Re: C23 compatibility question

Agile Developer wrote:
> I was wondering whether GNU objective-c, as implemented on top of C,
> supports C23 and if the objective-c implementation is interoperable
> with C23.

The default C standard when compiling Objective-C code with GCC is C89
so as Ethan said, you must specify -std=c23 or -std=gnu23.  Note that
there are some subtle bugs like these:

GCC rejects a "for" loop declaration for a variable named "in" as this
is reserved for fast enumeration (which works in C89 for Objective-C
only):
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=46473

GCC fails to recognize an ivar in a method implementation, confusing
it with an "if" variable declaration:
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=119117