如何在 C++ 中使用 C 标头程序？
我正在 Visual Studio 2010 中开发一个项目，该项目将生成一个 win 32 dll 文件。我的例子是 C 文件，编译并运行良好。我想合并我编写的 C++ 函数中的一些功能，但遇到了一些困难。
如果我尝试将 C++ 函数链接到 C 程序，它对字符串等一无所知，并且根本不起作用（当然）。
所以我只能将示例更改为 C++ 程序，然后我就可以不受惩罚地使用其他文件了。当我尝试执行此操作时，我收到一个我不理解的链接错误，并且不确定如何解决。
这些示例使用供应商提供的标头，其中包括诸如以下语句
typedef void ( __cdecl *BINDING_PROC_BEVNT)(WORD_T choice, INT_T * pStatus,
I_EVNT_T * pIn, O_EVNT_T * pOut);
在主代码正文中，遵循示例：
extern BINDING_PROC_BEVNT b_evnt;
然后允许您编写
b_evnt(choice, &status, &inpEvent, &outpEvent);
在供应商提供的 C 文件中，这些再次引用为：
BINDING_PROC_BEVNT b_evnt;
b_evnt = (BINDING_PROC_BEVNT)GetProcAddress(hCNCMod, "bevnt");
我看到的链接器错误是：
错误 LNK2001：无法解析的外部符号“void (__cdecl* b_evnt)(unsigned Short,short *,union I_EVNT_T *,union O_EVNT_T *)”(?b_evnt@@3P6AXGPAFPATI_EVNT_T@@PATO_EVNT_T@@@ZA)
如果我重命名我的主文件并且重新编译为 C 程序，并省略我的 C++ 函数，一切完美编译。即使主文件被处理为 C++ 文件，Intellisense 似乎也能识别定义（将鼠标悬停在上方会显示正确的定义）。
此外，我尝试将 extern "C" 添加到几个不同的位置，但它似乎对 C++ 文件没有影响，并且在 C 文件中生成了编译错误（关于不了解字符串）。
任何见解都会受到赞赏，我今天可能只是盯着这个问题太久而没有发现一些明显的东西，或者它可能是我完全不知道的东西。
感谢您的帮助！
I am working on a project in Visual Studio 2010 which is to produce a win 32 dll file. The examples I have are C files and the compile and work well. I would like to incorporate some functionality from C++ function I've written but I have hit a bit of a wall.
If I attempt to link the C++ functions to the C program, it knows nothing about strings, etc and just doesn't work at all (of course).
So I am left with changing the example into a C++ program, then I can use my other files with impunity. When I attempt to do this I get a link error that I don't understand and am uncertain about how to resolve.
The examples use vendor provided headers, which include statements such as
typedef void ( __cdecl *BINDING_PROC_BEVNT)(WORD_T choice, INT_T * pStatus,
I_EVNT_T * pIn, O_EVNT_T * pOut);
In the body of the main code, following the examples:
extern BINDING_PROC_BEVNT b_evnt;
Which then allows you to write
b_evnt(choice, &status, &inpEvent, &outpEvent);
In a vendor provided C file, these are again referenced as:
BINDING_PROC_BEVNT b_evnt;
b_evnt = (BINDING_PROC_BEVNT)GetProcAddress(hCNCMod, "bevnt");
The linker error I am seeing is:
error LNK2001: unresolved external symbol "void (__cdecl* b_evnt)(unsigned short,short *,union I_EVNT_T *,union O_EVNT_T *)" (?b_evnt@@3P6AXGPAFPATI_EVNT_T@@PATO_EVNT_T@@@ZA)
If I rename my main file and recompile as a C program, and omit my C++ functions, everything compiles perfectly. Even when the main file is processed as a C++ file, Intellisense seems to recognize the definitions (hovering over shows the correct definitions).
Additionally I attempted to add extern "C" to a few different locations but it didn't seem to make a difference in the C++ files, and generated a compile error in the C files (about not knowing about strings).
Any insight would be appreciated, I may have simply stared at this too long today to be picking up on something obvious, or it may be something I'm completely unaware of.
Thanks for the help!
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如果您正在针对具有 C 语言绑定的库进行编译，则必须明确告诉 C++ 该库的头文件引用 C 对象，而不是 C++ 对象，否则 C++ 名称修改将阻止正确链接。通常您可以这样做：
这将告诉 C++ 编译器大括号之间的符号是 C 符号，并且不应应用名称修饰。
If you are compiling against a library that has C-language bindings, you have to tell C++ explicitly that the header files for the library reference C-objects, not C++ objects, or C++ name mangling will prevent correct linking. Often you can do this like so:
This will tell the C++ compiler that the symbols between the braces are C symbols, and should not have name mangling applied.
要包含 C++ 中的 C 头文件，请执行以下操作：
test.cpp
听起来您可能需要执行上述操作才能将供应商头文件包含在 C++ 代码中。
相关地，要使头文件自动适用于 C 和 C++：
c_header_file.h
并非所有供应商提供的头文件都包含上述
__cplusplus检测，因此您必须将它们手动包装在extern "C"如第一个示例所示。To include a C header file from C++, do something like this:
test.cpp
It sounds like the above is what you might need to do to include the vendor header file in your C++ code.
Relatedly, to make a header file automatically work for both C and C++:
c_header_file.h
Not all vendor-provided header files will contain the above
__cplusplusdetection, so you will have to wrap them manually inextern "C"as in the first example.这意味着无法找到 C++ 损坏的变量 b_evnt。这是真的，因为它应该被 C 破坏（只是一个 _ 前缀）。要解决这个问题，请在编译 C++ 时在标头中告诉编译器：
如果仅此而已，那么您就完成了。如果您需要更多符号，您可能想使用 Greg 的解决方案 - 但请注意，这也不是解决所有问题的方法。
That means, the C++ mangled variable b_evnt can't be found. That's true, because it should've been C mangled (just an _ prefix). To fix that, tell it to the compiler in the header when compiling for C++:
If that's all, you're done. If there are more symbols you need, you might want to use Greg's solution instead - but be aware that that is also not a fixall.
您的供应商提供的标头包含在 C++ 编译单元中，但它们没有为 C++ 做好准备。因此，函数的声明正在使用名称修改进行编译，C++ 编译器需要支持重载。
标头需要包装在
extern "C" {}块中，以便让 C++ 编译器知道这些声明使用 C 链接。可能最简单的方法是使用您自己的包装器标头，执行以下操作：
并包含 yiour 包装器标头而不是供应商的标头 - 包装器将适用于 C 或 C++ 编译。
另外，请联系您的库供应商并让他们知道他们应该进行这些更改 - 库的用户不必执行此解决方法即可使用 C++ 中的库。
Your vendor provided headers are being included in a C++ compilation unit, but they aren't prepared for C++. So the declarations of the functions are being compiled with name mangling the C++ compielr requires to support overloading.
The headers need to be wrapped in an
extern "C" {}block to let the C++ compiler know that these declarations use a C linkage.Probably the easiest way to do this it to use your own wrapper headers that do something like:
And include yiour wrapper header instead of the vendor's header - the wrapper will work for wither C or C++ compiles.
Also, contact your library vendor and let them know they should make these changes - users of the library shouldn't have to do this workaround to use the library from C++.