View Compilation Error

0_0_34519526_28744.cpp: In function 'int main()':
0_0_34519526_28744.cpp:6:38: error: 'memset' was not declared in this scope
 #define mem(x,y) memset(x,y,sizeof(x))
                                      ^
0_0_34519526_28744.cpp:38:3: note: in expansion of macro 'mem'
   mem(p,0);
   ^