Compilare: main.c: In function 'main': main.c:38:5: warning: ignoring return value of 'fgets', declared with attribute warn_unused_result [-Wunused-result] fgets(s1, 20000000, fin); ^~~~~~~~~~~~~~~~~~~~~~~~ main.c:40:5: warning: ignoring return value of 'fgets', declared with attribute warn_unused_result [-Wunused-result] fgets(s2, 20000000, fin); ^~~~~~~~~~~~~~~~~~~~~~~~ In file included from /usr/include/stdio.h:936:0, from main.c:1: In function 'fgets', inlined from 'main' at main.c:38:5: /usr/include/x86_64-linux-gnu/bits/stdio2.h:261:9: warning: call to '__fgets_chk_warn' declared with attribute warning: fgets called with bigger size than length of destination buffer return __fgets_chk_warn (__s, __bos (__s), __n, __stream); ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ In function 'fgets', inlined from 'main' at main.c:40:5: /usr/include/x86_64-linux-gnu/bits/stdio2.h:261:9: warning: call to '__fgets_chk_warn' declared with attribute warning: fgets called with bigger size than length of destination buffer return __fgets_chk_warn (__s, __bos (__s), __n, __stream); ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~