[.NET 8] <PublishTrimmed> no longers works but throws build process for an infinite loop

[DierkDroth]

Description

So far I built my ARM64 binary by
dotnet publish -c Release -r linux-arm64 -p:PublishSingleFile=true -p:SelfContained=true -p:PublishReadyToRun=true MyProject.csproj

Here are my project settings:

	<PropertyGroup>
		<OutputType>Exe</OutputType>
		<TargetFramework>net8.0</TargetFramework>
		<VersionPrefix>1.10.14</VersionPrefix>
		<RunAnalyzersDuringLiveAnalysis>False</RunAnalyzersDuringLiveAnalysis>
		<RunAnalyzersDuringBuild>False</RunAnalyzersDuringBuild>
		<EnableNETAnalyzers>False</EnableNETAnalyzers>
		<ProduceReferenceAssembly>False</ProduceReferenceAssembly>
		<PublishTrimmed>true</PublishTrimmed>
	</PropertyGroup>

Turns out <PublishTrimmed>true</PublishTrimmed> no longers works: the build which tools ~3 minutes on .NET 7 now did not terminate the 'optimization phase' after > 9 hours.

What's going wrong and how could I trim my build as before?

Reproduction Steps

Please see above

Expected behavior

Trimming should work with .NET8 as it worked with .NET 7

Actual behavior

Trimming does not work with .NET8 as it worked with .NET 7

Regression?

Yes

Known Workarounds

None

Configuration

No response

Other information

No response

Tagging subscribers to this area: @agocke, @sbomer, @vitek-karas
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Issue Details

---

Description

So far I built my ARM64 binary by
dotnet publish -c Release -r linux-arm64 -p:PublishSingleFile=true -p:SelfContained=true -p:PublishReadyToRun=true MyProject.csproj

Here are my project settings:

	<PropertyGroup>
		<OutputType>Exe</OutputType>
		<TargetFramework>net8.0</TargetFramework>
		<VersionPrefix>1.10.14</VersionPrefix>
		<RunAnalyzersDuringLiveAnalysis>False</RunAnalyzersDuringLiveAnalysis>
		<RunAnalyzersDuringBuild>False</RunAnalyzersDuringBuild>
		<EnableNETAnalyzers>False</EnableNETAnalyzers>
		<ProduceReferenceAssembly>False</ProduceReferenceAssembly>
		<PublishTrimmed>true</PublishTrimmed>
	</PropertyGroup>

Turns out <PublishTrimmed>true</PublishTrimmed> no longers works: the build which tools ~3 minutes on .NET 7 now did not terminate the 'optimization phase' after > 9 hours.

What's going wrong and how could I trim my build as before?

Reproduction Steps

Please see above

Expected behavior

Trimming should work with .NET8 as it worked with .NET 7

Actual behavior

Trimming does not work with .NET8 as it worked with .NET 7

Regression?

Yes

Known Workarounds

None

Configuration

No response

Other information

No response

Author:	DierkDroth
Assignees:	-
Labels:	untriaged, area-Tools-ILLink, needs-area-label
Milestone:	-

[vitek-karas]

Thanks for reporting this. Unfortunately, there's not enough info here to figure out what's going on.

Could you please try some of these:

• Running the "hanging" publish - can you look what process is hanging. I would expect it to be eating CPU cycles instead of just waiting on something. If it's related to trimming it would be a process dotnet.exe and with illink.dll on the command line - but I'm guessing.
• If you find that process, can you try attaching a debugger to it (VS attach debugger would work well for this)? Then break the debugger and look for threads which have something interesting on the callstack - if it's trimming related the code for that lives in Mono.Linker namespace - the callstacks should be safe to share, the trimmer runs only code from the trimmer and the framework, there won't be anything from your project visible on the stack.
• I assume you can't share your project, but maybe you could share the list of NuGet dependencies (it's common that the problem is caused by some code from the NuGet dependencies and those are public, so should not be a problem to share)
• Anything special about your project you can think of? (I know it's a vague question, but you never know)

[DierkDroth]

Thanks for getting back to me @vitek-karas.

Curious: would it help if I attached the untrimmed binary so you could try running the trim logic on it?

[vitek-karas]

We would need all of the input binaries and the trimmer command line. You could try using https://github.com/vitek-karas/illinkrepro. Basically you run your publish with /bl to produce msbuild.binlog. The tool in that repo then parses that and extracts the trimmer command line from it. Then it copies all of the input assemblies into a repro directory and constructs a copy of the command line. If you're comfortable sharing that, it should let me reproduce the failure/hang exactly. The repro will contain all of the input assemblies (not source code, compiled IL) and the command line to trimmer (which may sometimes contains certain local paths).

[DierkDroth]

Thanks @vitek-karas.

To clarify:

• I run the build without the trimming option but with the /bl option
• this creates a msbuild.binlog file

Could I just attach that msbuild.binlog here and you then would have what you needed to further analyze the case?

Note: I already had quite a few support cases/issues with the great Platform UNO team, where I happily shared BINLOG files. That's why I wouldn't have any concern on sharing that file.

Please let me know if you felt that would be a way to go or if I rather should go through the steps you outlined above. Thanks

[vitek-karas]

Small correction:

• You run the publish command which hangs (no changes) just add /bl
• This creates the "interesting" binlog

The binlog is unfortunately not enough - it contains the command line to the trimmer, but not the input assemblies. For that something like the tool from the illinkrepro repo, to collect the input assemblies as well, is needed.

We can also arrange for a more private way of sending this data, if you want. The best way then is to create a Visual Studio Feedback item and attach the data there.

[DierkDroth]

Thanks @vitek-karas. I just created a repo and filed it as Visual Studio Feedback item.

Side note: It would make the handling of your illinkrepo tool more handy if just a single, self-contained file would be created. I had to copy the illinkrepo.* files + all dlls to the target directory.

Please let me know if you needed anything else.