Macro expansion ignores some tokens in MSVC-CodePudding

I have some problems with macro expansion in msvc compiler. I expect the following code to be expanded to F x, which it does on gcc and clang. But msvc expands it to just F ignoring x token. What's going on here?

#define S(s) s
#define F()

#define M() S(S(F) x)

M() // expands to 'F' on msvc

However, without defining F() it expands to F x on msvc too, as expected.

#define S(s) s
// #define F()

#define M() S(S(F) x)

M() // expands to 'F x' on msvc

I'm using Compiler Explorer site to check this code. Compiler version is x64 msvc v19.latest.

CodePudding user response：

Use /Zc:preprocessor to switch to the new, standard-conformant preprocessor. It behaves as you expect.