__cdecl和__declspec调用约定混乱 [英] __cdecl and __declspec calling conventions confusion

问题描述

我正在为第三方应用程序编写DLL。首席软件工程师提到该应用程序使用__cdecl（/ Gd）调用约定。

I am writing a DLL for a third party application. The main software engineer mentions that the application uses the __cdecl (/Gd) calling convention. That I need to make sure that I use that.

此外，第三方还向我提供了一个C ++ DLL框架，该框架导出的功能如下：

Additionally, the third party has provided to me a C++ DLL skeleton which exports the functions as follows:

#ifdef _EXPORTING
  #define DECLSPEC    __declspec(dllexport)
#else
   #define DECLSPEC    __declspec(dllimport)
#endif

#ifdef __cplusplus
   extern "C" {  
#endif

DECLSPEC int ICD_Create(char* id);
....
....

我有点困惑。为什么使用__declspec约定而不是__cdedl导出函数？ __declspec支持_cdecl吗？

I am kind of confused. Why the functions are being exported using __declspec convention instead of __cdedl?? does __declspec support _cdecl?

谢谢。

推荐答案

__ declspec（）和 __ cdecl 解决了调用函数的两个不同方面，您可以（在这种情况下，通过

__declspec() and __cdecl are addressing two different aspects of calling the function, and you can (and in this case by the sounds of it you should) use both.

__ cdecl 指定调用约定，该约定指定如何将参数传递给函数通过堆栈，而且很重要的是，谁随后清理堆栈（在 __ cdecl 的情况下，是清理程序的调用方）。

__cdecl specifies the calling convention, which specifies how parameters are passed to the function via the stack, and, very importantly, who cleans up the stack afterwards (in the case of __cdecl it is the caller who tidies up).

__ declspec（dllimport / dllexport）用于简化从DLL导出函数的定义：您不需要使用它们，而另一个导出函数的方法非常笨拙。

__declspec(dllimport/dllexport) is used to simplify exporting function definitions from a DLL: you don't need to use them, but the other ways of exporting functions are quite klunky.

明确使用 __ cdecl 而不是做什么可能是一个好主意。您已完成的代码段，即依靠编译器选择调用约定。您可以使用我认为的命令行开关来覆盖它，并且我相信默认值会有所不同，具体取决于您是编译C还是C ++代码，因此（像往常一样）更明确是更好的选择。

It is probably a good idea to explicitly use __cdecl rather than doing what the code snippet you have has done, which is rely on the compiler to choose the calling convention. You can override this with command-line switches I think, and I believe the default is different depending on whether you are compiling C or C++ code, so more explicit is (as usual) better.

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