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Subject: Re: [boost] [clang] Using clang in Windows
From: Paul A. Bristow (pbristow_at_[hidden])
Date: 2014-07-15 05:01:26

> -----Original Message-----
> From: Boost [mailto:boost-bounces_at_[hidden]] On Behalf Of Edward Diener
> Sent: 14 July 2014 22:08
> To: boost_at_[hidden]
> Subject: Re: [boost] [clang] Using clang in Windows
> On 7/14/2014 1:35 PM, Paul A. Bristow wrote:
> >
> >
> >> -----Original Message-----
> >> From: Boost [mailto:boost-bounces_at_[hidden]] On Behalf Of
> >> Edward Diener
> >> Sent: 14 July 2014 08:06
> >> To: boost_at_[hidden]
> >> Subject: [boost] [clang] Using clang in Windows
> >>
> >> Just a note to everybody about using clang in Windows

> 2) The greater of the two problems is that in order to compile with the
> VC++ header files clang in Windows, targeting VC++, has had to emulate a
> certain amount of VC++ "bugs" just to digest the header files without compile
> The most serious negative form of this emulation IMO is that clang has
> some of the "bugs" in the very non-standard VC++ preprocessor. However the
> of the "bugs" in the VC++ preprocessor, even if the VC++ preprocessor "works"
> for the majority of fairly simple macro processing, is large when it comes to
the sort
> of preprocessor metaprogramming done in Boost PP and my own VMD library.
> These bugs all center around the fact that the VC++ preprocessor does not do
> expansion correctly, often seemingly not fully expanding macro input before
> tokens are substituted in the invoking macros output. But there are a number
> other things which the VC++ preprocessor gets wrong, which can only be
> by very complicated examples and rarely by easy cases. It is highly doubtful
> clang targeting VC++ duplicates all the "bugs" and preprocessing weirdness of
> macro expansion, but just duplicating some of them creates another compiler
> weird VC++ like problems which a library like Boost PP is asked to deal with.
I know
> Paul Mensonides has no enthusiasm for such work and neither do I, dealing with
> VC++ itself has been hard enough. I made the suggestion in the clang
> mailing list that clang targeting VC++ should act like the buggy VC++
> for macros in VC++'s header files but should be a C++ standard conforming
> preprocessor otherwise, possibly controlled by some pragmas, but it seems like
> nobody cares about this. There are just too many programmers who just want
> targeting VC++ to behave like VC++ so they can use it theirt VS IDE compiler
and they
> don't care if doing so means that it cannot compile other C++ standard code
> correctly, in this particular case C++ macros.

Thanks for your efforts on this can of worms too.

Perhaps we have to wait for Microsoft to produce an (presumably) optional
'correct' pre-processor?

This wait will not be what *you* want, of course!


Paul A. Bristow
Prizet Farmhouse
Kendal UK LA8 8AB
+44 01539 561830

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