GCC编译时如何查询目标架构字节序？C++17跨编译器实现问询

以下实现完全基于编译器内置预定义宏，不需要构建系统参与，所有接口支持编译期求值，可直接用于constexpr上下文，适配GCC、Clang、MSVC三大主流编译器。

完整代码片段 #

#include <cstdint>

// 字节序枚举定义，与C++20 std::endian对齐，方便后续升级
enum class endian {
    little,
    big,
    mixed
};

// 编译器内置宏检测
#if defined(__GNUC__) || defined(__clang__)
#   if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
#       define PROJECT_ENDIAN_LITTLE 1
#   elif __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__
#       define PROJECT_ENDIAN_BIG 1
#   else
#       define PROJECT_ENDIAN_MIXED 1
#   endif
#elif defined(_MSC_VER)
// MSVC 默认为小端架构，仅特殊嵌入式/主机平台为大端
#   if defined(_M_AMD64) || defined(_M_IX86) || defined(_M_ARM) || defined(_M_ARM64)
#       define PROJECT_ENDIAN_LITTLE 1
#   else
#       define PROJECT_ENDIAN_BIG 1
#   endif
#else
#   error "Unsupported compiler, please add endian detection logic manually"
#endif

// 编译期查询接口
constexpr endian get_system_endian() noexcept {
#if defined(PROJECT_ENDIAN_LITTLE)
    return endian::little;
#elif defined(PROJECT_ENDIAN_BIG)
    return endian::big;
#else
    return endian::mixed;
#endif
}

// 便捷常量，直接用于编译期分支判断
constexpr bool is_little_endian = get_system_endian() == endian::little;
constexpr bool is_big_endian = get_system_endian() == endian::big;
constexpr bool is_mixed_endian = get_system_endian() == endian::mixed;

// 测试用例
#include <iostream>
int main() {
    // 编译期断言验证
    static_assert(!is_mixed_endian, "Mixed endian architecture is not supported");

    // C++17 if constexpr 编译期分支，无运行时开销
    if constexpr (is_little_endian) {
        std::cout << "Target architecture: little endian\n";
    } else {
        std::cout << "Target architecture: big endian\n";
    }
    return 0;
}

适配说明 #

• 支持编译器版本：GCC 5+, Clang 3.5+, MSVC 2017+
• 所有接口均为constexpr，可直接用于模板参数、static_assert等编译期场景
• 枚举定义与C20 std::endian 完全对齐，后续项目升级到C20可直接替换为标准库实现，无需修改业务代码

内容的提问来源于stack exchange，提问作者mcandre