.NET 8 RC1 fails to NativeAOT compile when targeting ios-arm64

[lemonmojo]

Description

Up until .NET RC1, NativeAOT compilation worked out of the box when targeting ios-arm64.
This requires adding <PublishAotUsingRuntimePack>true</PublishAotUsingRuntimePack> and <LinkerArg Include="-isysroot /Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Developer/SDKs/iPhoneOS.sdk" /> to the csproj.
Everything else is pretty much standard fare.

Now, since RC1, dotnet publish fails because of linking errors in libicuuc.a related to C++.

As a workaround, one can add <LinkerArg Include="-lc++" /> to the csproj like in the example below.

Reproduction Steps

Running dotnet publish against the following example csproj works fine because -lc++ was re-added using a LinkerArg flag. Removing this line makes the build fail.

<Project Sdk="Microsoft.NET.Sdk">
  <PropertyGroup>
    <TargetFramework>net8.0</TargetFramework>
    <RuntimeIdentifier>ios-arm64</RuntimeIdentifier>
    <PublishAOT>true</PublishAOT>

    <!-- TODO: Temporary workaround for iOS/iOS Simulator support -->
    <PublishAotUsingRuntimePack>true</PublishAotUsingRuntimePack>
  </PropertyGroup>

  <ItemGroup>
    <!-- TODO: Temporary workaround for iOS support -->
    <LinkerArg Include="-isysroot /Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Developer/SDKs/iPhoneOS.sdk" />

    <!-- TODO: Temporary workaround for .NET 8 RC1 which seems to have removed -lc++ from its linker flags -->
    <LinkerArg Include="-lc++" />
  </ItemGroup>
</Project>

Expected behavior

Compiles out of the box.

Actual behavior

Does not compile without adding <LinkerArg Include="-lc++" />.

Regression?

It did work in all .NET 8 previews until RC1.

Known Workarounds

Adding <LinkerArg Include="-lc++" /> to the csproj.

Configuration

.NET 8.0.100-rc.1.23455.8

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

Up until .NET RC1, NativeAOT compilation worked out of the box when targeting ios-arm64.
This requires adding <PublishAotUsingRuntimePack>true</PublishAotUsingRuntimePack> and <LinkerArg Include="-isysroot /Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Developer/SDKs/iPhoneOS.sdk" /> to the csproj.
Everything else is pretty much standard fare.

Now, since RC1, dotnet publish fails because of linking errors in libicuuc.a related to C++.

As a workaround, one can add <LinkerArg Include="-lc++" /> to the csproj like in the example below.

Reproduction Steps

Running dotnet publish against the following example csproj works fine because -lc++ was re-added using a LinkerArg flag. Removing this line makes the build fail.

<Project Sdk="Microsoft.NET.Sdk">
  <PropertyGroup>
    <TargetFramework>net8.0</TargetFramework>
    <RuntimeIdentifier>ios-arm64</RuntimeIdentifier>
    <PublishAOT>true</PublishAOT>

    <!-- TODO: Temporary workaround for iOS/iOS Simulator support -->
    <PublishAotUsingRuntimePack>true</PublishAotUsingRuntimePack>
  </PropertyGroup>

  <ItemGroup>
    <!-- TODO: Temporary workaround for iOS support -->
    <LinkerArg Include="-isysroot /Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Developer/SDKs/iPhoneOS.sdk" />

    <!-- TODO: Temporary workaround for .NET 8 RC1 which seems to have removed -lc++ from its linker flags -->
    <LinkerArg Include="-lc++" />
  </ItemGroup>
</Project>

Expected behavior

Compiles out of the box.

Actual behavior

Does not compile without adding <LinkerArg Include="-lc++" />.

Regression?

It did work in all .NET 8 previews until RC1.

Known Workarounds

Adding <LinkerArg Include="-lc++" /> to the csproj.

Configuration

.NET 8.0.100-rc.1.23455.8

Other information

No response

Author:	lemonmojo
Assignees:	-
Labels:	area-NativeAOT-coreclr
Milestone:	-

Tagging subscribers to 'os-ios': @steveisok, @akoeplinger, @kotlarmilos
See info in area-owners.md if you want to be subscribed.

Issue Details

---

Description

Up until .NET RC1, NativeAOT compilation worked out of the box when targeting ios-arm64.
This requires adding <PublishAotUsingRuntimePack>true</PublishAotUsingRuntimePack> and <LinkerArg Include="-isysroot /Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Developer/SDKs/iPhoneOS.sdk" /> to the csproj.
Everything else is pretty much standard fare.

Now, since RC1, dotnet publish fails because of linking errors in libicuuc.a related to C++.

As a workaround, one can add <LinkerArg Include="-lc++" /> to the csproj like in the example below.

