Re: Feature request - a macro defined for GCC

[Chris Lattner <clattner at apple dot com>]

On Jul 3, 2008, at 10:01 AM, Andrew Haley wrote:

> Chris Lattner wrote:
>
> > IMO, the whole notion of a compiler-specific macro has pretty limited
> > usefulness.  Why not add macros for specific *features* offered by  
> > the
> > compiler.  For example:
> >
> > #ifdef __SUPPORTS_NESTED_FUNCTIONS__
> >
> > is much better than some mismash of version checking, which isn't
> > guaranteed to be right in the future.
>
> Yeah, but in the absence of an external specification of the syntax  
> it'd
> have to be __SUPPORTS_GNU_NESTED_FUNCTIONS__.

The feature names should be independent of the set of compilers that  
happen to implement them, that's the whole point.  Consider:

#ifdef __SUPPORTS_GNU_CXX_MIN_MAX_OPERATORS__

Mainline GCC doesn't support "GNU" min max operators!   GCC adds and  
removes extensions, and other compilers have good support for subsets  
of the GCC extensions.  Obviously if Intel is defining __GNUC__ with  
moderate success, then they implement whatever extensions the macro is  
guarding.

> Hmm, looks like this could
> get very messy, very quickly; I don't think you could do this in any
> effective way without some compiler-independent organization to define
> these macros.

Huh?  Why not?

-Chris