C语言基础（L17）条件编译

条件编译，可控程序流程

#include <stdio.h>#ifdef DEBUG    #define LOG(s) printf("[%s:%d] %s\n", __FILE__, __LINE__, s)#else    #define LOG(s) NULL#endif#ifdef HIGHvoid f(){    printf("This is the high level product!\n");}#elsevoid f(){}#endifint main(){    LOG("Enter main() ...");        f();        printf("1. Query Information.\n");    printf("2. Record Information.\n");    printf("3. Delete Information.\n");        #ifdef HIGH    printf("4. High Level Query.\n");    printf("5. Mannul Service.\n");    printf("6. Exit.\n");    #else    printf("4. Exit.\n");    #endif        LOG("Exit main() ...");        return 0;}