Compilare: user.cpp: In function ‘int main()’: user.cpp:18:9: warning: converting to non-pointer type ‘char’ from NULL [-Wconversion-null] c[n]=NULL,n--; ^ user.cpp:16:22: warning: ignoring return value of ‘char* fgets(char*, int, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] fgets(c+1,5010,f); ^ In file included from /usr/include/stdio.h:936:0, from user.cpp:1: In function ‘char* fgets(char*, int, FILE*)’, inlined from ‘int main()’ at user.cpp:16:22: /usr/include/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); ^