract threads.pm from the core in order to make it available on CPAN. This would permit enhancements to be made to the threads implementation faster than the current "blead" to "maint" to "release" cycle. http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/2006-02/msg01013.html Jim Cromie continued to refine his self-described hare-brained "op-next"/"op-sibling"optimisation scheme, defending it against the critics, but ran into trouble somewhere deep down in the guts. In doing so, he came up with a new presentation scheme for "B::Concise". http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/2006-03/msg00001.html Anton Berezin caught and eliminated an extraneous "#endif" in fakesdio.h. http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/2006-03/msg00010.html Jarkko Hietaniemi discovered that "-d:Foo=bar" no longer works in the current Perl release (bug report #38657). Rafael traced the problem down to the fact that "\0" (NUL) was no longer allowed in environment variables, and fixed things up as change #27359. Jarkko also supplied another patch for the same thing, which Rafael also applied. http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/2006-03/msg00025.html http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/2006-03/msg00052.html Getting back to last week's thread on unwanted auto-vivification with "foreach", David Nicol showed a snippet of code that offers a way of working around the problem, and wondered whether the documentation should record it somewhere. Graham Barr noted that using "reverse" also suppresses the auto-vivification behaviour. And that if you didn't want a slice reversed, you needed to "reverse reverse". There's at least one way to do it http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/2006-03/msg00044.html Jarkko added a test to "Data::Dumper"'s test suite to ensure that the bug #38612 that was fixed in 5.8.7 never returns. http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/2006-03/msg00049.html H.Merijn added "Configure" support for the GCC compiler options "__builtin_expect" and "__builtin_choose_expr". http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/2006-03/msg00063.html Paul Marquess delivered a patch for "Compress::Zlib", following on from his recent work to add compression plugins. http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/2006-03/msg00064.html Joshua start to have a look at the new smart match operator "~~" and found a discrepancy between its behaviour and that of Pugs/Perl6. http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/2006-03/msg00081.html Abe Timmerman patched Porting/checkcfgvar.pl to pick up configure.com and plunged unwittingly into the wonderful and frightening world of VMS symbols. John E. Malmberg and Craig A. Berry were sent in to rescue him. http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/2006-03/msg00090.html Abe then thought it would be a good idea to see what happens when one builds a threaded perl on VMS. In the process he uncovered a couple of problems that John and Craig sorted out. http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/2006-03/msg00139.html Dave Rolsky wanted to know if nested closures still leak memory. Dave Mitchell thought that no closure leakage bugs remained in "blead", but pointed out that not all of the new code had made it back into "maint". Until proven otherwise http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/2006-03/msg00103.html Randy W. Sims want to install an older perl on his Ubuntu linux distribution, but the install began to create an infinitely deep directory tree. On and on and on http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/2006-03/msg00148.html Linda W gave a report on the effects of configuration options on the resulting perl binary. http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/2006-03/msg00161.html Perl can no longer be compiled with a K&R compiler. http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/2006-03/msg00160.html David Nicol posted his thought on what he would like to see in the way of plug-in optimisers. A optimistic optimiser could optimise a section of code, and then, if some assumption failed to hold true, it could de-optimise the code back to the initial state. I think some proof-of-concept code will be required. http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/2006-03/msg00174.html About this summary This summary was written by David Landgren. Information concerning bugs referenced in this summary (as #nnnnn) may be viewed at http://rt.perl.org/rt3/Ticket/Display.html?id=nnnnn Information concerning patches to "maint" or "blead" referenced in this summary (as #nnnnn) may be viewed at http://public.activestate.com/cgi-bin/perlbrowse?patch=nnnnn 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."
