A segmentation fault can be produced in SageMath (valid in Sage 10.7.beta6) via the following operation:

sage: matrix.zero(GF(4),2,0).with_permuted_rows(Permutation([2,1]))

This calls mzed_row_swap -> mzd_row_swap -> _mzd_row_swap where the first line is this:

if ((rowa == rowb) || (startblock >= M->width)) { return; }

startblock and M->width are both expected to be 0, in which case the function should exit early.

However, instead this check looks like it's failing, and a segmentation fault is produced instead. It is likely M->width is not being correctly initialised to 0 for this matrix.

The problem also exists for _mzed_col_swap:

sage: matrix.zero(GF(4),0,2).with_permuted_columns(Permutation([2,1]))

Related PR (SageMath fix for the above issue): sagemath/sage#40291