https://gcc.gnu.org/bugzilla/show_bug.cgi?id=120978
--- Comment #4 from Halalaluyafail3 <luigighiron at gmail dot com> --- (In reply to Andrew Pinski from comment #3) > (In reply to Andrew Pinski from comment #2) > > The C23 spec says: > > any token other than a parenthesis, a bracket, or a brace > > > > But # is not a token in C; it is only a preprocessor token ... > > I was wrong there, it is a C token but I suspect it is considered either the > `#` or `##` pp operator which case then would be invalid here. > And that is why GCC, EDG and MSVC all reject this because those 2 pp > operators are processed earlier than attribute processing. > > But I could be reading the spec wrong still. They are only considered operators during macro expansion. The standard provides the following example: > #define hash_hash # ## # > #define mkstr(a) # a > #define in_between(a) mkstr(a) > #define join(c, d) in_between(c hash_hash d) > char p[] = join(x, y); // equivalent to > // char p[] = "x ## y"; Which demonstrates that a ## token can be used (in this case stringized) without causing it to be treated as an operator.
