[llvm-dev] LLVM 3.7.0 build errors on Windows

[Ben Swift via llvm-dev]

I'm working on a cross-platform project which links (statically) against
LLVM, which I use for MCJIT purposes.

Everything was fine on 3.4.2. I'm just experimenting with upgrading to
3.7.0, and everything works fine on OSX & Linux once I changed my
project to reflect the API updates.

On Windows, I get a bunch of compile errors - hundreds of them, but
variations on a couple of different themes, such as

Error C3805 '(': unexpected token, expected either '}' or a ','
llvm\Support\COFF.h 168
Error C3646 'Checksum': unknown override specifier
llvm\Object\COFF.h 50
Error C4430 missing type specifier - int assumed. Note: C++ does not
support default-int llvm\Object\COFF.h 52

All the errors are reported in LLVM header files, mostly
llvm/Support/COFF.h and llvm/Object/COFF.h

I'm using Visual Studio Community 2015, the CXX compiler identification
is MSVC 19.0.23026.0

My CPP includes are:

WIN32
_WINDOWS
NDEBUG
_CRT_SECURE_NO_DEPRECATE
_CRT_SECURE_NO_WARNINGS
_CRT_NONSTDC_NO_DEPRECATE
_CRT_NONSTDC_NO_WARNINGS
_SCL_SECURE_NO_DEPRECATE
_SCL_SECURE_NO_WARNINGS
__STDC_CONSTANT_MACROS
__STDC_FORMAT_MACROS
__STDC_LIMIT_MACROS
_GNU_SOURCE
%(PreprocessorDefinitions)

Now, a couple of things are suspicious:

- in googling around it seems like there are some problems with
including Windows.h (which I have to include for other reasons) as well
as the LLVM headers, at least with previous versions of LLVM.
- on OSX, I did have to add a -std=c++11 flag before it would compile.
But I thought I didn't need/couldn't do that on Windows?

Does anyone have any idea what might be the problem, or ideas for
solutions/workarounds?

Cheers
Ben
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[Renato Golin via llvm-dev]

On 3 September 2015 at 02:02, Ben Swift via llvm-dev

<llvm...@lists.llvm.org> wrote:
> Does anyone have any idea what might be the problem, or ideas for
> solutions/workarounds?

Hi Ben,

We have moved up the minimum version of most compilers, but AFAIK,
MSVC 2015 is supported. Maybe you do need -std=c++11 after all. Have
you tried that?

cheers,
--renato

[Russell Wallace via llvm-dev]

I have the same setup as you, and it's working fine, but I think that's because I have #include <windows.h> after the llvm headers. I tried moving it before them just now and I get the same error messages as you. I also took a look at C:\llvm\tools\clang\lib\Driver\MSVCToolChain.cpp and it likewise puts the windows header after the llvm headers. Can you move it to after?

[Nico Rieck via llvm-dev]

On 03.09.2015 10:28, Russell Wallace via llvm-dev wrote:
> I have the same setup as you, and it's working fine, but I think that's
> because I have #include <windows.h> after the llvm headers. I tried moving
> it before them just now and I get the same error messages as you. I also
> took a look at C:\llvm\tools\clang\lib\Driver\MSVCToolChain.cpp and it
> likewise puts the windows header after the llvm headers. Can you move it to
> after?

Support/COFF.h is incompatible with winnt.h because the former defines
the IMAGE_* constants as enums while the latter uses macros. If you
cannot avoid including both headers in the same TU you have to undef
those macros.

-Nico

[Reid Kleckner via llvm-dev]

The conflict between COFF.h and windows.h is pretty unfortunate. I think the root cause of your problem is that COFF.h gets included transitively by MCSectionCOFF.h, but that header doesn't actually need COFF.h. I sunk COFF.h down into the .cpp files out of MCSectionCOFF.h, so now you shouldn't get these build errors at head.