[Octave-bug-tracker] [bug #57284] Crash in MEX file when outputs are not used

[Rik]

Follow-up Comment #13, bug #57284 (project octave):

For consistency, if we are not expecting programmers to check the number of
outputs before using them then we should do something similar for inputs. 
Here is a small file "mexin.c" that sums its inputs.


#include "mex.h"

void mexFunction(int nlhs, mxArray *plhs[], int nrhs, const mxArray *prhs[])
{
  int count = mxGetScalar (prhs[0]);

  double sum = 0.0;
  
  for (int i = 1; i <= count; i++)
    sum += mxGetScalar (prhs[i]);

  plhs[0] = mxCreateDoubleScalar (sum);
}


It is a pretty common problem that programmers can't imagine that their
function would be called in the wrong way, and don't put any input validation
to verify their assumptions.  For example, a function named "add_two_numbers"
is likely meant to be called as "add_two_numbers (a, b)".  But you know that
somewhere, at sometime, someone is going to get it wrong. 

Unlike the output case, I get a segfault on the input whenever I exceed nrhs
by even 1. 


mexin (2, 1)
fatal: caught signal Segmentation fault -- stopping myself...
Segmentation fault (core dumped)




(file #47918)
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Additional Item Attachment:

File name: mexin.c                        Size:0 KB
    <https://savannah.gnu.org/file/mexin.c?file_id=47918>



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