View Compilation Error

0_0_21166317_29972.cpp: In function 'void foo()':
0_0_21166317_29972.cpp:13:35: error: 'memset' was not declared in this scope
 #define CLR(x) memset(x,0,sizeof x)
                                   ^
0_0_21166317_29972.cpp:46:3: note: in expansion of macro 'CLR'
   CLR(arr);
   ^