Compilare: user.cpp: In function ‘int main()’: user.cpp:21:23: warning: format ‘%s’ expects argument of type ‘char*’, but argument 2 has type ‘char (*)[2000010]’ [-Wformat=] scanf("%s%s",&a,&b); ^ user.cpp:21:23: warning: format ‘%s’ expects argument of type ‘char*’, but argument 3 has type ‘char (*)[2000010]’ [-Wformat=] user.cpp:26:9: warning: converting to non-pointer type ‘char’ from NULL [-Wconversion-null] a[0]=NULL; ^ user.cpp:29:9: warning: converting to non-pointer type ‘char’ from NULL [-Wconversion-null] b[0]=NULL; ^ user.cpp:18:37: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("strmatch.in","r",stdin); ^ user.cpp:19:39: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("strmatch.out","w",stdout); ^ user.cpp:21:24: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%s%s",&a,&b); ^