How to generate deprecated warning for a method in a COM interface (c++)

Question

We are using a "COM-like" model where I work, as we generally follow COM rules, but do not perform MIDL compiling and do not target other languages than c/c++. As such, I know I can always bend the rules to suit my needs, but I try not to since we might want to become truly COM-compliant someday and if that day comes, we want it to be as painless as possible. I want to print out a warning when anyone compiles code using a certain method from a specific interface. In c++ (we only support Microsoft compiler), we would add `__declspec(deprecated)` before the function declaration to achieve our goal. Can I just add this in front of my interface method declaration or is there a better, more COM way to do that? I would also like to know if only adding `__declspec(deprecated)` in front of the method is enough to force users to recompile (I would like to avoid that, if possible). Thanks Update I tried using `__declspec(deprecated)` in front of my method declaration like this: ``` struct Inter…

Accepted Answer

`__declspec(deprecated)` is a source-level feature of the MS C/C++ compiler, and won't affect the binary layout (ABI) of anything - so users will not have to recompile. The effect is to issue a compile-time warning to anyone calling that method via including your C++ header file. It will have no effect on people using your object as a COM object without including your header, e.g. from another language. I don't believe COM/IDL provides an analogous 'deprecated' attribute itself.

So in summary, you may as well add the attribute for the benefit of the C++ users, but if you ever provide for general COM consumers, they will have to rely on documentation you provide to know that the method is deprecated.

How to generate deprecated warning for a method in a COM interface (c++)

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