Re: [boost] [clang] How to use CLang for Windows?

30 Sep 2013

      On 9/29/2013 6:17 PM, Chandler Carruth wrote:
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On Sun, Sep 29, 2013 at 4:43 PM, Beman Dawes  wrote:
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On Sun, Sep 29, 2013 at 4:06 PM, Edward Diener 
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wrote:
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With all due respect, Beman, there is no point of doing this at least for
Boost headers once I reverted the fix to the Boost PP code that would
have
...
allowed clang under Windows to correctly compiler Boost PP code as a
strictly conforming C++ standard preprocessor. It fails miserably as the
VC++ preprocessor and I am not personally interested particularly in
discovering why since the VC++ preprocessor is just badly broken in a
number of respects general. To emulate that brokeness cannot be the goal
of
any C++ compiler.
IIUC, they are aiming to support the aspects of VC++ that are required to
compile and run the libraries shipped with Visual Studio and libraries like
Boost. I doubt they intend to mimic bugs not required for that purpose, and
they have stated up front that they intend to support all C++11/14
features, not just those supported by VC++.
Indeed. Boost.PP I think would likely be a prime candidate for explicitly
detecting Clang (even on Windows) and just doing the right thing.
The fix that I had made to Boost PP config.h, which I was asked to 
remove by Beman Dawes, explicitly detects that when _MSC_VER is defined 
and __clang__ is defined Boost PP should not treat the compiler as VC++. 
In the Boost PP config.h file prior to my fix if _MSC_VER is defined 
then the compiler is treated as VC++.

There are other cases in the Boost header files that assume that when 
_MSC_VER is defined the compiler is VC++ ( see my thread "Boost and 
clang under Windows" ) without checking if it could be another compiler 
emulating VC++. I had proposed in the aforementioned thread that I was 
willing to work on changing such code in other Boost libraries so that 
it did the correct thing when both _MSC_VER and __clang__ were defined, 
but the reaction of not only Mr. Dawes and others was that I should not 
do that so I desisted.