gcc fails to arch-cross-compile on GNU/Linux in NativeAOT .NET 7

[WhiteBlackGoose]

Description

Getting an error

gcc : error : unrecognized command-line option '--target=aarch64-linux-gnu'

When trying to compile my app for ARM64 while being on x86 64bit laptop

Reproduction Steps

1. dotnet new console -n frog && cd frog
2. dotnet publish -p:PublishAot=true -p:SelfContained=true -r linux-arm64

Expected behavior

Compiles

Actual behavior

Doesn't compile:

$ dotnet publish -p:PublishAot=true -p:SelfContained=true -r linux-arm64
MSBuild version 17.4.0+18d5aef85 for .NET
  Determining projects to restore...
  All projects are up-to-date for restore.
  frog -> /home/goose/sandbox-1668781319/frog/bin/Debug/net7.0/linux-arm64/frog.dll
  Generating native code
gcc : error : unrecognized command-line option '--target=aarch64-linux-gnu' [/home/goose/sandbox-1668781319/frog/frog.csproj]
/home/goose/programs/dotnet-folder/sdk/7.0.100/Sdks/Microsoft.DotNet.ILCompiler/build/Microsoft.NETCore.Native.targets(346,5): error MSB3073: The command ""gcc" "obj/Debug/net7.0/linux-arm64/native/frog.o" -o "bin/Debug/net7.0/linux-arm64/native/frog" /home/goose/.nuget/packages/runtime.linux-arm64.microsoft.dotnet.ilcompiler/7.0.0/sdk/libbootstrapper.a /home/goose/.nuget/packages/runtime.linux-arm64.microsoft.dotnet.ilcompiler/7.0.0/sdk/libRuntime.WorkstationGC.a /home/goose/.nuget/packages/runtime.linux-arm64.microsoft.dotnet.ilcompiler/7.0.0/framework/libSystem.Native.a /home/goose/.nuget/packages/runtime.linux-arm64.microsoft.dotnet.ilcompiler/7.0.0/framework/libSystem.Globalization.Native.a /home/goose/.nuget/packages/runtime.linux-arm64.microsoft.dotnet.ilcompiler/7.0.0/framework/libSystem.IO.Compression.Native.a /home/goose/.nuget/packages/runtime.linux-arm64.microsoft.dotnet.ilcompiler/7.0.0/framework/libSystem.Net.Security.Native.a /home/goose/.nuget/packages/runtime.linux-arm64.microsoft.dotnet.ilcompiler/7.0.0/framework/libSystem.Security.Cryptography.Native.OpenSsl.a --target=aarch64-linux-gnu -g -Wl,-rpath,'$ORIGIN' -Wl,--build-id=sha1 -Wl,--as-needed -pthread -lstdc++ -ldl -lm -lz -lrt -pie -Wl,-z,relro -Wl,-z,now -Wl,--discard-all -Wl,--gc-sections" exited with code 1. [/home/goose/sandbox-1668781319/frog/frog.csproj]

Regression?

No response

Known Workarounds

No response

Configuration

1. 7.0.100
2. debian 12 sid bookworm
3. x86 64-bit
4. gcc (Debian 12.2.0-9) 12.2.0
5. aarch64-linux-gnu-gcc (Debian 12.2.0-9) 12.2.0
6. No clang installed

Other information

No response

Tagging subscribers to this area: @agocke, @MichalStrehovsky, @jkotas
See info in area-owners.md if you want to be subscribed.

Issue Details

---

Description

Getting an error

gcc : error : unrecognized command-line option '--target=aarch64-linux-gnu'

When trying to compile my app for ARM64 while being on x86 64bit laptop

Reproduction Steps

1. dotnet new console -n frog && cd frog
2. dotnet publish -p:PublishAot=true -p:SelfContained=true -r linux-arm64

Expected behavior

Compiles

Actual behavior

Doesn't compile:

