Seg fault associated with MEX file?

I'm getting a seg fault show up while running a matlab script that includes a call to a MEX file. The MEX file is called exactly once, and I've checked that the crash does not actually happen during the invocation of the MEX file by displaying text just before and after the MEX call. I'm working on trying to narrow down the location of the seg fault, but the script is long and only crashes after a couple of hours so this is tricky. Any other ideas? Here is the crash dump:

Abnormal termination: Segmentation violation

Register State (from fault): EAX = 00ba840f EBX = 01208728 ECX = a3a60fb0 EDX = 1342d000 ESP = 048d8e2c EBP = 048d8e68 ESI = 00bc426b EDI = 00000000

EIP = 00000000  EFL = 00010246

   CS = 00000073   DS = 0000007b   SS = 0000007b
   ES = 0000007b   FS = 00000000   GS = 00000033

Stack Trace (from fault): [ 0] 0x00941099 /usr/local/MATLAB/R2011a_Student/bin/glnx86/../../bin/glnx86/libmwfl.so+00450713 fl::sysdep::linux::unwind_stack(void const**, unsigned int, unsigned int, fl::diag::thread_context const&)+000036 [ 1] 0x008f224a /usr/local/MATLAB/R2011a_Student/bin/glnx86/../../bin/glnx86/libmwfl.so+00127562 fl::diag::stacktrace_base::capture(fl::diag::thread_context const&, unsigned int)+000180 [ 2] 0x008fc473 /usr/local/MATLAB/R2011a_Student/bin/glnx86/../../bin/glnx86/libmwfl.so+00169075 [ 3] 0x008fc845 /usr/local/MATLAB/R2011a_Student/bin/glnx86/../../bin/glnx86/libmwfl.so+00170053 fl::diag::terminate_log(char const*, fl::diag::thread_context const&, bool)+000115 [ 4] 0x002c0a0f /usr/local/MATLAB/R2011a_Student/bin/glnx86/../../bin/glnx86/libmwmcr.so+00375311 fl::diag::terminate_log(char const*, ucontext const*, bool)+000096 [ 5] 0x002bd8a6 /usr/local/MATLAB/R2011a_Student/bin/glnx86/../../bin/glnx86/libmwmcr.so+00362662 [ 6] 0x002bf56e /usr/local/MATLAB/R2011a_Student/bin/glnx86/../../bin/glnx86/libmwmcr.so+00370030 [ 7] 0x002c0154 /usr/local/MATLAB/R2011a_Student/bin/glnx86/../../bin/glnx86/libmwmcr.so+00373076 [ 8] 0x004c3410 __kernel_rt_sigreturn+000000

[sourish]

Try this to see if it works:

Step 1: load intel fortran compiler (ifort) onto your system

Step 2: In the matlab prompt, >>mex FC="ifort" filename.F (which means I am over riding the probable default gfortran with ifort)

Step 3: YOURLHS=filename(YOURRHS)

If this works, then it may imply that the problem is occurring in gfortran working on 64 bit architecture.

Hope this helps.

Answer 1

[Walter Roberson]

In such cases, your mex file has probably overwritten a pointer, or overwritten a data area that does not belong to it but which other code is depending upon to be correct. Or your mex file might be free()'ing something that it should not be.

[Kaustubha Govind]

+1

If you have the source code for the MEX-function, it may be useful to try debugging the file. See this page for information on debugging: http://www.mathworks.com/help/techdoc/matlab_external/f32489.html