CMake + Intel 19 + VS 2019 -> Error while determining compiler.

Error: error : Element <LanguageStandard> has an invalid value of "Default".
Relevant Intel issue: https://software.intel.com/en-us/forums/intel-c-compiler/topic/811512

Possible Solution: Add <LanguageStandard>stdcpp14</LanguageStandard> in <ClCompile> to VS-10.vcxproj.in in share/cmake-3.15/Modules/CompilerId

Probably an Intel integration issue and not a CMake issue? Just documenting here if questions arise.

changed title from CMake + Intel 19 + VS 2019 -> Error while determining compiler. to CMake + Intel 19u4 + VS 2019 -> Error while determining compiler.

Thanks for reporting this.

For reference, I also see it reported here: https://software.intel.com/en-us/forums/intel-c-compiler/topic/820243

added triage:env-regression label

changed milestone to %3.16.0

assigned to @brad.king

changed title from CMake + Intel 19u4 + VS 2019 -> Error while determining compiler. to CMake + Intel 19 + VS 2019 -> Error while determining compiler.

added comp:intel gen:vs labels

Comparing the VS 2017 and VS 2019 versions of the file mentioned in this post:

• C:\...\2017\Professional\Common7\IDE\VC\VCTargets\Microsoft.Cl.Common.props
• C:\...\2019\Professional\MSBuild\Microsoft\VC\v160\Microsoft.Cl.Common.props

There are only a few differences, but one of them is:

+      <LanguageStandard                 Condition="'%(ClCompile.LanguageStandard)'              == ''">Default</LanguageStandard>

VS 2019 adds this new Default value for LanguageStandard and the Intel Compiler Visual Studio Integration cannot handle it. This can break projects created without CMake too. Ideally Intel should fix their integration logic to handle this setting.

Without a fix from Intel we may need to consider workarounds here.

The VS 2017 file

C:\Program Files (x86)\Microsoft Visual Studio\2017\Professional\Common7\IDE\VC\VCTargets\1033\cl.xml

has an enumeration of allowed LanguageStandard values and the corresponding compiler flags. It maps stdcpp14 to -std:c++14, stdcpp17, to -std:c++17, and stdcpplatest to -std:c++latest.

The Intel Compiler 2019 VS 2017 integration file:

C:\Program Files (x86)\Microsoft Visual Studio\2017\Professional\Common7\IDE\VC\VCTargets\Platforms\x64\PlatformToolsets\Intel C++ Compiler 19.0\1033\icl.xml

has the same enumeration with the same entries.

The VS 2019 file

C:\Program Files (x86)\Microsoft Visual Studio\2019\Professional\MSBuild\Microsoft\VC\v160\1033\cl.xml

has the same enumeration as the 2017 version but also adds an additional value called Default that maps to nothing ("").

The Intel Compiler 2019 VS 2019 integration file:

C:\Program Files (x86)\Microsoft Visual Studio\2019\Professional\MSBuild\Microsoft\VC\v160\Platforms\x64\PlatformToolsets\Intel C++ Compiler 19.0\1033\icl.xml

is missing the entry for Default. Intel should modify the file to add the value:

+    <EnumValue Name="Default" Switch="" DisplayName="Default">
+    </EnumValue>

to fix this problem.

Hacking the icl.xml file to add the <EnumValue Name="Default" ... entry to the enumeration does not fix this for me. I'm not familiar enough with MSBuild to know why.

Intel needs to fix this.

Without the proper Default value there is no way to use the Intel Compiler 2019 with no -std: flag through its Visual Studio integration.

If we work around this by setting LanguageStandard to stdcpp14 then VS will always add the -std:c++14 flag. This is the default mode:

>type lang.cpp
_MSVC_LANG

>icl -E lang.cpp
#line 1 "lang.cpp"
201402L

>icl -std:c++14 -E lang.cpp
#line 1 "lang.cpp"
201402L

However, there may be other effects on extensions and such.

Setting LanguageStandard to stdcpp14 as a work around is problematic in a .vcxproj file for C programs. It results in -std:c++14 being passed on the command line even for a .c source file. Normally that doesn't make much difference but if one is also adding a flag like -Qstd=c11 to the AdditionalOptions to change the C standard level, then the compiler warns:

icl: : warning #10428: '/Qstd:<arg>' conflicts with '/std:<arg>'; using '/Qstd:<arg>'

mentioned in merge request !3808 (closed)

See !3808 (closed) for an attempt at working around this.

removed milestone

unassigned @brad.king

So I updated to 19 Update 5 which was released today and it seems to be fixed there

@Neumann-A thanks! I updated to that and indeed it is fixed.

The file

C:\Program Files (x86)\Microsoft Visual Studio\2019\Professional\MSBuild\Microsoft\VC\v160\Platforms\x64\PlatformToolsets\Intel C++ Compiler 19.0\1033\icl.xml

now has the Default entry for LanguageStandard, and the problem does not occur.

closed