How to build mscordaccore_amd64_arm64_*?

[Arjunarus]

We build windows arm64 runtime from sources on win x86_64 host using build.cmd -arch arm64 <...> and want to analyze arm64 dumps in windbg. To make this possible windbg downloads corresponding mscordaccore.dll from symbol server.

Our arm64 build has only mscordaccore_arm64_arm64_.dll which is for using on arm64 host, but we need to debug on win x86_64 machine, so if I understad correctly, we need mscordaccore_amd64_arm64_.dll.

So the question: is it possible to build such hybrid mscordaccore_amd64_arm64 from 8.0.19 sources version and how to do this? I tried to setup CLR_CMAKE_HOST_ARCH=x64, but it seems do not work.

[Martik2002]

Yes, it is possible to build the hybrid DAC (mscordaccore_amd64_arm64.dll) from the .NET 8.0.19 sources, but you need to explicitly build the cross-architecture DAC. By default, the build system only produces mscordaccore_arm64_arm64.dll, which is for debugging on an ARM64 host.

To generate the AMD64-to-ARM64 DAC (for analyzing ARM64 dumps on an x64 WinDbg), you should build with:

build.cmd clr.dac -hostarch x64 -arch arm64

This tells the runtime build system that the host (debugger) architecture is x64 while the target architecture is ARM64. After the build completes, you should find mscordaccore_amd64_arm64_[version].dll under the artifacts\bin\coreclr\Windows_NT.x64.[Configuration]\ directory.

If you still see only arm64_arm64, make sure cross-components are enabled. You can also try:

build.cmd clr.runtime -hostarch x64 -arch arm64

That will build the runtime plus DAC for the cross configuration.

In short: yes, you can build it yourself, but you need to select the cross DAC subset and specify both hostarch and arch correctly.

[Arjunarus]

Sorry, but I know how to use AI. This answer from AI is not relevant: there is no such subset as clr.dac and there is no argument -hostarch. I already asked from AI and it said similar garbage things.
I'd like to get answer from people who know how the dotnet building process works.
I already found CLR_CROSS_COMPONENTS_BUILD cmake variable and try to use it, but no success yet.

[Arjunarus]

I found a proper command:
.\src\coreclr\build-runtime.cmd -arm64 -hostarch x64 -os windows -component crosscomponents -cmakeargs "-DCLR_CROSS_COMPONENTS_BUILD=1"
and I also find that it is already run during the standard build, I just needed to find corresponding artifacts in artifacts folder:
artifacts\bin\coreclr\windows.arm64.Release\x64\sharedFramework\