仅标头的ANSI C库怎么可能？

Question

有一个非常受欢迎的名为nuklear的库， 它既是用ANSI C编写的，也完全是标头的。 但是，每个转换单元中只能有一个函数定义，并且ANSI C没有inline函数，那么该库如何正常工作而没有链接器错误？

Answer 1

从第73行开始，描述了如何使用此标头：

/// ## Usage
/// This library is self contained in one single header file and can be used either
/// in header only mode or in implementation mode. The header only mode is used
/// by default when included and allows including this header in other headers
/// and does not contain the actual implementation. <br /><br />
///
/// The implementation mode requires to define  the preprocessor macro
/// NK_IMPLEMENTATION in *one* .c/.cpp file before #includeing this file, e.g.:
///
/// ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~C
///     #define NK_IMPLEMENTATION
///     #include "nuklear.h"
/// ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

因此，通常包括该头文件只会给您声明。 如果在包含之前#define NK_IMPLEMENTATION ，则包含实现。