How can I write actual strrchr function in C language?

Description Searches for the last occurrence of the character c (an unsigned char) in the string pointed to by the argument str. The terminating null character is considered to be part of the string. Returns a pointer pointing to the last matching character, or null if no match was found.

The function strrchr() is very simple to write in C: it suffices to iterate on the string, remembering the last position where the character was seen...

#include <string.h>

/* 7.24.5.5 The strrchr function */
char *strrchr(const char *s, int c) {
    const char *p = NULL;

    for (;;) {
        if (*s == (char)c)
            p = s;
        if (*s++ == '\0')
            return (char *)p;
    }
}