0_0_13486313_8424.c 0_0_13486313_8424.c(7) : error C2065: “sum”: 未声明的标识符 0_0_13486313_8424.c(9) : error C2065: “sum”: 未声明的标识符 0_0_13486313_8424.c(10) : error C2065: “sum”: 未声明的标识符