Assertion failed: fr->magic == FLI_MAGIC

[swi]

It could be that some memory is getting corrupted.

Try running with swipl -d chk_secure which will enable some extra debugging/checks to see if you are corrupting a termref or something earlier in your code.

See this post:

Thank you! (foreign non-deterministic predicates)

Jan, Thank you so much for providing swipl -d chk_secure, without it, it would have been almost impossible to debug an error in my foreign code! Two warnings for all those who are doing non deterministic foreign predicates: don’t write code that references the term_t arguments outside of the switch statement which checks if the call is PL_FIRST_CALL, PL_REDO or PL_PRUNED. 2) don’t use the term_t references inside the PL_PRUNED case. Longer explanation: If an exception is thrown (after the…

This page has more info also:

SWI-Prolog -- Foreign debugging functions