On 2023-11-01 23:13, Joseph Myers wrote:

> On Wed, 1 Nov 2023, peter0x44 via Gcc wrote:
> 
>> Why is #define used instead of typedef? I can't imagine how this could
>> possibly break any existing code.
> 
> That's how stdbool.h is specified up to C17.  In C23, bool is a keyword
> instead.

I see, I didn't know it was specified that way. It seems quite strange 
that typedef wouldn't be used for this purpose.

I suppose perhaps it matters if you #undef bool and then use it to 
define your own type? Still, it seems very strange to do this.

Maybe it's something to offer as a GNU extension? Though, I'm leaning 
towards too trivial to be worth it, just for a (very minor) improvement 
to a diagnostic that can probably be handled in other ways.