My issue stands unresolved. I simply did not realize that what I take issue with is the way the site handles both cases of invalid memory access and infinite loops.

as B1ts said, your code performs out-of-bounds accesses when strlen(str2) >= 9, because i > 0 is then always true as you keep incrementing i. Please use the question label to ask for help next time.

First of all, the error is coming from your code. I have no idea what's happening in your solution, but the part for(size_t i = (strlen(str2)-1)/8; i > 0; ++i){ is clearly wrong and will lead to invalid memory access errors.

You should format your solution next time, because this is unreadable. See https://docs.codewars.com/references/markdown/#code-block

Keeps showing an error due to signal 11. Does not show any console output, even from printing on the first line of function or test.