Compilare: user.c: In function ‘main’: user.c:15:5: warning: format ‘%lu’ expects argument of type ‘long unsigned int *’, but argument 2 has type ‘size_t *’ [-Wformat=] scanf("%lu", &t); ^ user.c:60:9: warning: format ‘%lu’ expects argument of type ‘long unsigned int’, but argument 2 has type ‘size_t’ [-Wformat=] printf("%lu\n", i); ^ user.c:10:14: warning: unused variable ‘found’ [-Wunused-variable] char *p, found; ^ user.c:9:21: warning: unused variable ‘diff’ [-Wunused-variable] size_t t, i, q, diff, plen; ^ user.c:12:12: warning: ignoring return value of ‘freopen’, declared with attribute warn_unused_result [-Wunused-result] freopen("prefix.in", "r", stdin); ^ user.c:13:12: warning: ignoring return value of ‘freopen’, declared with attribute warn_unused_result [-Wunused-result] freopen("prefix.out", "w", stdout); ^ user.c:15:10: warning: ignoring return value of ‘scanf’, declared with attribute warn_unused_result [-Wunused-result] scanf("%lu", &t); ^ user.c:19:14: warning: ignoring return value of ‘fgets’, declared with attribute warn_unused_result [-Wunused-result] fgets(p, sizeof s, stdin); ^ In file included from /usr/include/stdio.h:934:0, from user.c:1: In function ‘fgets’, inlined from ‘main’ at user.c:19:14: /usr/include/i386-linux-gnu/bits/stdio2.h:253:2: warning: call to ‘__fgets_chk_warn’ declared with attribute warning: fgets called with bigger size than length of destination buffer [enabled by default] return __fgets_chk_warn (__s, __bos (__s), __n, __stream); ^