僅標頭的ANSI C庫怎么可能？

Question

有一個非常受歡迎的名為nuklear的庫， 它既是用ANSI C編寫的，也完全是標頭的。 但是，每個轉換單元中只能有一個函數定義，並且ANSI C沒有inline函數，那么該庫如何正常工作而沒有鏈接器錯誤？

Answer 1

從第73行開始，描述了如何使用此標頭：

/// ## 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，通常包括該頭文件只會給您聲明。 如果在包含之前#define NK_IMPLEMENTATION ，則包含實現。