Re: [PATCH] cpp: new built-in __EXP_COUNTER__

[Kaz Kylheku <kaz@kylheku.com>]

On 2024-03-18 00:30, Jonathan Wakely wrote:
>>+@item __EXP_COUNTER__
>>+This macro's name means "(macro) expansion counter".
>>+Outside of macro replacement sequences, it expands to the integer
>>+token @code{1}.  This make it possible to easily test for the presence
>>+of this feature using conditional directives such as
>>+@code{#if __EXP_COUNTER__}.
> 
> It's a macro, so you can just use '#ifdef __EXP_COUNTER__' to test if
> it's supported. Is this additional behaviour necessary?

Thanks for looking at the patch.

The macro has to be defined, but it doesn't have to be 1.

Outside a macro body, it could just appear defined
with an empty value, as if by #define __EXP_COUNTER__.

When I dump the predefined macros of a nearby GCC installation, I
see very few empty ones:

   $ echo | gcc -dM -E - | awk 'NF == 2'
   #define __USER_LABEL_PREFIX__
   #define __REGISTER_PREFIX__

The __EXP_COUNTER__ and __UEXP_COUNTER__ symbols are
intended for suffix and infix use, so they are roughly in
a kind of category with those those two.

I will make that change, and also fix the grammar error
and remove the conflict-promoting ChangeLog changes.