#include <stdio.h>
#include <stddef.h>

const char *strrchar(const char *src, char ch) {
    if (!src) return NULL;

    const char* res = NULL;
    for (;; ++src) {
    	if (*src == ch)
    		res = src;
    	if (*src == '\0')
    		break;
    }

    return res;
}

int main(void) {
    const char *s = "testtest";
    printf("%s\n", strrchar(s,'s'));
    
    return 0;
}