Compilare: user.cpp: In function ‘int main()’: user.cpp:130:9: warning: converting to non-pointer type ‘char’ from NULL [-Wconversion-null] c[m]=NULL; ^ user.cpp:128:27: warning: ignoring return value of ‘int fscanf(FILE*, const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] fscanf(f,"%d%d",&n,&m); ^ user.cpp:129:12: warning: ignoring return value of ‘char* gets(char*)’, declared with attribute warn_unused_result [-Wunused-result] gets(c); ^ user.cpp:133:20: warning: ignoring return value of ‘char* gets(char*)’, declared with attribute warn_unused_result [-Wunused-result] gets(c); ^ /tmp/ccr9cxLf.o: In function `main': user.cpp:(.text.startup+0x92): warning: the `gets' function is dangerous and should not be used.