behoffski wrote:

>          In file included from mbsstr.c:32:0:
>          str-kmp.h: In function 'knuth_morris_pratt':
>          str-kmp.h:35:1: error: stack protector not protecting local
> variables: variable length buffer [-Werror=stack-protector]
>           knuth_morris_pratt (const UNIT *haystack,
>           ^

These warnings don't indicate any bugs in the code; they're merely about 
incomplete run-time checking in the underlying implementation.  I was 
particularly amused by a refusal to compile a function on the grounds 
that its code doesn't use the stack!

So let's just disable the warnings.  I pushed the attached patch.

> Valgrind and -fsanitize=address are incompatible

Thanks, I didn't know that.  Too bad, but understandable.  Neither tool 
dominates the other, so I guess we'll have to use them separately.