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

Subject: Re: [boost] [clang] How to use CLang for Windows?
From: Edward Diener (eldiener_at_[hidden])
Date: 2013-09-29 20:36:41

On 9/29/2013 6:17 PM, Chandler Carruth wrote:
> On Sun, Sep 29, 2013 at 4:43 PM, Beman Dawes <bdawes_at_[hidden]> wrote:
>
>> On Sun, Sep 29, 2013 at 4:06 PM, Edward Diener <eldiener_at_[hidden]
>>> wrote:
>>
>>>
>>> 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.