The AOT compiler doesn't support a MONO_PATH with a colon

[rolfbjarne]

Description

We use MONO_PATH to point to the directory where all the assemblies are for the AOT compiler.

Unfortunately, the Mono allows for multiple paths in MONO_PATH, splitting them by colon:

runtime/src/mono/mono/metadata/assembly.c

Line 137 in 34b6db9

split = g_strsplit (path, G_SEARCHPATH_SEPARATOR_S, 1000);

this means that we can't use the AOT compiler for a path with a colon in it.

Now why would that ever happen?

It happens when building remotely from Windows, and [Intermediate]OutputPath is set to a full (Windows) path. In that case, all the assemblies end up in a directory with a colon in it on the Mac: dotnet/macios#14904.

This wasn't very common, because [Intermediate]OutputPath used to be relative paths. However, with the new artifacts output path in .NET 8, [Intermediate]OutputPath are both absolute paths.

Reproduction Steps

mkdir colonexample && cd colonexample
dotnet new ios
dotnet build /p:RuntimeIdentifier=ios-arm64 /p:IntermediateOutputPath=$PWD/l:i:b/ /bl
[...]
/usr/local/share/dotnet/packs/Microsoft.iOS.Sdk/16.4.7090/targets/Xamarin.Shared.Sdk.targets(1045,3): error : Failed to AOT compile System.Runtime.dll, the AOT compiler exited with code 134 [/Users/rolf/test/dotnet/colonexample/colonexample.csproj]
/usr/local/share/dotnet/packs/Microsoft.iOS.Sdk/16.4.7090/targets/Xamarin.Shared.Sdk.targets(1045,3): error : Failed to AOT compile System.Runtime.InteropServices.dll, the AOT compiler exited with code 134 [/Users/rolf/test/dotnet/colonexample/colonexample.csproj]
/usr/local/share/dotnet/packs/Microsoft.iOS.Sdk/16.4.7090/targets/Xamarin.Shared.Sdk.targets(1045,3): error : Failed to AOT compile colonexample.dll, the AOT compiler exited with code 134 [/Users/rolf/test/dotnet/colonexample/colonexample.csproj]
[...]

Expected behavior

No crash.

Actual behavior

Crash.

Binlog:
msbuild.binlog.zip

Regression?

No, but importance has increased due to unrelated changes making the scenario more frequent.

Known Workarounds

No response

Configuration

$ $ dotnet --info
.NET SDK:
 Version:   7.0.306
 Commit:    f500069cb7

Runtime Environment:
 OS Name:     Mac OS X
 OS Version:  13.5
 OS Platform: Darwin
 RID:         osx.13-arm64
 Base Path:   /usr/local/share/dotnet/sdk/7.0.306/

Host:
  Version:      7.0.9
  Architecture: arm64
  Commit:       8e9a17b221

.NET SDKs installed:
  7.0.306 [/usr/local/share/dotnet/sdk]

.NET runtimes installed:
  Microsoft.AspNetCore.App 7.0.9 [/usr/local/share/dotnet/shared/Microsoft.AspNetCore.App]
  Microsoft.NETCore.App 7.0.9 [/usr/local/share/dotnet/shared/Microsoft.NETCore.App]

Other architectures found:
  None

Environment variables:
  Not set

global.json file:
  Not found

Learn more:
  https://aka.ms/dotnet/info

Download .NET:
  https://aka.ms/dotnet/download

Other information

No response

[vargaz]

Colon is the unix path separator. Maybe we can support a backslash escaped colon.

[kotlarmilos]

Colon is the unix path separator. Maybe we can support a backslash escaped colon.

Would that require changing Xamarin build to escape the paths?

It happens when building remotely from Windows

@rolfbjarne Does that mean targeting Windows from Unix platforms (or other way)?

As Zoltan said, ':' is the unix path separator, while ';' is the windows path separator. It is already implemented in that way, but may require changing the HOST_WIN32 to TARGET_WIN32 in:

runtime/src/mono/CMakeLists.txt

Lines 805 to 831 in 8323e58

	if(HOST_WIN32)
	set(EGLIB_GNUC_PRETTY "__FUNCTION__")
	set(EGLIB_BREAKPOINT "__debugbreak()")
	set(EGLIB_PATHSEP "\\\\")
	set(EGLIB_SEARCHSEP ";")
	set(EGLIB_OS "WIN32")
	set(EGLIB_PIDTYPE "void *")
	if(HOST_AMD64 OR HOST_ARM64)
	set(EGLIB_GSIZE_FORMAT "\"Iu\"")
	else()
	set(EGLIB_GSIZE_FORMAT "\"u\"")
	endif()
	else()
	set(EGLIB_BREAKPOINT "G_STMT_START { raise(SIGTRAP); } G_STMT_END")
	if(GCC)
	set(EGLIB_GNUC_UNUSED "__attribute__((__unused__))")
	set(EGLIB_GNUC_NORETURN "__attribute__((__noreturn__))")
	if(HOST_AMD64 OR HOST_X86)
	set(EGLIB_BREAKPOINT "G_STMT_START { __asm__(\"int \$03\"); } G_STMT_END")
	endif()
	endif()
	set(EGLIB_PATHSEP "/")
	set(EGLIB_SEARCHSEP ":")
	set(EGLIB_OS "UNIX")
	set(EGLIB_PIDTYPE "int")
	set(EGLIB_GSIZE_FORMAT "\"zu\"")
	endif()

As a quick fix, we may implement escaping the ':\' for windows targets only.

[rolfbjarne]

Colon is the unix path separator. Maybe we can support a backslash escaped colon.

Would that require changing Xamarin build to escape the paths?

Yes.

It happens when building remotely from Windows

@rolfbjarne Does that mean targeting Windows from Unix platforms (or other way)?

It means building an iOS project on a (remote) Mac using Windows.

As a quick fix, we may implement escaping the ':' for windows targets only.

This isn't happening when executing on Windows, it's when executing on Mac, so doing something for Windows only won't help us :)

That said, I believe that adding an escaping mechanism would be the solution (while colon is the unix path separator, it's also a legal character in a file name).

[vargaz]

Another option would be adding a --path command line argument which would append to the path.

[SamMonoRT]

PR to fix this is #90544