[cfe-dev] Clang on Windows targeting gcc requirements

Sat Jul 4 23:29:23 PDT 2015

clang uses its own *intrin.h files, found in ..\lib\clang\3.7.0\include\
relative to the bin, which appears before the gcc include directories. If
you run clang++ -v somefile.cpp you'll see which directory clang looks for,
it should look something like:

#include <...> search starts here:
 C:\mingw32\i686-w64-mingw32\include\c++
 C:\mingw32\i686-w64-mingw32\include\c++\i686-w64-mingw32
 C:\mingw32\i686-w64-mingw32\include\c++\backward
* C:\llvm\msvc\RelWithDebInfo\bin\..\lib\clang\3.7.0\include*
 C:\mingw32\lib\gcc\i686-w64-mingw32\4.9.1\include
 C:\mingw32\lib\gcc\i686-w64-mingw32\4.9.1\include-fixed
 C:\mingw32\i686-w64-mingw32\include
 C:\mingw32\include

2015-07-05 8:43 GMT+03:00 Edward Diener <eldlistmailingz at tropicsoft.com>:

> On 7/3/2015 10:59 AM, Yaron Keren wrote:
>
>> You only need to have the bin directory in your PATH. clang will find
>> the include and library directory based on the bin directory. There are
>> no fixed paths, you can put in c:\mingw or wherever.
>>
>
> I ran into a problem using mingw-64 and the latest clang. In the mingw-64
> intrin.h for gcc-4.9 on up it uses the gcc version number to decide whether
> to define the macro __MINGW_FORCE_SYS_INTRINS. If this macro is not defined
> it leads to multiple declarations for __m64 and some other CPU feature
> typdefs. Its gcc implementation defines __MINGW_FORCE_SYS_INTRINS for
> gcc-4.9 on up but clang still sets the gcc version number to gcc-4.2.1 so
> that __MINGW_FORCE_SYS_INTRINS is not automatically defined.
>
> My workaround for this was to define __MINGW_FORCE_SYS_INTRINS when using
> clang. This appears to work fine in my tests for clang but then I found a
> link of yours at
> http://lists.cs.uiuc.edu/pipermail/cfe-commits/Week-of-Mon-20141110/118349.html
> which appears to claim that defining __MINGW_FORCE_SYS_INTRINS forces the
> use of invalid CPU instructions when compiling with clang but evidently not
> when compiling with gcc.
>
> Does merely specifying all the x86-x64 compiler intrinsics, as the
> intrin.h in gcc-4.9 and up does, cause CPU instruction set problems when
> compiling with clang ? If so this means that I cannot use clang with
> gcc-4.9 and up unless I locally change their headers to avoid the problem.
> I have alerted mingw-64 about the general issue.
>
>
>>
>>
>> 2015-07-03 16:13 GMT+03:00 Edward Diener
>> <eldlistmailingz at tropicsoft.com
>> <mailto:eldlistmailingz at tropicsoft.com>>:
>>
>>     On 6/25/2015 2:13 PM, Yaron Keren wrote:
>>
>>         See http://reviews.llvm.org/D5268
>>         <
>> https://urldefense.proofpoint.com/v2/url?u=http-3A__reviews.llvm.org_D5268&d=AwMFaQ&c=8hUWFZcy2Z-Za5rBPlktOQ&r=CnzuN65ENJ1H9py9XLiRvC_UQz6u3oG6GUNn7_wosSM&m=ecMMp1TUmHLfiiZ_MlnPwTgmGQGZqkJoByqz4GWmOJ8&s=GyhTLhjqmvS-L0bXc8ytxxjhk6AnpKowj6eW2JYk9i4&e=
>> >
>>         <
>> https://urldefense.proofpoint.com/v2/url?u=http-3A__reviews.llvm.org_D5268&d=AwMFaQ&c=8hUWFZcy2Z-Za5rBPlktOQ&r=CnzuN65ENJ1H9py9XLiRvC_UQz6u3oG6GUNn7_wosSM&m=YgSrUuiAhPt76cF_h_LXb8Mg84W8p9nMvUiL3koHKP4&s=aW_6t6KDGfo5hO6NiTn5Hy9afNhzwfkX-BZHT9PtXmk&e=
>> >
>>
>>
>>     I can see that the patch has been applied officially to the latest
>>     clang source. It's in the latest code when I update llvm/clang.
>>     Thanks very much !
>>
>>     But how do I use it ?
>>
>>     Am I supposed to be able to build clang using a mingw-64 distro in
>>     my PATH ?
>>
>>     When I compile with clang how do I tell it to use the mingw-64
>>     headers and RTL ? Does it matter whether the mingw-64 distro is 32
>>     bit or 64 bit ?
>>
>>     Do I need to have the mingw-64 distro at c:\mingw ?
>>
>>     I am willing to test this for clang and report back results here,
>>     since I can easily switch between mingw-64 distros ( 4.8.4, 4.9.2,
>>     5.1 ) and I test a number of Boost libraries including my own with
>>     clang, but I need a little information on how to do it.
>>
>>
>>
>>
>>         2015-06-25 10:46 GMT+03:00 Edward Diener
>>         <eldlistmailingz at tropicsoft.com
>>         <mailto:eldlistmailingz at tropicsoft.com>
>>         <mailto:eldlistmailingz at tropicsoft.com
>>
>>         <mailto:eldlistmailingz at tropicsoft.com>>>:
>>
>>
>>              For either the latest clang built from souce on Windows or
>>         a binary
>>              distribution of clang on Windows it appears that clang
>>         expects the
>>              supporting gcc include files and lib files to be in the
>>         hardcoded
>>              directory:
>>
>>              c:\mingw
>>
>>              and follow the mingw directory structure.
>>
>>              1) Can this please be changed in the future so that some
>>         environment
>>              variable ( maybe CLANG_GCC ) can be set to the gcc
>> installation
>>              rather than use a hardcoded path ?
>>
>>              2) Can clang be updated to support the mingw-64 directory
>>         structure
>>              and not just the mingw directory structure ? The mingw-64
>>         distros
>>              seem now to be the preferred gcc distributions on Windows and
>>              support the latest versions of gcc.
>>
>>              Do I need to make these suggestions on the clang bug
>>         tracker for the
>>              suggestions to be seriously considered ?u
>>
>>
>>
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>>
>>
>>
>>
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>
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