Compatibility with non-GNU compilers

最新推荐文章于 2025-01-07 00:07:52 发布

最新推荐文章于 2025-01-07 00:07:52 发布 · 103 阅读

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#C #C++ #C#

本文探讨了GCC中__attribute__机制的设计精妙之处及其在不同平台上的灵活使用方法。作者详细解释了如何通过预处理器定义使其在非GNU编译器环境中被忽略，并展示了这一机制在函数声明中的具体应用实例。

Fortunately, the __attribute__ mechanism was cleverly designed in a way to make it easy to quietly eliminate them if used on platforms other than GNU C. Superficially, __attribute__ appears to have multiple parameters (which would typically rule out using a macro), but the two sets of parentheses effectively make it a single parameter, and in practice this works very nicely.

/* If we're not using GNU C, elide __attribute__ */
#ifndef __GNUC__
#  define  __attribute__(x)  /*NOTHING*/
#endif

Note that __attribute__ applies to function declarations, not definitions, and we're not sure why this is. So when defining a function that merits this treatment, an extra declaration must be used (in the same file):

/* function declaration */
void die(const char *format, ...) __attribute__((noreturn))
                                  __attribute__((format(printf,1,2)));

void die(const char *format, ...)
{
	/* function definition */
}