[Bug]: MSVC throws internal compiler error when using `quantity_point<deg_C>`

[Wyverex42]

Bug Description

Observed on both MSVC 19.44.35224 and 19.50.35728.

When initializing a quantity_point<deg_C>, MSVC throws an internal error:

C:\PROGRA1\MICROS4\18\PROFES1\VC\Tools\MSVC\14501.357\bin\Hostx64\x64\cl.exe /nologo /TP -DFMT_SHARED -DMP_UNITS_API_CONTRACTS=2 -DMP_UNITS_API_NATURAL_UNITS=1 -DMP_UNITS_API_NO_CRTP=0 -DMP_UNITS_API_STD_FORMAT=0 -DMP_UNITS_API_THROWING_CONSTRAINTS=0 -DMP_UNITS_HOSTED=1 -D_HAS_EXCEPTIONS=0 -D_MBCS -ID:\dev\foundation-sdk\libs\log\include -ID:\dev\foundation-sdk\libs\core\include -external:ID:\dev\foundation-sdk\build\dev\vcpkg_installed\x64-windows\include -external:W0 /DWIN32 /D_WINDOWS /Ob0 /Od -std:c++20 -MDd -RTC1 -Zi /W4 /permissive- /w14242 /w14254 /w14263 /w14265 /w14287 /w14296 /w14311 /w14545 /w14546 /w14547 /w14549 /w14555 /w14619 /w14640 /w14826 /w14905 /w14906 /w14928 /WX /EHs-c- /utf-8 /showIncludes @examples\foundation-example-app\CMakeFiles\foundation-example-app.dir\main.cpp.obj.modmap /Foexamples\foundation-example-app\CMakeFiles\foundation-example-app.dir\main.cpp.obj /Fdexamples\foundation-example-app\CMakeFiles\foundation-example-app.dir\ /FS -c D:\dev\foundation-sdk\examples\foundation-example-app\main.cpp
D:\dev\foundation-sdk\build\dev\vcpkg_installed\x64-windows\include\mp-units/framework/reference.h(54): fatal error C1001: Internal compiler error.

Is there any workaround for this? Unfortunately this looks like stopping mp-units dead in its tracks for our use case based on Unreal on Windows.

Steps to Reproduce

// Minimal reproducible example
#include <mp-units/systems/si.h>

int main()
{
	using namespace mp_units::si::unit_symbols;
	mp_units::quantity_point<deg_C> temp = mp_units::point<deg_C>(100);
	return 0;
}

🚀 Compiler Explorer Link (Recommended)

No response

Compiler

MSVC 194

C++ Standard

C++20

mp-units Version

2.5.0 via vcpkg

Build Configuration

• Using Conan
• Using CMake directly
• Header-only mode
• C++ modules enabled
• Freestanding mode
• Debug build
• Release build

Additional Context

No response

Checklist

• I have read the documentation and checked existing issues

[mpusz]

Hi @Wyverex42!

Thanks a lot for trying the library and reporting. Unfortunately, I can't do much beyond asking the MSVC team to help again.

You are not alone. Other companies like Garmin are also waiting for the MSVC team to fix their compiler so they can start using it in production.

I am really sorry you are having those issues, but even the MSVC developers told me there are no easy workarounds for those crashes. We have to submit MSVC bugs, escalate them, and hope the compiler improves soon.

[Radnyx]

The compiler bug is fixed in v14.51 of the toolset (aka MSVC 19.51.36014). This version is currently a preview, so you'll need to opt-in in the Visual Studio installer: https://devblogs.microsoft.com/cppblog/microsoft-c-msvc-build-tools-v14-51-preview-released-how-to-opt-in/