BUG: Cannot build C++ project using MSVC 2019 and OpenBLAS

[larsoner]

On VS2019, trying to build using MSVC I get errors like the following:

[1/86] Building CXX object OpenMEEGMaths\CMakeFiles\OpenMEEGMaths.dir\src\vector.cpp.obj
FAILED: OpenMEEGMaths/CMakeFiles/OpenMEEGMaths.dir/src/vector.cpp.obj 
C:\PROGRA~2\MICROS~1\2019\ENTERP~1\VC\Tools\MSVC\1429~1.301\bin\Hostx64\x64\cl.exe  /nologo /TP -DH5_BUILT_AS_DYNAMIC_LIB -DHAVE_BLAS -DHAVE_LAPACK -DHAVE_SHARED_PTR_ARRAY_SUPPORT -DOpenMEEGMaths_EXPORTS -DUSE_OPENBLAS -I%SRC_DIR%\OpenMEEGMaths\include -I%SRC_DIR%\build_Release\OpenMEEGMaths -I%SRC_DIR%\build_Release -I%SRC_DIR%\OpenMEEGMaths\OpenMEEGMaths\src -external:I%PREFIX%\Library\include -external:W0 /wd4275 /wd4101 -openmp /MD /O2 /Ob2 /DNDEBUG -std:c++17 /showIncludes /FoOpenMEEGMaths\CMakeFiles\OpenMEEGMaths.dir\src\vector.cpp.obj /FdOpenMEEGMaths\CMakeFiles\OpenMEEGMaths.dir\ /FS -c %SRC_DIR%\OpenMEEGMaths\src\vector.cpp
%PREFIX%\Library\include\lapack.h(104): error C2143: syntax error: missing ',' before '*'
%PREFIX%\Library\include\lapack.h(106): error C2143: syntax error: missing ',' before '*'
... <hundreds of these>

You can see it on conda-forge here for example, where it uses the OpenBLAS libraries that they build:

https://dev.azure.com/conda-forge/feedstock-builds/_build/results?buildId=524975&view=logs&jobId=5be07ae1-d8ba-5406-47b6-8e3a3a12f825&j=5be07ae1-d8ba-5406-47b6-8e3a3a12f825&t=0bf03e01-0bec-5b85-5316-b1633322e895

And on GitHub actions here from earlier this week, same error -- this is using the OpenBLAS builds SciPy makes with mingw64, but I had the same problem when I tried previously just by downloading the 0.3.20 release binaries from GitHub:

Run cmake --build build  --config Release
Microsoft (R) Build Engine version 16.11.2+f32259642 for .NET Framework
Copyright (C) Microsoft Corporation. All rights reserved.
  Checking Build System
  Building Custom Rule D:/a/openmeeg/openmeeg/OpenMEEGMaths/CMakeLists.txt
  vector.cpp
C:\Program Files (x86)\Microsoft Visual Studio\2019\Enterprise\VC\Tools\MSVC\14.16.27023\include\xlocale(319): warning C4[53](https://github.com/openmeeg/openmeeg/runs/6975816876?check_suite_focus=true#step:16:54)0: C++ exception handler used, but unwind semantics are not enabled. Specify /EHsc [D:\a\openmeeg\openmeeg\build\OpenMEEGMaths\OpenMEEGMaths.vcxproj]
d:\a\openmeeg\openmeeg\openblas\64\include\lapack.h(104): error C2143: syntax error: missing ',' before '*' [D:\a\openmeeg\openmeeg\build\OpenMEEGMaths\OpenMEEGMaths.vcxproj]
d:\a\openmeeg\openmeeg\openblas\64\include\lapack.h(106): error C2143: syntax error: missing ',' before '*' [D:\a\openmeeg\openmeeg\build\OpenMEEGMaths\OpenMEEGMaths.vcxproj]
... <hundreds of these>

I am a bit mystified by this because these lines are protected by an ifdef that should take care of this I think:

https://github.com/xianyi/OpenBLAS/blob/9283c7c0b5a9ec7bbe3b6dfc1a019b29b3e112e5/lapack-netlib/LAPACKE/include/lapack.h#L71-L104

Anyone run into this before? I didn't see any mention of anything like this in the Visual Studio wiki docs, but maybe I just missed it. Perhaps it's a cmake+MSVC+CPP issue, and there is some cmake fix...? Not sure.

