gsm.cpp: In function 'int main()': gsm.cpp:162: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result gsm.cpp:163: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result gsm.cpp:165: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result gsm.cpp:167: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result gsm.cpp:169: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result gsm.cpp:170: warning: 'pz' may be used uninitialized in this function