Re: why does bsearch segfault on custom strcmp when qsort works fine?

On Thu, 15 Aug 2024 08:55:45 -0000 (UTC), Ike Naar wrote:

[snip]

The elements of the words array have type pointer-to-char.
So the first argument to bsearch should be the address of such an
element, that is,
a pointer-to-pointer-to-char and it should contain the adress of a
pointer to the first character of the oscar string.
Also, the value returned from bsearch should be interpreted as a
pointer-to-pointer-to-char.
 
    char * key = "oscar";
    char * * p = bsearch(&key, words, size, sizeof(char*), mystrcmp);
 

    index = p - words[0];
    found = p != NULL:

 
Two problems here: first, if bsearch returns NULL, the subtraction is
ill-defined.
Second, if bsearch returns non-null the index will be p - words, not p -
words[0];
 
    found = p != NULL:
    if (found) index = p - words;

Thank you! That solved the problem and clarified my mistakes.
By changing the code along the suggested lines it works great:

    char* s = "oscar";
    char** p = bsearch(&s, words, size, sizeof(char*), mystrcmp);
    if (p) {
        index = p - words;
        found = true;
    }