Reproduction Steps

Running dotnet publish against the following example csproj works fine because -lc++ was re-added using a LinkerArg flag. Removing this line makes the build fail.

<Project Sdk="Microsoft.NET.Sdk">
  <PropertyGroup>
    <TargetFramework>net8.0</TargetFramework>
    <RuntimeIdentifier>ios-arm64</RuntimeIdentifier>
    <PublishAOT>true</PublishAOT>

    <!-- TODO: Temporary workaround for iOS/iOS Simulator support -->
    <PublishAotUsingRuntimePack>true</PublishAotUsingRuntimePack>
  </PropertyGroup>

  <ItemGroup>
    <!-- TODO: Temporary workaround for iOS support -->
    <LinkerArg Include="-isysroot /Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Developer/SDKs/iPhoneOS.sdk" />

    <!-- TODO: Temporary workaround for .NET 8 RC1 which seems to have removed -lc++ from its linker flags -->
    <LinkerArg Include="-lc++" />
  </ItemGroup>
</Project>

Expected behavior

Compiles out of the box.

Actual behavior

Does not compile without adding <LinkerArg Include="-lc++" />.

Regression?

It did work in all .NET 8 previews until RC1.

Known Workarounds

Adding <LinkerArg Include="-lc++" /> to the csproj.

Configuration

.NET 8.0.100-rc.1.23455.8

Other information

No response

Author:	lemonmojo
Assignees:	-
Labels:	untriaged, os-ios, area-NativeAOT-coreclr
Milestone:	-

[ivanpovazan]

Hello @lemonmojo I will look into this.

Just for the clarification, the effort is being made towards creating a NativeAOT library for iOS-like platforms (as reported in: #88737), correct?

[lemonmojo]

Hi @ivanpovazan, yes that's correct.

[ivanpovazan]

Thank you for the confirmation.
I managed to reproduce the issue and will open the PR that fixes it soon - the issue is related to recent changes in globalization and ICU support and is reproducible only in library mode, which is currently not officially supported with NativeAOT on iOS.

As a side note: It is also possible to workaround the problem by passing -p:LinkStandardCPlusPlusLibrary=true (or setting this property in the project file) or using invariant globalization via -p:InvariantGlobalization=true

[lemonmojo]

@ivanpovazan Thx for looking into this.

I'm aware that this is an unsupported scenario at the moment. From what I can tell though, with the unit tests I have in place, everything seems to be working properly. Do you happen to know if this is going to be a supported scenario in the future?

Since I'm already passing custom linker flags, I'll keep the workaround I already have in place. But it's good to know that LinkStandardCPlusPlusLibrary exists. I'll keep that in mind.

Also, I know about InvariantGlobalization but it's not a viable option for Beyond.NET.

Kinda off-topic but since you already mentioned ICU related changes: Is the ICU stuff now embedded automatically when building with NativeAOT in library mode for iOS? Or is it still necessary to include the .dat file in the app/framework bundle?

[ivanpovazan]

I'm aware that this is an unsupported scenario at the moment. From what I can tell though, with the unit tests I have in place, everything seems to be working properly. Do you happen to know if this is going to be a supported scenario in the future?

Yes, this is planned to be a supported scenario for .NET9, but at this point, I cannot tell for sure if it is going to be backported to .NET8.

Kinda off-topic but since you already mentioned ICU related changes: Is the ICU stuff now embedded automatically when building with NativeAOT in library mode for iOS? Or is it still necessary to include the .dat file in the app/framework bundle?

It is still necessary to include the data file in the bundle as the file is loaded from a path:

runtime/src/native/libs/System.Globalization.Native/pal_icushim_static.c

Lines 171 to 184 in d40f90c

	GlobalizationNative_LoadICUData(const char* path)
	{
	#if defined(TARGET_MACCATALYST) || defined(TARGET_IOS) || defined(TARGET_TVOS)
	if (path && path[0] != '/')
	{
	// if the path is relative, prepend the app bundle root
	path = GlobalizationNative_GetICUDataPathRelativeToAppBundleRoot(path);
	}
	if (!path)
	{
	// fallback to icudt.dat in the app bundle resources in case the path isn't set
	path = GlobalizationNative_GetICUDataPathFallback();
	}
	#endif

The ICU changes I was referring to were introduced here: https://github.com/dotnet/runtime/pull/90430/files when we started statically linking: icudata, icui18n and icuuc (which depend on standard c++ library) instead of using private APIs when targeting iOS-like platforms. This regression is not visible when building applications, because the app bundlers we are using: AppleAppBuilder and Xamarin are taking care of native linking.

[lemonmojo]

@ivanpovazan Got you! Thx a lot for explaining the details.