Any plans for an ARM64-compatible release

[andyraf]

Are there any plans to support an ARM64-compatible release of Git for Windows?

[PhilipOakley]

My ignorance here, but is Windows on ARM64?

This maybe an 'upstream' question to see if the new Azure CI capability could build and test for ARM (and maybe the Rasp pi? he says with ulterior motives...)

[dscho]

Are there any plans to support an ARM64-compatible release of Git for Windows?

I looked into it, and the main issue is the lack of an ARM64 version of MSYS2. There does seem to exist an ARM64 version (at least a preliminary one) of Cygwin (on which MSYS2 is based), so there is hope.

However, I would like to encourage everybody who is interested in ARM64 support to chip in some work, as there is plenty to do before we will have a working Git for Windows on ARM64. Like, highly encourage.

I talk about MSYS2 because we need this for the parts of Git that are still implemented as Unix shell and Perl scripts (git bisect and git submodule are probably the two most prominent ones).

In the short run, if you should try to build Git for Windows yourself, in Visual Studio, by cloning this repository and checking out vs/master. Last time I checked, this failed to build the prerequisites, apparently vcpkg did not support building OpenSSL for ARM64 back then (this might have changed, see https://github.com/microsoft/vcpkg/releases for more details).

[ssimontis]

It's my understanding that you can only natively build ARM64 apps on Windows if they are based off of UWP. Otherwise, there is an x86 emulator for running Win32 applications, and Microsoft announced in November that they were working on an x64 emulator for Windows applications. I think we would need to wait until Microsoft makes x64 emulation generally available to approach this. If there's any preliminary work I can do in the mean time that would help out, please feel free to let me know and I will be happy to see what I can do.

[manbearian]

@dscho I'm interested in helping with bringing Git for Windows to ARM64. Locally i was able to get the vckpg dependencies built for ARM64 with only a tiny bit of hacking. The result of my efforts is a an ARM64 git.exe binary that at least dumps the help message successfully on my ARM laptop (i haven't tried anything else yet). Would you like to chat either here or offline about what you see as the full list of work that might be required beyond this?

ian Bearman
Principal Software Engineering Manager
Microsoft Visual C++ Team: Optimization & Code Generation
/* Making your code faster, smaller, smarter! */

[dscho]

That sounds amazing! Let's chat here, okay?

One of the biggest obstacles to getting Git to work on ARM is the lack of a Bash. But many things already work without a Bash...

So we could aim first for building a slightly incomplete Git for Windows (ARM64 edition) using the Visual C build.

What was that hackery you needed? Patches to vcpkg?

[manbearian]

I can create a PR for my changes, but i'm not sure the process for this. The changes are all in the 'git' source tree. Is there doc/contributors guide that covers this?

In the meantime, here's an outline of what i did based on SDK-64:

• project/sln changes (through perl script)
  • upgrade project to more recent VS (required to get ARM64 compilers, i picked latest, v142).
  • add ARM64 build configurations to projects/solution
  • added an item to the vcxprojs for VCPKGArch to be set correctly for ARM64
• source changes
  • update compat/bswap.h
• vcpkg changes
  • update compat/vcbuild/vcpg_install.bat to install both x64 and ARM64 packages
  • manually run the vcpkg_install script to install ARM64 packages

After these changes, building the git.sln for ARM64 "just works". I copied over to my ARM64 device and i have some very basic functionality working (i.e. the logo and help message). I dropped the binary into a folder layout matching an installed version and things got a bit better, but authentication for a fetch didn't work (missing DLLs i believe) and git checkout doesn't work if there are any new files (i didn't look further into this last week).

Is there a top-down view i can get of dependencies? That might be better than stabbing tin the dark looking for missing pieces. Additionally, i couldn't find documentation on building the installer, which i thought might give me a clue as to what binaries i need to look for.

[rimrul]

The documentation for building an installer is at https://github.com/git-for-windows/git/wiki/Making-an-installer

[manbearian]

Btw, i've tried to push my local changes to the git repo, but its not working for me...

C:\git-sdk-64\usr\src\git>"C:\Program Files\Git\cmd\git.exe" push --set-upstream origin initialArm64 remote: Permission to git-for-windows/git.git denied to manbearian. fatal: unable to access 'https://github.com/git-for-windows/git/': The requested URL returned error: 403
Ideas?

[rimrul]

You don't have push access to git-for-windows/git (very few people do). Click "Fork" near the top to create a copy on your github account, push there, then create a pull request.

[manbearian]

I'm making steady progress by mixing x86 binaries (from x86 install of Git for Windows) and the ARM64 binaries i built. I'm blocked on a few things right now and any help on these is appreciated:

1. trying to make progress on clone: i can now clone from a repo on github (e.g. my copy of git sources), however i cannot clone something in Azure DevOps. Likely related to authentication, but i'm seeing this message:

Cloning into 'c:\msvc1'...
fatal: Unsupported SSL backend 'openssl'. Supported SSL backends:
        schannel

i'm not sure where to start to investigate this, so pointers to what the authentication process or where its located in source at lest might give me a push in the right direction.

2. I successfully built a setup (thank for the instruction), but its not quite what i need for a few reasons: first the setup doesn't seem to contain the ARM64 git.exe that i built locally, not sure from where/what it grabbed its binaries. second, the setup didn't ask the usual Qs that setup asks, not sure if that is something i did wrong or not.

3. finally, related to setup: one path, which i think is a good one, in the direction toward getting something viable on ARM64 Windows is to get a setup that mixes 32-bit x86 and ARM64. (e.g. mingw32). This is because the emulator on ARM64 Windows only supports 32-bit x86 binaries.

Please let me know your thoughts on these topics.

thanks,
ian

[manbearian]

Spending time debugging fatal: Unsupported SSL backend 'openssl' has lead me to the conclusion that the libcurl i have is built without OPENSSL, (i see -DCMAKE_USE_OPENSSL=OFF in my build log) but that feature seems to be enabled in the version that i have installed. When i run git config --system -l i see http.sslbackend=openssl, and this setting seems to be sending git-remote-http.exe down the path that won't work.

The libcurl dependency is a vcpkg dependency... so i didn't run any configuration on it: is there possibly something strange here? Is this is a scenario that is not tested in VS build scenario?

Additional help is appreciated.