Segmentation fault

rks has asked for the wisdom of the Perl Monks concerning the following question:

Replies are listed 'Best First'.
Re: Segmentation fault by tobyink (Canon) on Jul 03, 2012 at 14:26 UTC
Segfaults are often caused by your script causing something internal within Perl to go into an infinite loop. Perl's generally smart enough to cope with your script looping infinitely, but can sometimes be tricked into an infinite loop and segfault in its internals. An example script that causes a segfault in Perl 5.10 to 5.16 (and perhaps 5.17 as well?) `use 5.010; use strict; my $a = ['a', 'A']; my $b = ['b', $a, 'B']; push @$a, $b; say "hurrah!" if 'x' ~~ $a;` [download] The smart match operator is tricked into switching between the two arrayrefs eternally. Each time it follows a reference between the arrays, the stack size grows a little bigger, until bang! Segfault! Why your script in particular causes a segfault, we cannot determine without seeing it. `perl -E'sub Monkey::do{say$_,for@_,do{($monkey=[caller(0)]->[3])=~s{::}{ }and$monkey}}"Monkey say"->Monkey::do'`	[reply] [d/l]
Re: Segmentation fault by daxim (Curate) on Jul 03, 2012 at 14:20 UTC
Start the `cpan` shell and run the command `recompile`.	[reply]
Re^2: Segmentation fault by locked_user sundialsvc4 (Abbot) on Jul 03, 2012 at 15:10 UTC
Exactly. Remember that every CPAN module includes as part of its implementation a fair amount of C/C++ (so called “XS”) code. When you change versions of the Perl executable, you will ex minimis need to recompile the versions of what you have. You probably should `upgrade` them, too. There’s a lot of “magic” in the install-scripts, and some of that might be Perl-version aware. When you have changed the layer of software that’s at the bottom of it all (“Perl itself...”), you need to re-do these things so that everyone’s once again singing from the same songbook.
Re^3: Segmentation fault by dasgar (Priest) on Jul 03, 2012 at 15:48 UTC
Every CPAN module has "C/C++ (so called "XS") code"? Perhaps I don't know what I'm talking about, but aren't there "pure Perl" modules in CPAN that don't have any C/C++/XS code in them? (i.e. only Perl code) Actually, after re-reading your wording, maybe I misunderstood you. Are you saying "every module in CPAN" has C/C++ code or are you just talking about the CPAN module itself that has C/C++ code?	[reply]
Re^4: Segmentation fault by locked_user sundialsvc4 (Abbot) on Jul 03, 2012 at 20:19 UTC
Re^2: Segmentation fault by ig (Vicar) on Jul 03, 2012 at 20:01 UTC
If Perl was installed from platform packages and upgraded this way, it might be best to avoid running `cpan` against it. Mixing platform packages with installations from cpan can lead to difficulties.	[reply] [d/l]
Re: Segmentation fault by ig (Vicar) on Jul 03, 2012 at 20:05 UTC
Do you get a segmentation fault with all your scripts? Or is your problem with one particular script? If most work but one fails, it would make sense to investigate that one script in more detail. If most or all scripts are failing, then your installation of perl needs attention. If you provide a bit more information, there are monks who can help you in either case.	[reply]
Re^2: Segmentation fault by rks (Initiate) on Jul 04, 2012 at 14:00 UTC
Hi All, Thanks for all your replies. It is working after recompiling cpan as per daxim reply. Once again, thanks for your responses. -rks-	[reply]