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Subject: Re: [boost] [clang][preprocessor] Testing of clang emualting the VC++ preprocessor on Windows
From: Edward Diener (eldiener_at_[hidden])
Date: 2016-04-05 20:12:16

On 4/5/2016 11:38 AM, degski wrote:
> Hi Andrey,
> Someone interested in clang on Windows has to get his hands dirty and make
>> that happen.
> Anybody interested in developping C/C++/Obj C on windows should be
> interested, it seems nobody is aware of Clang/LLVM on windows.

Clang on Windows is two different implementations. There is clang on
Windows targeting mingw(-64)/gcc and there is clang on Windows targeting

I have filed bugs in clang's bug tracker for clang on Windows targeting
mingw(-64)/gcc but I have not had time to investigate and file bug
reports for linking problems in this environment, which exist and can be
seen when building some Boost non-header only libraries as well as some
Boost executables for testing. I know what the basic problem is, which
is that clang is not providing the same object names and visibility as
gcc despite the fact that it uses the gcc linker. So linking sometimes
fails. But I have not had time to track down and report specific linking

As far as clang on Windows targeting VC++ a major problem is clearly
that clang's emulation of the VC++ preprocessor is failing. What you
expect Boost to do about this I do not know, but one thing this Boost
developer will not do is try to find workarounds for these failures. I
did ask on the clang mailing list how I can get clang targeting VC++ to
show the emulated expansion of macros that it was doing so I ( and
possibly others ) could at least report to clang the exact situations
where clang's emulation of the VC++ preprocessor was giving an error
whereas the VC++ preprocessor was working. The reaction I got for my
query was complete silence. In other words clang targeting VC++ appears
to be following the VC++ path of not only producing a non-standard
preprocessor but also making sure that no one can actually find out what
this non-standard preprocessor is actually doing when it erroneously
performs macro expansion. Therefore to me there is absolutely no point
of following clang down this path no matter how popular clang's
emulation of VC++ may turn out to be until the nonsense involving the
preprocessor is resolved. Many Boost libraries use the Boost PP for
preprocessor code so expecting these Boost libraries to work with clang
targeting VC++ is a waste of time.

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