[cfe-dev] Clang inconsistency with gcc on Windows

[Yaron Keren]

Maybe gcc is more fogiving with checking redeclarations or some compiler
predefine is not the same. You can check this in depth by looking at
preprocess output (-E) and comparing how both compilers expand the
GetSystemTimeAsFileTime declaration.


2015-05-31 21:50 GMT+03:00 Edward Diener <eldlistmailingz at tropicsoft.com>:

> On 5/31/2015 2:05 PM, Yaron Keren wrote:
>
>> Boost tries to supplies its own version of the Windows API to avoid
>> including WIndows.h
>> Boost version of the API is not strictly identical to Windows.h, so if
>> Windows.h do get included somehow such errors happen. I always
>> -DBOOST_USE_WINDOWS_H to force Boost to use Windows.h instead of its own.
>>
>
> Thanks, that does work.
>
> I still would like to know why clang is giving errors in the situation I
> describe in my OP and gcc is not. I am not saying that clang is wrong to do
> so but clearly it is not being compatible with gcc in this area.
>
>
>>
>>
>> 2015-05-31 20:48 GMT+03:00 Edward Diener
>> <eldlistmailingz at tropicsoft.com
>> <mailto:eldlistmailingz at tropicsoft.com>>:
>>
>>
>>     Compiling some Boost library code the latest clang has produced an
>>     inconsistency with gcc on Windows that is making it impossible to
>>     build Boost libraries successfully.
>>
>>     The code in question, where clang is given an error:
>>
>>         clang-linux.compile.c++.without-pth
>>
>> ..\..\..\bin.v2\libs\context\build\clang-linux-3.7.0\debug\threading-multi\windows\stack_traits.obj
>>         In file included from
>>         ..\..\..\libs\context\src\windows\stack_traits.cpp:24:
>>         In file included from ..\..\..\boost/thread.hpp:13:
>>         In file included from ..\..\..\boost/thread/thread.hpp:12:
>>         In file included from ..\..\..\boost/thread/thread_only.hpp:15:
>>         In file included from
>>         ..\..\..\boost/thread/win32/thread_data.hpp:10:
>>         In file included from ..\..\..\boost/thread/thread_time.hpp:10:
>>         In file included from
>>         ..\..\..\boost/date_time/microsec_time_clock.hpp:23:
>>         ..\..\..\boost/date_time/filetime_functions.hpp:57:46: error:
>>         conflicting types for 'GetSystemTimeAsFileTime'
>>                  __declspec(dllimport) void __stdcall
>>         GetSystemTimeAsFileTime(FILETIME* lpFileTime);
>>                                                       ^
>>         /mingw/include\winbase.h:1397:24: note: previous declaration is
>> here
>>         WINBASEAPI void WINAPI GetSystemTimeAsFileTime(LPFILETIME);
>>
>>                               ^
>>
>>     and more of the same in many places building Boost libraries with
>> clang.
>>
>>     This is with the latest clang, which I build with mingw/gcc-4.8.1 on
>>     Windows.
>>
>>     With gcc-4.8.1:
>>
>>         gcc.compile.c++
>>
>> ..\..\..\bin.v2\libs\context\build\gcc-mingw-4.8.1\debug\threading-multi\windows\stack_traits.o
>>
>>
>>     With gcc-4.9.2
>>
>>         gcc.compile.c++
>>
>> ..\..\..\bin.v2\libs\context\build\gcc-mingw-4.9.2\debug\threading-multi\windows\stack_traits.o
>>
>>
>>     This is happening extensively in Boost code which uses the Windows
>>     API when compiling under Windows.
>>
>>     I do not know what WINBASEAPI is supposed to resove to under mingw,
>>     but clearly it should not be different for gcc and clang under
>>     Windows and gcc has no problems with this.
>>
>
>
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