CODEWITHSUNDEEP
matlabsegmentation-faultgdbmexdisassembly
kameranis
kameranis

Reputation: 284

Correlate stack trace with source code in MATLAB .mexa64 file

I have custom C bindings called from Matlab and sometimes I get a segmentation fault. How can I identify in my source code what the corresponding statement is producing the SEGFAULT?

My C function is called Pairing in the source file Pairing.c

Stack Trace (from fault):
[  0] 0x00007fff6bc76d00 Pairing.mexa64+00015616
[  1] 0x00007fff6bc74330 Pairing.mexa64+00004912 mexFunction+00001862
[  2] 0x00007fffe2b4f213 MATLAB/R2020a/bin/glnxa64/libmex.so+00582163

The result of nm -a Pairing.mexa64 | grep ' N ' is

0000000000000000 N .debug_abbrev
0000000000000000 N .debug_aranges
0000000000000000 N .debug_info
0000000000000000 N .debug_line
0000000000000000 N .debug_str

Upvotes: 1

Views: 349

Answers (2)

FangQ
FangQ

Reputation: 1544

here is my trick (works every single time), run this in a terminal window

matlab -nojvm -nosplash -r 'my_script'  -D"valgrind --error-limit=no --tool=memcheck -v --log-file=valgrind.log"

preferably run this under Linux or Mac, but you can also do this in Windows using cygwin64/msys2. Need to install valgrind before use - once it dumps the log in valgrind.log, open it using a text editor, and you can see all memory errors captured by valgrind.

for CUDA codes, you can also replace the valgrind command and parameters by cuda-memcheck, does something similar, but for the GPU.

make your test script my_script.m very simple, for example, load a .mat file, and then call your mex function immediately to avoid lengthy overhead.

Upvotes: 3

kameranis
kameranis

Reputation: 284

The way I solved it was following these steps

1) Use objdump -d Pairing.mexa64 > Pairing_obj.

2) Translate 00015616 to hex=0x3d00.

3) Find the relevant statement and recognize the produced assembly.

4) Realize this is the first time a certain variable is dereferenced.

I am still looking for some way that this could be done easier.

Upvotes: 0

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