将标头文件包含到标头文件中而不将其内容暴露给包含程序 [英] Including a header file into a header file without exposing it's content to the includer

问题描述

我想为C API写一个c ++包装器.为此，将C-API标头包含在我自己的标头中是最方便的，但这也将标头包含在外部系统的文件中，不应将其公开给C-API.

I would like to write a c++ wrapper for a C API. for this it is most convenient to just include the C-API header in my own header, but this also includes the header into the file of the outer system, that should not be exposed to the C-API.

capi.h

enum MyFlags {
    MY_FLAG_A,
    MY_FLAG_B,
};

void FOO_bar(int flags);

cppapi.hh

cppapi.hh

#include "capi.h"

enum class MyFlags { 
    A = MY_FLAG_A, 
    B = MY_FLAG_B 
};

namespace foo {
    void bar(MyFlags flags) { 
        FOO_bar((int)flags); 
    }
}

仅用于将c命名约定转换为c ++语言功能.因此，当使用该语言的C ++变体时，我希望c_api对我的自动完成不可用，因此不会被意外使用.

it is just to translate c naming convention into c++ language features. So when using the C++ variant of the language, I would like that the c_api is not available to my auto completion and therefore not accidently used.

推荐答案

在项目命名空间中定义命名空间 detail ，并在其中包含C标头.

Define a namespace detail in your projects namespace, and include the C header there.

如果C标头未包含在C ++中，则未定义en 外部"C" -块，请执行以下操作之一:

If the C header does not define en extern "C"- block when included from C++, do one of these:

• 用外部 extern"C" 块包装，并验证C标头(如果包含)是有效且等效的C ++.(特别注意枚举大小和内联函数).
• 使用 #ifdef __cplusplus 使它有效并等效于C ++.

• Wrap with an external extern "C" block and verify the C header is, if included thus, valid and equivalent C++. (Special attention to enum sizes and inline functions).
• Make it valid and equivalent C++ using #ifdef __cplusplus.

因此，所有这些C函数都隐藏在内部的实现详细信息命名空间中，不会打扰任何人.

Thus, all those C functions are hidden in the internal implementation-detail namespace, and won't bother anyone.

namespace foo {
    namespace internal {
        extern "C" {
            #include "capi.h"
        }
    }
    // Function alias
    using bar = internal::FOO_bar;
    // Type alias
    using config_t = internal::FOO_config;
}

使用 using 选择性地将所需的那些符号添加到 FOO -命名空间中.

Selectively get those symbols you need into the FOO-namespace using using.

顺便说一句:您的转发器功能实际上应该是 inline ！

BTW: Your forwarder-function should really be inline!

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