Hi,

try compiling ImageMagick without OpenMP support and see if this helps

(Your system doesn't like my password anymore)

After compiling ImageMagick without OpenMP support segfault doesn't occur. But it still sends a messages about detected memory leaks.

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I tried to do the following:
CFLAGS="-ggdb3" CXXFLAGS="${CFLAGS}" LDFLAGS="-Wl,-O1 -Wl,--as-needed" FEATURES="nostrip" USE="debug -openmp" emerge -1 media-gfx/imagemagick

After compilation I tried gdb again:
# gdb /usr/bin/php
GNU gdb (Gentoo 7.2 p1) 7.2
Copyright (C) 2010 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.  Type "show copying"
and "show warranty" for details.
This GDB was configured as "x86_64-pc-linux-gnu".
For bug reporting instructions, please see:
<http://bugs.gentoo.org/>...
Reading symbols from /usr/bin/php...done.
(gdb) set args /var/www/myhost/htdocs/imr/update-test.php
(gdb) r
Starting program: /usr/bin/php /var/www/myhost/htdocs/imr/update-test.php
warning: Unable to find libthread_db matching inferior's thread library, thread debugging will not be available.
warning: Unable to find libthread_db matching inferior's thread library, thread debugging will not be available.
warning: Unable to find libthread_db matching inferior's thread library, thread debugging will not be available.
warning: Unable to find libthread_db matching inferior's thread library, thread debugging will not be available.
warning: Unable to find libthread_db matching inferior's thread library, thread debugging will not be available.
warning: Unable to find libthread_db matching inferior's thread library, thread debugging will not be available.
warning: Unable to find libthread_db matching inferior's thread library, thread debugging will not be available.
warning: Unable to find libthread_db matching inferior's thread library, thread debugging will not be available.
warning: Unable to find libthread_db matching inferior's thread library, thread debugging will not be available.
warning: Unable to find libthread_db matching inferior's thread library, thread debugging will not be available.
warning: Unable to find libthread_db matching inferior's thread library, thread debugging will not be available.
warning: Unable to find libthread_db matching inferior's thread library, thread debugging will not be available.
warning: Unable to find libthread_db matching inferior's thread library, thread debugging will not be available.
warning: Unable to find libthread_db matching inferior's thread library, thread debugging will not be available.
warning: Unable to find libthread_db matching inferior's thread library, thread debugging will not be available.
warning: Unable to find libthread_db matching inferior's thread library, thread debugging will not be available.
warning: Unable to find libthread_db matching inferior's thread library, thread debugging will not be available.
warning: Unable to find libthread_db matching inferior's thread library, thread debugging will not be available.
warning: Unable to find libthread_db matching inferior's thread library, thread debugging will not be available.
warning: Unable to find libthread_db matching inferior's thread library, thread debugging will not be available.
warning: Unable to find libthread_db matching inferior's thread library, thread debugging will not be available.
warning: Unable to find libthread_db matching inferior's thread library, thread debugging will not be available.
warning: Unable to find libthread_db matching inferior's thread library, thread debugging will not be available.
warning: Unable to find libthread_db matching inferior's thread library, thread debugging will not be available.
warning: Unable to find libthread_db matching inferior's thread library, thread debugging will not be available.
warning: Unable to find libthread_db matching inferior's thread library, thread debugging will not be available.
warning: Unable to find libthread_db matching inferior's thread library, thread debugging will not be available.
[New LWP 26223]
[LWP 26223 exited]
warning: Unable to find libthread_db matching inferior's thread library, thread debugging will not be available.
warning: Unable to find libthread_db matching inferior's thread library, thread debugging will not be available.
warning: Unable to find libthread_db matching inferior's thread library, thread debugging will not be available.
warning: Unable to find libthread_db matching inferior's thread library, thread debugging will not be available.
[Fri May  6 19:22:19 2011]  Script:  '/var/www/myhost/htdocs/imr/update-test.php'
/var/tmp/portage/dev-lang/php-5.3.6/work/sapis-build/cli/Zend/zend_vm_execute.h(475) :  Freeing 0x016F7F18 (32 bytes), script=/var/www/myhost/htdocs/imr/update-test.php
Last leak repeated 41 times
[Fri May  6 19:22:19 2011]  Script:  '/var/www/myhost/htdocs/imr/update-test.php'
/var/tmp/portage/dev-lang/php-5.3.6/work/sapis-build/cli/Zend/zend_vm_execute.h(300) :  Freeing 0x016F97E8 (32 bytes), script=/var/www/myhost/htdocs/imr/update-test.php
Last leak repeated 41 times
=== Total 84 memory leaks detected ===

Program exited normally.
(gdb) bt full
No stack.
(gdb) q

Then I tried to recompile imagemagick with openmp again:
CFLAGS="-ggdb3" CXXFLAGS="${CFLAGS}" LDFLAGS="-Wl,-O1 -Wl,--as-needed" FEATURES="nostrip" USE="debug" emerge -1 media-gfx/imagemagick

