[Octave-bug-tracker] [bug #56232] Octave crash when inverting an empty sparse matrix.

[Rik]

Follow-up Comment #30, bug #56232 (project octave):

I'm attaching a file mex_sparse.c that we need someone to compile and run in
Matlab to verify what it does.  On looking through the documentation, it seems
that nzmax must always be a minimum of 1.  I.e., they always allocate space
for at least one element.

Within Matlab, I tried


S = sparse (zeros (2));
nzmax (S)
=> 1


so this minimum is preserved in the interpreter as well, not just the mex
interface.

After compiling and running the mex_sparse.c in Octave I get


octave:4> mex_sparse
Reported nzmax size when created with 0 elements: 0
mxGetIr returns valid pointer when nzmax == 0
mxGetPr returns valid pointer when nzmax == 0
Reported nzmax size when created with 1 elements: 1
mxGetIr returns valid pointer when nzmax == 1
mxGetPr returns valid pointer when nzmax == 1


So Octave allows the creation of fully empty (nzmax = 0, nnz = 0) sparse
matrices.  The pointer returned from mxGetIr and mxGetPr is not NULL even in
this instance.



(file #46880)
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Additional Item Attachment:

File name: mex_sparse.c                   Size:1 KB
    <https://savannah.gnu.org/file/mex_sparse.c?file_id=46880>



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