[Rock-dev] LD_LIBRARY_PATH and Qt::UiLoader Segfault

[Alexander Duda]

I found the reason. 

usr/lib/libqtruby4shared.so.2.0.0 is installed into /usr/lib by default
but I also had a version in /usr/local/lib (I do not know why) which was
picked up after LD_LIBRARY_PATH was extended. After deleting the one
from /usr/local/lib the problem disappeared.

Hmmm - not so nice 
 
Alex


On Wed, 2011-08-31 at 16:09 +0200, Alexander Duda wrote:
> In my case it is crashing:
> 
> gbd:
> Program received signal SIGSEGV, Segmentation fault.
> 0xb674f840 in findMethod(unsigned long, unsigned long, unsigned long) ()
> from /usr/local/lib/libqtruby4shared.so.2
> (gdb) bt
> #0  0xb674f840 in findMethod(unsigned long, unsigned long, unsigned
> long) () from /usr/local/lib/libqtruby4shared.so.2
> #1  0xb7f2a992 in ?? () from /usr/lib/libruby1.8.so.1.8
> #2  0xb7f36151 in ?? () from /usr/lib/libruby1.8.so.1.8
> #3  0xb7f362ea in ?? () from /usr/lib/libruby1.8.so.1.8
> #4  0xb7f3345c in ?? () from /usr/lib/libruby1.8.so.1.8
> #5  0xb7f30c6e in ?? () from /usr/lib/libruby1.8.so.1.8
> #6  0xb7f34b1b in ?? () from /usr/lib/libruby1.8.so.1.8
> #7  0xb7f40127 in rb_yield () from /usr/lib/libruby1.8.so.1.8
> ...
> 
> valgrind (see file attached):
> ==9034== Invalid read of size 4
> ==9034==    at 0x6A47840: findMethod(unsigned long, unsigned long,
> unsigned long) (in /usr/local/lib/libqtruby4shared.so.2.0.0)
> ==9034==    by 0x4056991: ??? (in /usr/lib/libruby1.8.so.1.8.7)
> ==9034==    by 0x4062150: ??? (in /usr/lib/libruby1.8.so.1.8.7)
> ==9034==    by 0x40622E9: ??? (in /usr/lib/libruby1.8.so.1.8.7)
> ==9034==    by 0x405F45B: ??? (in /usr/lib/libruby1.8.so.1.8.7)
> ==9034==    by 0x405CC6D: ??? (in /usr/lib/libruby1.8.so.1.8.7)
> ==9034==    by 0x4060B1A: ??? (in /usr/lib/libruby1.8.so.1.8.7)
> ==9034==    by 0x406C126: rb_yield (in /usr/lib/libruby1.8.so.1.8.7)
> ==9034==    by 0x4040548: ??? (in /usr/lib/libruby1.8.so.1.8.7)
> ==9034==    by 0x40569AC: ??? (in /usr/lib/libruby1.8.so.1.8.7)
> ==9034==    by 0x4062150: ??? (in /usr/lib/libruby1.8.so.1.8.7)
> ==9034==    by 0x40622E9: ??? (in /usr/lib/libruby1.8.so.1.8.7)
> ==9034==  Address 0x8 is not stack'd, malloc'd or (recently) free'd
> ==9034== 
> /usr/lib/ruby/1.8/Qt/qtruby4.rb:2708: [BUG] Segmentation fault
> ruby 1.8.7 (2010-01-10 patchlevel 249) [i486-linux]
> 
> 
> On Wed, 2011-08-31 at 15:01 +0200, Sylvain Joyeux wrote:
> > On 08/31/2011 02:14 PM, Alexander Duda wrote:
> > > On Wed, 2011-08-31 at 11:59 +0200, Sylvain Joyeux wrote:
> > >> On 08/31/2011 11:18 AM, Alexander Duda wrote:
> > >>> Someone extended the environment variable LD_LIBRARY_PATH (env.sh) with
> > >>> "/lib". The Qt::UiLoader cannot handle this and crashes.
> > >>>
> > >>> Question:
> > >>> -Why was /lib added?
> > >> It is a byproduct of the workaround in autobuild for debian rolling out
> > >> multiarch.
> > >>
> > >> In a nutshell, on Debian, pkg-config and libraries can now get installed
> > >> in /lib/<ARCH>  and /usr/lib/<ARCH>
> > >>
> > >> To avoid issues with that, I started adding these to the
> > >> PKG_CONFIG_PATH. I also added them to LD_LIBRARY_PATH as at the time I
> > >> saw no drawbacks.
> > >>> -Has someone else the same problem?
> > >> How can I reproduce ? I tried loading the UILoader and starting the Qt
> > >> designer, and had no problems
> > > in my case it occurs by typing the following into the shell.
> > > . env.sh
> > > irb
> > > require 'Qt4'
> > > require 'qtuiloader'
> > > Qt::UiLoader.new
> > Just to be sure: I had to do
> > 
> >    require 'Qt4'
> >    require 'qtuitools'
> >    app = Qt::Application.new(ARGV)
> >    Qt::UiLoader.new
> > 
> > And it worked fine
> > 
> > Have you tried starting irb / ruby with a gdb to check where it breaks ? 
> > (or getting valgrind ?)
> 
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-- 
Dipl.-Ing. Alexander Duda 
Unterwasserrobotik

DFKI Bremen
Robotics Innovation Center
Robert-Hooke-Straße 5
28359 Bremen, Germany

Phone: +49 (0)421 178-456620
Fax:   +49 (0)421 178-454150
E-Mail: alexander.duda at dfki.de

Weitere Informationen: http://www.dfki.de/robotik
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