These are the packages that would be merged, in reverse order:

Calculating dependencies... done!
[ebuild   R   ] media-gfx/imagemagick-6.6.8.5  USE="X bzip2 corefonts cxx djvu jpeg jpeg2k lcms lzma openmp* perl png svg tiff truetype webp wmf xml zlib -autotrace -fftw -fontconfig -fpx -graphviz -gs -hdri -jbig -lqr -openexr -q32 -q8 -raw -static-libs" VIDEO_CARDS="nvidia" 0 kB 

Total: 1 package (1 reinstall), Size of downloads: 0 kB

It generates segfaults and doesn't give more useful debugging info unfortunatelly despite the fact that I tried to compile php, imagick and imagemagick with debug symbols:

# gdb /usr/bin/php
GNU gdb (Gentoo 7.2 p1) 7.2
Copyright (C) 2010 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.  Type "show copying"
and "show warranty" for details.
This GDB was configured as "x86_64-pc-linux-gnu".
For bug reporting instructions, please see:
<http://bugs.gentoo.org/>...
Reading symbols from /usr/bin/php...done.
(gdb) set args /var/www/myhost/htdocs/imr/update-test.php
(gdb) r
Starting program: /usr/bin/php /var/www/myhost/htdocs/imr/update-test.php
warning: Unable to find libthread_db matching inferior's thread library, thread debugging will not be available.
warning: Unable to find libthread_db matching inferior's thread library, thread debugging will not be available.
warning: Unable to find libthread_db matching inferior's thread library, thread debugging will not be available.
warning: Unable to find libthread_db matching inferior's thread library, thread debugging will not be available.
warning: Unable to find libthread_db matching inferior's thread library, thread debugging will not be available.
warning: Unable to find libthread_db matching inferior's thread library, thread debugging will not be available.
warning: Unable to find libthread_db matching inferior's thread library, thread debugging will not be available.
warning: Unable to find libthread_db matching inferior's thread library, thread debugging will not be available.
warning: Unable to find libthread_db matching inferior's thread library, thread debugging will not be available.
warning: Unable to find libthread_db matching inferior's thread library, thread debugging will not be available.
warning: Unable to find libthread_db matching inferior's thread library, thread debugging will not be available.
warning: Unable to find libthread_db matching inferior's thread library, thread debugging will not be available.
warning: Unable to find libthread_db matching inferior's thread library, thread debugging will not be available.
warning: Unable to find libthread_db matching inferior's thread library, thread debugging will not be available.
warning: Unable to find libthread_db matching inferior's thread library, thread debugging will not be available.
warning: Unable to find libthread_db matching inferior's thread library, thread debugging will not be available.
warning: Unable to find libthread_db matching inferior's thread library, thread debugging will not be available.
warning: Unable to find libthread_db matching inferior's thread library, thread debugging will not be available.
warning: Unable to find libthread_db matching inferior's thread library, thread debugging will not be available.
warning: Unable to find libthread_db matching inferior's thread library, thread debugging will not be available.
warning: Unable to find libthread_db matching inferior's thread library, thread debugging will not be available.
warning: Unable to find libthread_db matching inferior's thread library, thread debugging will not be available.
warning: Unable to find libthread_db matching inferior's thread library, thread debugging will not be available.
warning: Unable to find libthread_db matching inferior's thread library, thread debugging will not be available.
warning: Unable to find libthread_db matching inferior's thread library, thread debugging will not be available.
warning: Unable to find libthread_db matching inferior's thread library, thread debugging will not be available.
warning: Unable to find libthread_db matching inferior's thread library, thread debugging will not be available.
warning: Unable to find libthread_db matching inferior's thread library, thread debugging will not be available.
warning: Unable to find libthread_db matching inferior's thread library, thread debugging will not be available.
[New LWP 14755]
[LWP 14755 exited]
warning: Unable to find libthread_db matching inferior's thread library, thread debugging will not be available.
warning: Unable to find libthread_db matching inferior's thread library, thread debugging will not be available.
warning: Unable to find libthread_db matching inferior's thread library, thread debugging will not be available.
warning: Unable to find libthread_db matching inferior's thread library, thread debugging will not be available.
[Fri May  6 19:28:15 2011]  Script:  '/var/www/myhost/htdocs/imr/update-test.php'
/var/tmp/portage/dev-lang/php-5.3.6/work/sapis-build/cli/Zend/zend_vm_execute.h(475) :  Freeing 0x016F8DA8 (32 bytes), script=/var/www/myhost/htdocs/imr/update-test.php
Last leak repeated 41 times
[Fri May  6 19:28:15 2011]  Script:  '/var/www/myhost/htdocs/imr/update-test.php'
/var/tmp/portage/dev-lang/php-5.3.6/work/sapis-build/cli/Zend/zend_vm_execute.h(300) :  Freeing 0x016FA678 (32 bytes), script=/var/www/myhost/htdocs/imr/update-test.php
Last leak repeated 41 times
=== Total 84 memory leaks detected ===
[New LWP 14757]
[New LWP 14756]

Program received signal SIGSEGV, Segmentation fault.
[Switching to LWP 14756]
0x00007ffff5835fd8 in ?? ()
(gdb) bt full
#0  0x00007ffff5835fd8 in ?? ()
No symbol table info available.
#1  0x00007ffff5834906 in ?? ()
No symbol table info available.
#2  0x0000000000000000 in ?? ()
No symbol table info available.
(gdb) q
A debugging session is active.

