I've had consistent crashing when trying to use the bfsqrt method with AB09ND. I switched on debug mode, -fcheck=all and such. I was able to track it down after also poking around using valgrind. For future reference, it is nice to run test suites that fail with memory checking and gdb to poke around inside the stack traces. This is much better than just what -fcheck=all does.

PYTHONMALLOC=malloc valgrind --vgdb-error=1 python3 -m pytest <args>

see https://developers.redhat.com/articles/2021/11/01/debug-memory-errors-valgrind-and-gdb#discover_uninitialized_values for more details.

Anyway, for the bug fix. In the wrapper for AB09ND,

    integer intent(hide,cache),dimension(MAX(m,p)) :: iwork

should become

    integer intent(hide,cache),dimension(MAX(1,2*n)),depend(n) :: iwork

which makes it consistent with the requirements in the slicot source file, and also appears to fix the issue.