Hey folks,

[[foo(#)]] is a valid attribute in C, but invalid in C++, as # is
considered a token in C and a preprocessing-operator in C++
(The grammar of attributes expects tokens in both languages)

Is this divergence intended? It does not seem desirable.

Note that there is implementation divergence amongst C++ compilers here,
Clang accepts in all language modes, GCC rejects in all language modes
https://godbolt.org/z/Wj5fqdd1x

Cheers!

https://eel.is/c++draft/lex.operators#1
https://eel.is/c++draft/lex.token#nt:token
https://eel.is/c++draft/dcl.attr#nt:balanced-token