How to solve segmentation violation error when I call a C-MEX function which is compiled correctly?

Hi;

I have compiled a C-mex file in matlab successfully. But, when I try to call it in a matlab program, "Segmentation violation" error appears and Matlab is forced to close. The error which I get is:

------------------------------------------------------------------------
       Segmentation violation detected at Wed Apr 27 16:51:04 2015
------------------------------------------------------------------------

Configuration:
  Crash Decoding      : Disabled
  Crash Mode          : continue (default)
  Current Graphics Driver: Unknown hardware 
  Current Visual      : 0x23 (class 4, depth 24)
  Default Encoding    : UTF-8
  GNU C Library       : 2.19 stable
  Host Name           : iampc25
  MATLAB Architecture : glnxa64
  MATLAB Root         : /opt/MATLAB/R2015a
  MATLAB Version      : 8.5.0.197613 (R2015a)
  OpenGL              : hardware
  Operating System    : Linux 3.19.0-32-generic #37~14.04.1-Ubuntu SMP x86_64
  Processor ID        : x86 Family 6 Model 60 Stepping 3, GenuineIntel
  Virtual Machine     : Java 1.7.0_60-b19 with Oracle Corporation Java HotSpot(TM) 64-Bit Server VM mixed mode
  Window System       : The X.Org Foundation (11701000), display :0

Fault Count: 1

Abnormal termination:
Segmentation violation

Register State (from fault):

RAX = 00007f94bdadd7f0  RBX = 0000000000000001
RCX = 00007f95d6d0c320  RDX = 00007f95e3ede870
RSP = 00007f95e3ede520  RBP = 00007f95e3ede8b0
RSI = 00007f95d6d0c358  RDI = 0000000000000008

   R8 = 000bf5f8000000c0   R9 = 0000000000000008
  R10 = 0003fca800000040  R11 = 0003fca800000040
  R12 = 000bf5f8000000c0  R13 = 00007f95e3ede870
  R14 = 00007f95d6d0c320  R15 = 00007f95e3ede870

RIP = 00007f94bdaddeda  EFL = 0000000000010202

   CS = 0033   FS = 0000   GS = 0000

Stack Trace (from fault):

[  0] 0x00007f94bdaddeda              /opt/MATLAB/R2015a/bin/glnxa64/mkl.so+15728346
[  1] 0x0000000000000000                                   <unknown-module>+00000000

This error was detected while a MEX-file was running. If the MEX-file
is not an official MathWorks function, please examine its source code
for errors. Please consult the External Interfaces Guide for information
on debugging MEX-files.

any help is appreciated !!

[Walter Roberson]

Compiled without error does not mean that the code is correct.

We will need to see the code to have a hope of locating the problem.

[MA]

Unfortunately the code is too long, I am afraid if I can post it here. you are right, when it compiles it does not mean the code is right, but when I try to run on unix prompt everything is alright and works, but in MATLAB I get the error.

[Walter Roberson]

MATLAB imposes its own dynamic library path. Compare the DYLD_LIBRARY_PATH environment variable outside of MATLAB with the one inside MATLAB. In particular for your situation pay attention to where mkl.so is being found. You may wish to use ldd to see where it need to load it from.

[MA]

Could you please provide some more guide how to do that?

Answer 1

[Alessandro Masullo]

I suggest you to run a debugger on your C file. I've never done it on GNU/Linux, but it should be possible in the same way as on Windows.

Simply open your debugger, attach it to the process of Matlab, compile your mex file with "-g", set a debug point in your mex routine, run it from matlab and execute your C file line by line. When Matlab crashes, you can see exactly where your C file is generating the error.

Hope it helps.