typedef int ssize_t;
typedef unsigned int size_t;

int test(int fd, ssize_t (*callback)(int, const void *, size_t));
int test2(int fd, int (*callback)(int, const void *, int));

#include "apue.h"

int test(int fd, ssize_t (*callback)(int, const void *, size_t)) {

}

int test2(int fd, int (*callback)(int, const void *, int)) {

}

#include "apue.h"

ssize_t callback(int a, const void *b, size_t c) {
    return 0;
}

int callback2(int a, const void *b, int c) {
    return 0;
}

int main(void) {
    test(1, callback); // Go to Definition failed. (Only jumped to the Declaration)
    test2(1, callback2); // Go to Definition works fine.
}