Important update: the problem is nothing to do with Apache or mod_perl. The easiest demonstration:
> perl -le 'use PerlIO::via::QuotedPrint; binmode(\*STDERR, ":via(PerlIO::via::QuotedPrint):utf8"); open (ERROR, ">&STDERR");'
zsh: segmentation fault perl -le
In fact binmode
is performed by my code and open (ERROR, ">&STDERR");
by Parse::RecDescent.
Original question:
I have a problem with Spreadsheet::WriteExcel under mod_perl 2.0.5
Apache dies with segmentation fault, and I found out that it occurs on require Parse::RecDescent
statement within Spreadsheet::WriteExcel
package.
strace shows that last things that happens is dup'ing STDERR:
[pid 31253] dup(2) = 8
[pid 31253] ioctl(8, SNDCTL_TMR_TIMEBASE or TCGETS, 0x7fffcf66a328) = -1 ENOTTY (Inappropriate ioctl for device)
[pid 31253] lseek(8, 0, SEEK_CUR) = 0
[pid 31253] --- SIGSEGV (Segmentation fault) @ 0 (0) ---
I read through the code of Parse::RecDescent
and noticed statements like open (ERROR, ">&STDERR");
Well, after some additional experiments I have this minimalistic Plack app to reproduce the segfault:
use strict;
use warnings;
# DANGEROUS
use PerlIO::via::QuotedPrint;
binmode(\*STDERR, ":via(PerlIO::via::QuotedPrint):utf8");
my $app = sub {
my $env = shift;
open (ERROR, ">&STDERR"); # segmenatation fault
return [
'200',
[ 'Content-Type' => 'text/plain' ],
[ "hello world" ],
];
};
$app;
(In fact I use binmode layer other than PerlIO::via::QuotedPrint
, but effect is the same)
If I don't perform binmode(\*STDERR, ":via(PerlIO...
, apache doesn't segfault.
If I don't duplicate STDERR
, apache doesn't segfault.
If I do the both, it segfaults.
As a workaround I can avoid using binmode
on STDERR, but it's not good.
Any suggestions on where and how should be fixed this?
Thanks.
My environment:
perl -v |grep version
This is perl 5, version 14, subversion 2 (v5.14.2) built for x86_64-linux-gnu-thread-multi
uname -a
Linux thinkpad 3.2.0-32-generic #51-Ubuntu SMP Wed Sep 26 21:33:09 UTC 2012 x86_64 x86_64 x86_64 GNU/Linux
lsb_release -c
Codename: precise
dpkg -l |grep mod-perl
ii libapache2-mod-perl2 2.0.5-5ubuntu1 Integration of perl with the Apache2 web server
Upd: the same code works well under outdated Ubuntu 8.04 + perl 5.8.8 + mod_perl2 2.0.3
Upd2: FreeBSD 9.1 + perl 5.14 + mod_perl 2.0.8 -- segfault repeats
uname -a
FreeBSD liruoko.ru 9.1-RELEASE-p5 FreeBSD 9.1-RELEASE-p5 #7 r253740: Sun Jul 28 16:53:08 MSK 2013 roman@thor.cmc.msu.ru:/usr/obj/usr/src/sys/MINI amd64
pkg info |grep apache
apache22-itk-mpm-2.2.25 Version 2.2.x of Apache web server with itk MPM.
pkg info |grep mod_perl
ap22-mod_perl2-2.0.8,3 Embeds a Perl interpreter in the Apache2 server
perl -v |grep version
This is perl 5, version 14, subversion 4 (v5.14.4) built for amd64-freebsd
If it works without binmode
set, then perhaps you have a solution (if not a real answer to why this is happening). c.f. this extract from perldoc -f binmode
:
On some systems (in general, DOS- and Windows-based systems) binmode() is
necessary when you're not working with a text file. For the sake of portability
it is a good idea always to use it when appropriate, and never to use it when it
isn't appropriate. Also, people can set their I/O to be by default UTF8-encoded
Unicode, not bytes.
In other words: regardless of platform, use binmode() on binary data, like
images, for example. ...
In the inimitable style of perldoc
I think that might be suggesting you could set binmode
for certain filehandles/sockets and not for others adjusting until the "bug" (if it is one) does not appear.
EDIT:
Thanks to your simple and reproducible error / test case I think this will get fixed. I built a debug version of perl
to try tracing the error and it is in liberperl.so
- somewhere in PerlIOBase_dup()
. I also mentioned this on IRC to people who would know, and they concluded this is a real (i.e reportable) perl
bug.
Here's how I ran gdb
:
(gdb) run -Dx -le 'use PerlIO::via::QuotedPrint; binmode(\*STDERR,
":via(PerlIO::via::QuotedPrint):utf8"); open (ERROR, ">&STDERR");'
and this was how things ended up:
Program received signal SIGSEGV, Segmentation fault.
PerlIOBase_dup (f=0x0, o=0x801551060, param=0x0, flags=2) at perlio.c:2307
2307 PerlIOBase(f)->flags |= PERLIO_F_UTF8;
Cheers, you made perl
better!