An identical build configuration using mingw64 doesn't have this problem... but I think for conda-forge I might need to build with MSVC. And in any case it would be nice if it worked...

[brada4]

Where did you get that lapack.h from?

[larsoner]

The include directory of the install step for OpenBLAS

[martin-frbg]

Same as what is in Reference-LAPACK actually. No idea why VS2019 does not like it, I'm fairly sure earlier versions did.

[larsoner]

Okay I opened a near-duplicate issue at Reference-LAPACK/lapack#683

[martin-frbg]

I guess you could try replacing the float _Complex in the definition of lapack_complex_float on line 39 with the Microsoft equivalent _Fcomplex (came across this when preparing the updated f2clapack that is now in the develop branch)
https://docs.microsoft.com/en-us/cpp/c-runtime-library/complex-math-support?view=msvc-170

[isuruf]

Not sure why we have this define at https://github.com/xianyi/OpenBLAS/blob/ad4598143bfbf77acd16f4ae884462edc69b496e/lapack-netlib/LAPACKE/include/lapack.h#L7
If that is removed and lapacke_config.h is included unconditionally, I think MSVC should be able to process the header just fine.

[martin-frbg]

File history suggests it has been this way ever since LAPACKE got integrated into the LAPACK package in 2011 - maybe the ifdef made sense when it was separate

[martin-frbg]

Also lapacke_config.h woud probably need a define LAPACK_COMPLEX_STRUCTURE dependent on (some variant spelling of) C_MSVC like there already is for older Android. (At least I see nothing defining this elsewhere, and without it we are back at float _Complex vs. _Fcomplex)

[martin-frbg]

@larsoner could you try @isuruf 's suggestion ?

[larsoner]

When I take the 0.3.18 headers and comment out lines 7 and 9 (#if and #endif) I still get a ton of errors like

  vector.cpp
c:\users\larsoner\python\openmeeg\openblas\64\include\lapacke_config.h(109): error C2146: syntax error: missing ';' bef
ore identifier 'lapack_make_complex_float' [C:\Users\larsoner\python\openmeeg\build\OpenMEEGMaths\OpenMEEGMaths.vcxproj
]
c:\users\larsoner\python\openmeeg\openblas\64\include\lapacke_config.h(109): error C4430: missing type specifier - int
assumed. Note: C++ does not support default-int [C:\Users\larsoner\python\openmeeg\build\OpenMEEGMaths\OpenMEEGMaths.vc
xproj]
c:\users\larsoner\python\openmeeg\openblas\64\include\lapacke_config.h(110): error C2371: '_Complex': redefinition; dif
ferent basic types [C:\Users\larsoner\python\openmeeg\build\OpenMEEGMaths\OpenMEEGMaths.vcxproj]

One other thing that might be relevant is this in the CMAKE config of the OpenMEEG project:

CMakeLists.txt:set(CMAKE_CXX_STANDARD 17)  # use c++17

so maybe this hasn't been noticed because nobody has compiled with MSVC using the c++17 standard...?

[brada4]

this is supposed to be complex or struct emulating it

[larsoner]

😱 I hope this issue doesn't turn out to be something like that where I missed something in OpenMEEG itself

I'll check next time I'm on my Windows boot...

[larsoner]

Okay I changed the lines @brada4 pointed out from their original form:

#if WIN32
    #define LAPACK_COMPLEX_CUSTOM
    #define lapack_complex_float float
    #define lapack_complex_double double
#endif

which show the problem on CIs in openmeeg/openmeeg#454, to a variant of what @martin-frbg originally suggested:

#if defined(_MSC_VER)
    #include <complex.h>
    #define LAPACK_COMPLEX_CUSTOM
    #define lapack_complex_float _Fcomplex
    #define lapack_complex_double _Dcomplex
#endif

And things compile fine with openmeeg/openmeeg@6eb29e8 locally with MSVC 2017 at least and tests pass, though I still need to convince MSVC 2019 in CIs to accept it! 🚀

I'll close this as fixed, and I've updated the MSVC instruction page to mention this: https://github.com/xianyi/OpenBLAS/wiki/How-to-use-OpenBLAS-in-Microsoft-Visual-Studio#visual-studio-2017-c2017-standard