MIDL(常量)参考 [英] MIDL (Constant) References

问题描述

MIDL方法声明中没有常量引用吗??

Are there no constant references in MIDL method declarations????

例如

[id(1), helpstring("My Method")]
HRESULT MyMethod(
    [in] IID & const rclsid
);

为

HRESULT MyMethod(
    IID const &rclsid
);

推荐答案

MIDL并不真正支持参考参数，它仅支持"in"和"out"参数.因此，如果您确实传递了引用，则它只是指向该值的指针的语法糖(问题是可观察性-如果您在我们的方法签名中具有回调函数或接口，则可以从回调中观察到对引用的更改，但是在函数返回之前，对[out]参数的更改是不可见的.

MIDL doesn't really support reference parameters, it only supports "in" and "out" parameters. So if you DO pass in a reference, it's just syntactic sugar for a pointer to the value (the issue is observability - if you have a callback function or interface in our method signature, changes to a reference would be observable from the callback, but changes to an [out] parameter aren't visible until the function returns.

此外，& const"和"const&"之间的区别迷路了.如果您查看REFGUID的定义，您会发现它们仅对C ++代码使用一种形式的"const":

In addition, the difference between "& const" and "const &" are lost. If you look at the definition of REFGUID, you'll see that they only use one form of "const" for C++ code:

#ifdef __midl_proxy
#define __MIDL_CONST
#else
#define __MIDL_CONST const
#endif

#ifndef _REFGUID_DEFINED
#define _REFGUID_DEFINED
#ifdef __cplusplus
#define REFGUID const GUID &
#else
#define REFGUID const GUID * __MIDL_CONST
#endif
#endif

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