0_0_38987363_27914.c 0_0_38987363_27914.c(5) : error C2065: “sum”: 未声明的标识符 0_0_38987363_27914.c(8) : error C2065: “sum”: 未声明的标识符 0_0_38987363_27914.c(10) : error C2065: “sum”: 未声明的标识符