1#define _FILE_OFFSET_BITS 64
2#include <unistd.h>
3#include <fcntl.h>
4#include <stdio.h>
5#include <resolv.h>
6
7int main() {
8 /* in glibc 2.28+ and _FILE_OFFSET_BITS=64 fcntl is #define'd to fcntl64
9 * Thus headers say `fcntl64` exists, but libc.so.6 (the old one)
10 * disagrees, resulting in a linking error unless headers are made
11 * backwards-compatible.
12 *
13 * Glibc 2.28+:
14 * FUNC GLOBAL DEFAULT UND fcntl64@GLIBC_2.28 (3):
15 *
16 * Glibc 2.27 or older:
17 * FUNC GLOBAL DEFAULT UND fcntl@GLIBC_2.2.5
18 */
19 printf("address to fcntl: %p\n", fcntl);
20
21 /* The following functions became symbols of their own right with glibc
22 * 2.34+. Before 2.34 resolv.h would #define res_search __res_search; and
23 * __res_search is a valid symbol since the beginning of time.
24 *
25 * On glibc 2.34+ these symbols are linked this way:
26 * FUNC GLOBAL DEFAULT UND res_search@GLIBC_2.34 (2)
27 *
28 * Pre-glibc 2.34:
29 * FUNC GLOBAL DEFAULT UND __res_search@GLIBC_2.2.5 (4)
30 */
31 printf("address to res_search: %p\n", res_search);
32 printf("address to res_nsearch: %p\n", res_nsearch);
33 printf("address to res_query: %p\n", res_query);
34 printf("address to res_nquery: %p\n", res_nquery);
35 printf("address to res_querydomain: %p\n", res_querydomain);
36 printf("address to res_nquerydomain: %p\n", res_nquerydomain);
37 printf("address to dn_skipname: %p\n", dn_skipname);
38 printf("address to dn_comp: %p\n", dn_comp);
39 printf("address to dn_expand: %p\n", dn_expand);
40}