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Re: Dealing with compilers that pretend to be GCC

On Fri, Jan 20, 2012 at 2:41 PM, Cary Coutant <> wrote:
>> Yeah, but it’s a shame that those compilers define __GNUC__ without
>> supporting 100% of the GNU C extensions. ?With this approach, you would
>> also need to add !defined for Clang, PGI, and probably others.
> Having worked on the other side for a while -- for a vendor whose
> compiler supported many but not all of GCC's extensions -- I claim
> that the problem is with the many examples of code out there that
> blindly test for __GNUC__ instead of testing for individual
> extensions. From the other vendor's point of view, it's nearly useless
> to support any of the GCC extensions if you don't also define
> __GNUC__, because most code out there will simply test for that macro.
> By defining the macro even if you don't support, for example, nested
> functions, you can still compile 99% of the code that uses the
> extensions.

If there were a defined way to test for extensions from within C (or
C++), then this problem would be much reduced. Clang has something of
a framework to query support for different features, and I drafted a
proposal for something similar that would work across different
compilers (with the intension of tracking C++11 features as they roll
out), but that proposal went nowhere (I was too late for it to be
useful for C++11 in any case).

-- James

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