Compilare: user.cpp: In function ‘int main()’: user.cpp:74: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result user.cpp:74: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result user.cpp:75: warning: ignoring return value of ‘char* gets(char*)’, declared with attribute warn_unused_result user.cpp:75: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result user.cpp:83: warning: ignoring return value of ‘char* gets(char*)’, declared with attribute warn_unused_result user.cpp:93: warning: ‘tmp_patt.P_t::x’ may be used uninitialized in this function user.cpp:93: warning: ‘tmp_patt.P_t::y’ may be used uninitialized in this function In file included from /usr/include/stdio.h:910, from /usr/include/c++/4.4/cstdio:45, from user.cpp:1: In function ‘char* gets(char*)’, inlined from ‘int main()’ at user.cpp:83: /usr/include/bits/stdio2.h:230: warning: call to ‘__gets_warn’ declared with attribute warning: please use fgets or getline instead, gets can't specify buffer size /tmp/ccH2ZBbT.o: In function `main': user.cpp:(.text+0x55a): warning: the `gets' function is dangerous and should not be used. user.cpp:(.text+0x4b6): warning: the `gets' function is dangerous and should not be used.