$ dotnet publish -p:PublishAot=true -p:SelfContained=true -r linux-arm64
MSBuild version 17.4.0+18d5aef85 for .NET
  Determining projects to restore...
  All projects are up-to-date for restore.
  frog -> /home/goose/sandbox-1668781319/frog/bin/Debug/net7.0/linux-arm64/frog.dll
  Generating native code
gcc : error : unrecognized command-line option '--target=aarch64-linux-gnu' [/home/goose/sandbox-1668781319/frog/frog.csproj]
/home/goose/programs/dotnet-folder/sdk/7.0.100/Sdks/Microsoft.DotNet.ILCompiler/build/Microsoft.NETCore.Native.targets(346,5): error MSB3073: The command ""gcc" "obj/Debug/net7.0/linux-arm64/native/frog.o" -o "bin/Debug/net7.0/linux-arm64/native/frog" /home/goose/.nuget/packages/runtime.linux-arm64.microsoft.dotnet.ilcompiler/7.0.0/sdk/libbootstrapper.a /home/goose/.nuget/packages/runtime.linux-arm64.microsoft.dotnet.ilcompiler/7.0.0/sdk/libRuntime.WorkstationGC.a /home/goose/.nuget/packages/runtime.linux-arm64.microsoft.dotnet.ilcompiler/7.0.0/framework/libSystem.Native.a /home/goose/.nuget/packages/runtime.linux-arm64.microsoft.dotnet.ilcompiler/7.0.0/framework/libSystem.Globalization.Native.a /home/goose/.nuget/packages/runtime.linux-arm64.microsoft.dotnet.ilcompiler/7.0.0/framework/libSystem.IO.Compression.Native.a /home/goose/.nuget/packages/runtime.linux-arm64.microsoft.dotnet.ilcompiler/7.0.0/framework/libSystem.Net.Security.Native.a /home/goose/.nuget/packages/runtime.linux-arm64.microsoft.dotnet.ilcompiler/7.0.0/framework/libSystem.Security.Cryptography.Native.OpenSsl.a --target=aarch64-linux-gnu -g -Wl,-rpath,'$ORIGIN' -Wl,--build-id=sha1 -Wl,--as-needed -pthread -lstdc++ -ldl -lm -lz -lrt -pie -Wl,-z,relro -Wl,-z,now -Wl,--discard-all -Wl,--gc-sections" exited with code 1. [/home/goose/sandbox-1668781319/frog/frog.csproj]

Regression?

No response

Known Workarounds

No response

Configuration

1. 7.0.100
2. debian 12 sid bookworm
3. x86 64-bit
4. gcc (Debian 12.2.0-9) 12.2.0
5. aarch64-linux-gnu-gcc (Debian 12.2.0-9) 12.2.0
6. No clang installed

Other information

No response

Author:	WhiteBlackGoose
Assignees:	-
Labels:	untriaged, area-NativeAOT-coreclr
Milestone:	-

[am11]

We haven't tested cross-compilation with gcc, so this is unsupported. We can add support for it. However, there are few things to consider:

• clang has multi targets support (and hence -target/--target options are supported), but gcc only has one main target for which it was built for. We don't check the compiler flavor when setting this option (which is a bug).
• user will need to install target specific gcc toolchain to be able to use gcc for cross compilation.

You can install clang (or use a docker image) for the cross-compilation in the meantime.

[jkotas]

Cross-compilation instructions are at https://github.com/dotnet/runtime/blob/main/src/coreclr/nativeaot/docs/compiling.md#cross-architecture-compilation . Cross-compilation on Linux requires rootfs and target architecture native toolchain to be present.

[am11]

Yup, those instructions apply only to clang, because this argument is not supported on gcc:

runtime/src/coreclr/nativeaot/BuildIntegration/Microsoft.NETCore.Native.Unix.targets

Line 91 in 0eabf7f

<LinkerArg Include="--target=$(TargetTriple)" Condition="'$(TargetOS)' != 'OSX' and '$(TargetTriple)' != ''" />

[WhiteBlackGoose]

I see.
While we're at it, is there anything for OS X that has to be referenced? (I see only windows and linux mentioned in the instruction)

[am11]

macOS is not supported in .NET 7. It is only available in the daily builds of .NET 8. We can update the document. Basically only cross-architecture is supported on OSX (not linux to osx). For example on M1 machine (osx-arm64), we can use:

$ dotnet8 publish -p:PublishAot=true --arch x64

to cross-compile x64 binary.

[WhiteBlackGoose]

macOS is not supported in .NET 7

Without cross-compilation it works though 🤔

[am11]

Without cross-compilation it works though 🤔

Yes, for osx-x64 but osx-arm64 is only supported in .NET 8.

[WhiteBlackGoose]

Got it. Any reason why btw? It requires additional work or something else?

[WhiteBlackGoose]

Also, is arch-cross-compilation only available in .NET 8?

[am11]

osx-arm64 support was implemented in #75264 (merged three days before the 7.0 RC1 release), and number of fixes went in main branch after that. Normally new platform support PRs are not backported, when there was no time spent on testing during the development cycle.

Also, is arch-cross-compilation only available in .NET 8?

Yes, because for OSX we only support cross-architecture compilation (and not cross-OS compilation), so it was not necessary when only one architecture was supported.

[WhiteBlackGoose]

I mean, what about other OS? Is there arch-cross-compilation for linux on .NET 7?

[am11]

Yes. On linux, cross-compilation is supported with clang only. Normal compilation is supported with both clang and gcc.