Can't build with NativeAOT on Windows

[rolfbjarne]

Apple platform

iOS

Framework version

net9.0-*

Affected platform version

.NET 9

Description

Publishing a project on Windows with PublishAot=true yields:

d:\AzDO_work\8\s\xamarin-macios\packages\microsoft.dotnet.ilcompiler\9.0.0\build\Microsoft.NETCore.Native.Unix.targets(115): error: 'xcrun' not found in PATH. Make sure 'xcrun' is available in PATH.

Steps to Reproduce

dotnet new ios
dotnet build /p:_IsPublishing=true /p:PublishAot=true /p:RuntimeIdentifier=ios-arm64 /p:ServerAddress=... /p:ServerUser=... /p:ServerPassword=...

There's a test case in this PR: #21800

Build logs

The binlog contains secrets, so I can provide it upon request (or re-create one).

The target that fails:

Target Name=SetupOSSpecificProps Project=d:\AzDO\_work\8\s\xamarin-macios\tests\dotnet\MySimpleApp\iOS\MySimpleApp.csproj
    UseSystemZlib = true
    FullRuntimeName = libRuntime.WorkstationGC
    CrossCompileRid = 
    CrossCompileRid = ios-arm64
    CrossCompileArch = 
    CrossCompileArch = arm64
    CrossCompileAbi = gnu
    Task "Exec" skipped, due to false condition; ('$(CrossCompileArch)' != '' and '$(SysRoot)' != '') was evaluated as ('arm64' != '' and '' != '').
    TargetTriple = 
    TargetTriple = arm64-linux-gnu
    IlcRPath = @executable_path
    EventPipeName = libeventpipe-disabled
    LinkStandardCPlusPlusLibrary = true
    VxSortSupportName = libRuntime.VxsortEnabled
    StandaloneGCSupportName = libstandalonegc-disabled
    AppleMinOSVersion = 12.2
    _AppleSdkName = iphoneos
    _AppleTripleOS = ios
    _AppleTripleAbi = macho
    TargetTriple = arm64-apple-ios12.2-macho
    Task "Error" skipped, due to false condition; ('$(_IsiOSLikePlatform)' == 'true' and ('$(_AppleSdkName)' == '' or '$(CrossCompileArch)' == '' or '$(_AppleTripleOS)' == ''  or '$(AppleMinOSVersion)' == '' or '$(_AppleTripleAbi)' == '')) was evaluated as ('true' == 'true' and ('iphoneos' == '' or 'arm64' == '' or 'ios' == ''  or '12.2' == '' or 'macho' == '')).
    Xcrun = xcrun
    _WhereXcrun = 0
    Exec
        Assembly = D:\AzDO\_work\8\s\xamarin-macios\tests\dotnet\Windows\bin\dotnet\packs\Microsoft.iOS.Sdk.net9.0_18.1\18.1.9220-ci.pr.gh21800\tools\msbuild\Xamarin.MacDev.Tasks.dll
        Parameters
            Command = command -v "xcrun"
            IgnoreExitCode = True
            StandardOutputImportance = Low
        CommandLineArguments = command -v "xcrun"
        'command' is not recognized as an internal or external command,
        operable program or batch file.
        The command "command -v "xcrun"" exited with code 9009.
        OutputProperties
            _WhereXcrun = 9009
    Error
        Assembly = D:\AzDO\_work\8\s\xamarin-macios\tests\dotnet\Windows\bin\dotnet\sdk\9.0.102\Microsoft.Build.Tasks.Core.dll
        Parameters
            Text = 'xcrun' not found in PATH. Make sure 'xcrun' is available in PATH.
        Errors
            d:\AzDO\_work\8\s\xamarin-macios\packages\microsoft.dotnet.ilcompiler\9.0.0\build\Microsoft.NETCore.Native.Unix.targets(115,5): 'xcrun' not found in PATH. Make sure 'xcrun' is available in PATH. [d:\AzDO\_work\8\s\xamarin-macios\tests\dotnet\MySimpleApp\iOS\MySimpleApp.csproj]

[rolfbjarne]

This is where it fails, which obviously won't work on Windows:

https://github.com/dotnet/runtime/blob/7927a192be28c8562a54becdbe0a665837022eaa/src/coreclr/nativeaot/BuildIntegration/Microsoft.NETCore.Native.Unix.targets#L116-L118

The logic seems to want to verify that xcrun is in PATH, and then goes on to use xcrun to compute SysRoot:

https://github.com/dotnet/runtime/blob/7927a192be28c8562a54becdbe0a665837022eaa/src/coreclr/nativeaot/BuildIntegration/Microsoft.NETCore.Native.Unix.targets#L122-L124

which is then used to add -isysroot ... to LinkerArg:

https://github.com/dotnet/runtime/blob/7927a192be28c8562a54becdbe0a665837022eaa/src/coreclr/nativeaot/BuildIntegration/Microsoft.NETCore.Native.Unix.targets#L232

which is never used again...

There seems to be few possible solutions here:

• Figure out a way to tell the NativeAOT build logic to not bother computing LinkerArg, because it's not going to be used.
• Support setting SysRoot before the SetupOSSpecificProps target, so that it won't be necessary to run xcrun to detect it (and then also not detect if xcrun is in PATH either).

CC @ivanpovazan is this something you can help with?

[ivanpovazan]

Yes, definitely! :)

Was this found internally or by a customer?

Sounds like we will have to service the fix.

[rolfbjarne]

Was this found internally or by a customer?

By a customer: #21795 (comment)

[ivanpovazan]

@rolfbjarne regarding:

Support setting SysRoot before the SetupOSSpecificProps target, so that it won't be necessary to run xcrun to detect it (and then also not detect if xcrun is in PATH either).

How would SysRoot be resolved in the Xamarin SDK?

[rolfbjarne]

@rolfbjarne regarding:

Support setting SysRoot before the SetupOSSpecificProps target, so that it won't be necessary to run xcrun to detect it (and then also not detect if xcrun is in PATH either).

How would SysRoot be resolved in the Xamarin SDK?

We have our own targets that compute it.

[ivanpovazan]

Just an update:

• I looked into working around the SetupOSSpecificProps logic if _SdkRoot and/or SysRoot are specified and that got me further.
• The next problem we hit, is the fact that we try to cross compile with ILC from windows to iOS which is not supported nor it should happen as the AOT compiler should run on the paired Mac

Looking into it.

[rolfbjarne]

• The next problem we hit, is the fact that we try to cross compile with ILC from windows to iOS which is not supported nor it should happen as the AOT compiler should run on the paired Mac

The way we've solved this in the past is to create a task of our own that subclasses the original task, and which provides the necessary remoting.

See our ILLink task for example:

https://github.com/dotnet/macios/blob/main/msbuild/Xamarin.MacDev.Tasks/Tasks/ILLink.cs

macios/msbuild/Xamarin.iOS.Tasks.Windows/Xamarin.iOS.Common.After.targets

Lines 342 to 344 in bd02649

	<!-- Overrides Core SDK target to remote the ILLink execution -->
	<!-- https://github.com/dotnet/sdk/blob/cdf57465e1cba9e44b5c9a76a403d41b1b8f178c/src/Tasks/Microsoft.NET.Build.Tasks/targets/Microsoft.NET.ILLink.targets#L76-L132 -->
	<Target Name="_RunILLink"