C条件编译技术条件编译允许根据编译时条件选择性地包含或排除代码。这对于跨平台开发、调试版本控制和特性开关非常有用。#ifdef和#ifndef用于检查宏是否已定义。#include#define DEBUG_MODE#define FEATURE_LOGGINGvoid conditional_compilation_basic() {#ifdef DEBUG_MODEstd::cout Debug mode is enabled\n;#endif#ifndef RELEASE_MODEstd::cout Not in release mode\n;#endif#ifdef FEATURE_LOGGINGstd::cout Logging feature is enabled\n;#endif}#if、#elif和#else提供更复杂的条件判断。#define VERSION 2void version_specific_code() {#if VERSION 1std::cout Running version 1 code\n;#elif VERSION 2std::cout Running version 2 code\n;#elsestd::cout Running default version code\n;#endif}defined运算符检查宏是否已定义。void defined_operator() {#if defined(DEBUG_MODE) defined(FEATURE_LOGGING)std::cout Both debug and logging enabled\n;#endif#if defined(DEBUG_MODE) || defined(VERBOSE_MODE)std::cout Either debug or verbose mode\n;#endif}平台特定代码使用预定义宏。void platform_specific() {#ifdef _WIN32std::cout Windows platform\n;#elif defined(__linux__)std::cout Linux platform\n;#elif defined(__APPLE__)std::cout macOS platform\n;#elsestd::cout Unknown platform\n;#endif}编译器特定代码适配不同编译器。void compiler_specific() {#ifdef __GNUC__std::cout GCC compiler version: __GNUC__ . __GNUC_MINOR__ \n;#endif#ifdef _MSC_VERstd::cout MSVC compiler version: _MSC_VER \n;#endif#ifdef __clang__std::cout Clang compiler\n;#endif}调试代码可以通过条件编译控制。#ifdef DEBUG_MODE#define DEBUG_PRINT(x) std::cout [DEBUG] x \n#else#define DEBUG_PRINT(x)#endifvoid debug_code() {int value 42;DEBUG_PRINT(Value: value);#ifdef DEBUG_MODEstd::cout Additional debug information\n;#endif}特性开关控制功能的启用和禁用。#define ENABLE_FEATURE_A#undef ENABLE_FEATURE_Bvoid feature_flags() {#ifdef ENABLE_FEATURE_Astd::cout Feature A is enabled\n;#endif#ifdef ENABLE_FEATURE_Bstd::cout Feature B is enabled\n;#elsestd::cout Feature B is disabled\n;#endif}条件编译可以优化不同配置的代码。#ifdef OPTIMIZE_FOR_SPEED#define BUFFER_SIZE 4096#define USE_CACHE true#else#define BUFFER_SIZE 1024#define USE_CACHE false#endifvoid optimization_config() {char buffer[BUFFER_SIZE];std::cout Buffer size: BUFFER_SIZE \n;std::cout Cache enabled: USE_CACHE \n;}条件编译是管理代码变体和平台差异的重要工具。