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

[Rik]

Update of bug #57284 (project octave):

                  Status:                    None => Invalid                
             Open/Closed:                    Open => Closed                 

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Follow-up Comment #2:

This is invalid syntax.  The programmer needs to check the value of the
variable 'nlhs', which is the number of left-hand side variables, and only
write to variables which exist.  Prior to entering the mex function the Octave
interpreter has taken care of allocating an array of pointers to mxArray which
is sized according to the value of 'nlhs' and is given as the second argument
of the function:


mxArray *plhs[]


It is no surprise that trying to assign to unallocated memory results in
segfaults.

This is one of the reasons that Appendix A which discusses the mex and oct
file interfaces recommends staying within the Octave language if at all
possible.  Once you leave the interpreter you are programming for real and
stack overflows, segmentation faults, infinite loops, out-of-memory errors,
etc., etc. are all possible.


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