Compilare: user.cpp: In function ‘int main()’: user.cpp:33:18: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=0;i<strlen(r);i++) ^ user.cpp:37:32: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while(r[j]==' '&& j<=strlen(r)) ^ user.cpp:48:18: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=0;i<strlen(r);i++) ^ user.cpp:54:33: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while(r[k]==' ' && k<strlen(r)) ^ user.cpp:71:43: warning: passing NULL to non-pointer argument 2 of ‘void* memset(void*, int, size_t)’ [-Wconversion-null] memset(prod, NULL, sizeof prod); ^