Compilare: main.cpp: In function 'int main()': main.cpp:21:27: warning: ignoring return value of 'int fscanf(FILE*, const char*, ...)', declared with attribute warn_unused_result [-Wunused-result] fscanf(fi,"%d %d",&n,&m); fgets(s1,nmax,fi); ^ main.cpp:21:47: warning: ignoring return value of 'char* fgets(char*, int, FILE*)', declared with attribute warn_unused_result [-Wunused-result] fscanf(fi,"%d %d",&n,&m); fgets(s1,nmax,fi); ^ main.cpp:29:24: warning: ignoring return value of 'char* fgets(char*, int, FILE*)', declared with attribute warn_unused_result [-Wunused-result] fgets(s1+1,nmax,fi); ^ In file included from /usr/include/stdio.h:936:0, from main.cpp:1: In function 'char* fgets(char*, int, FILE*)', inlined from 'int main()' at main.cpp:29:24: /usr/include/x86_64-linux-gnu/bits/stdio2.h:261:58: 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); ^