Compilare: user.cpp: In function ‘int main()’: user.cpp:135: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result user.cpp:136: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result user.cpp:138: warning: ignoring return value of ‘char* fgets(char*, int, FILE*)’, declared with attribute warn_unused_result user.cpp: In function ‘std::list<char*, std::allocator<char*> > infix_to_postfix(char*)’: user.cpp:30: warning: ‘p’ may be used uninitialized in this function