Re: Feature request - a macro defined for GCC

On Jul 3, 2008, at 3:01 PM, Joseph S. Myers wrote:
>> Taking an approach reduces startup time of the preprocessor,
>> because it
>> doesn't have to populate the identifier table with tons of
>> predefines.
>
> I'd hope this is not a significant cost (certainly not compared to the
> thousands of built-in functions on some target), though I haven't seen
> recent figures for startup costs.

I was referring to clang startup times, not GCC. clang registers
builtins completely lazily, so they don't take significant time at
startup. Much of clang startup time is populating the predefined
identifier table for macros.

> We have some existing practice for feature macros
> (__GNUC_GNU_INLINE__,
> __GNUC_STDC_INLINE__, __GCC_HAVE_SYNC_COMPARE_AND_SWAP_1, ...).

Understood. Likewise many system headers have these. I don't think
we can eliminate existing macros, but adding a plethora of new macros
would be bad.

-Chris