        Inferior 1 [process 14752] will be killed.

Quit anyway? (y or n) y

I generated also straces for you without (strace-openmp.log) and with (strace+openmp.log) OpenMP. You can download it from there:
http://www.filefactory.com/file/cb2e9a0/n/strace_tar_lzma

Can you run the script with:

USE_ZEND_ALLOC=0 valgrind php script.php

# USE_ZEND_ALLOC=0 valgrind /usr/bin/php /var/www/myhost/htdocs/imr/update-test.php
==19633== Memcheck, a memory error detector
==19633== Copyright (C) 2002-2010, and GNU GPL'd, by Julian Seward et al.
==19633== Using Valgrind-3.6.1 and LibVEX; rerun with -h for copyright info
==19633== Command: /usr/bin/php /var/www/myhost/htdocs/imr/update-test.php
==19633== 

valgrind:  Fatal error at startup: a function redirection
valgrind:  which is mandatory for this platform-tool combination
valgrind:  cannot be set up.  Details of the redirection are:
valgrind:  
valgrind:  A must-be-redirected function
valgrind:  whose name matches the pattern:      strlen
valgrind:  in an object with soname matching:   ld-linux-x86-64.so.2
valgrind:  was not found whilst processing
valgrind:  symbols from the object with soname: ld-linux-x86-64.so.2
valgrind:  
valgrind:  Possible fixes: (1, short term): install glibc's debuginfo
valgrind:  package on this machine.  (2, longer term): ask the packagers
valgrind:  for your Linux distribution to please in future ship a non-
valgrind:  stripped ld.so (or whatever the dynamic linker .so is called)
valgrind:  that exports the above-named function using the standard
valgrind:  calling conventions for this platform.  The package you need
valgrind:  to install for fix (1) is called
valgrind:  
valgrind:    On Debian, Ubuntu:                 libc6-dbg
valgrind:    On SuSE, openSuSE, Fedora, RHEL:   glibc-debuginfo
valgrind:  
valgrind:  Cannot continue -- exiting now.  Sorry.

That's not very helpful output

I tried to recompile glibc in debug mode:
# CFLAGS="-ggdb3" CXXFLAGS="${CFLAGS}" LDFLAGS="-Wl,-O1 -Wl,--as-needed" FEATURES="nostrip" USE="debug" emerge -1 glibc

These are the packages that would be merged, in reverse order:

Calculating dependencies... done!
[ebuild   R   ] sys-libs/glibc-2.11.3  USE="debug* glibc-omitfp (multilib) nls -gd (-hardened) -profile (-selinux) -vanilla" 0 kB

Total: 1 package (1 reinstall), Size of downloads: 0 kB

>>> Verifying ebuild manifests
>>> Emerging (1 of 1) sys-libs/glibc-2.11.3
>>> Installing (1 of 1) sys-libs/glibc-2.11.3
>>> Jobs: 1 of 1 complete                           Load avg: 2.03, 4.28, 5.65
>>> Auto-cleaning packages...

And Then I tried valgrind again. There's a log of
# USE_ZEND_ALLOC=0 valgrind /usr/bin/php /var/www/myhost/htdocs/imr/update-test.php

http://www.filefactory.com/file/cb2f107/n/valgrind_log_tar_lzma

Try setting the thread limit:

$img->setResourceLimit(6, 1); // 6 means "thread limit" resource, 1 means limit 
threads to 1.

OK, I'll try to set ResourceLimit and see what will happen.

I've just tried to get threads' type ResourceLimit value:
$im->getResourceLimit(6);
It is set to 4 in my case.
Then I tried to set
$im->setResourceLimit(6, 1);
And script completed fine without any problems.
Then, I tried to set 1 additional thread with:
$im->setResourceLimit(6, 2);
And the script gave me segfault again.
I think it's your problem guys with threads. So you should fix it somehow.

BTW, I'm using the following versions of software and still getting segfaults:
dev-lang/php-5.3.10
dev-php/pecl-imagick-3.1.0_rc1
media-gfx/imagemagick-6.7.6.4

Hi, 

Unfortunately there is nothing to fix in the Imagick code to address the problem. The issue is caused by the OpenMP library that is present on your system.

There is no way to fix it as the Imagick code doesn't call it; instead Imagick calls the ImageMagick code, which in turns calls the OpenMP library.

For future reference, please could you say which version of libgomp you have on your system - or whichever package is providing the OpenMP implementation.