View Compilation Error

0_0_27194764_15687.cpp: In function 'int main()':
0_0_27194764_15687.cpp:13:41: error: 'memset' was not declared in this scope
 #define mem(a, b) memset(a, b, sizeof(a))
                                         ^
0_0_27194764_15687.cpp:77:3: note: in expansion of macro 'mem'
   mem(gay, 0);
   ^