Exemplary steps to debug segfaulting .mex* files in MATLAB (on a Linux platform)

DebugMexFilesOnLinux

1) Compile your code (using mex) with -g flag
2) Call gdb via MATLAB's 'matlab -Dgdb' functionality
3) Set a breakpoint for instance by 'break testfile.cpp:9'
3) Run MATLAB without the JVM by 'run -nojvm'
4) Now, run the segfaulting mex function 
5) Get a backtrace via 'bt' and use your debugging magic

Example:

$ cd '/mycode/
$ mex -g testfun.cpp
$ matlab -Dgdb
>> break testfun.cpp:20
>> run -nojvm
>> testfun 
...
(Now the segfault happens)
>> bt