0_0_29139510_1594.c 0_0_29139510_1594.c(5) : error C2065: “b”: 未声明的标识符 0_0_29139510_1594.c(6) : error C2065: “sum”: 未声明的标识符 0_0_29139510_1594.c(6) : error C2065: “b”: 未声明的标识符 0_0_29139510_1594.c(7) : error C2065: “sum”: 未声明的标识符