View Compilation Error

0_0_17704138_10217.cpp: In constructor 'ST::ST(std::vector<int>&)':
0_0_17704138_10217.cpp:18:38: error: 'memset' was not declared in this scope
 #define CLR(a) memset(a, 0, sizeof(a))
                                      ^
0_0_17704138_10217.cpp:74:9: note: in expansion of macro 'CLR'
         CLR(val);
         ^