dotnet build doesn't terminate in 5.0.200, same code compiles in previous version.

[emmisberger]

Version Used: 5.0.200

Steps to Reproduce:

1. Create an empty C# project (dotnet new console)
2. Run dotnet add package Microsoft.Win32.Registry
3. Replace Program.cs with the following code:

using System.Runtime.InteropServices;
using Microsoft.Win32;

if (RuntimeInformation.IsOSPlatform(OSPlatform.Windows) && Registry.GetValue("", "", null) != null)
{
    foreach (var x in new string[0])
    {
        if ("".ToString() == "")
        {
            try
            {
            }
            catch
            {
            }
        }
    }
}

Expected Behavior:
dotnet build compiles the project

Actual Behavior:
dotnet build hangs indefinitely.

[jaredpar]

This looks to be hanging in the platform compatibility analyzer. Confirmed that disabling analyzers causes the build to succeed.

It's possible that there is a bug in the underlying data flow APIs that is the root here. If so please kick back to compilers.

@mavasani, @jmarolf, @sharwell

[sharwell]

What version of the compiler is included with 5.0.200? I'm not able to reproduce this in the Platform Compatibility Analyzer tests with either 3.8.0 or 3.9.0.

[sharwell]

Here's the test I wrote:

        [Fact]
        [WorkItem(4920, "https://github.com/dotnet/roslyn-analyzers/issues/4920")]
        public async Task FailureToTerminate()
        {
            var source = @"
using System.Runtime.InteropServices;
using Microsoft.Win32;

if (RuntimeInformation.IsOSPlatform(OSPlatform.Windows) && Registry.GetValue("""", """", null) != null)
{
    foreach (var x in new string[0])
    {
        if ("""".ToString() == """")
        {
            try
            {
            }
            catch
            {
            }
        }
    }
}";

            await new VerifyCS.Test
            {
                ReferenceAssemblies = ReferenceAssemblies.Net.Net50.AddPackages(
                    ImmutableArray.Create(new PackageIdentity("Microsoft.Win32.Registry", "5.0.0"))),
                LanguageVersion = CSharpLanguageVersion.CSharp9,
                TestState =
                {
                    OutputKind = OutputKind.ConsoleApplication,
                    Sources = { source },
                    AnalyzerConfigFiles = { ("/.editorconfig", s_msBuildPlatforms) },
                }
            }.RunAsync();
        }

[mavasani]

Tagging @buyaa-n as well in case she is aware of this issue or a fix that was done.

[emmisberger]

@sharwell dotnet csc.dll -v shows me the following:
Microsoft (R) Visual C# Compiler version 3.9.0-5.21120.8 (accdcb77)

[jaredpar]

Here is the project file that I'm using + the global.json

<Project Sdk="Microsoft.NET.Sdk">

  <PropertyGroup>
    <OutputType>Exe</OutputType>
    <TargetFramework>net5.0</TargetFramework>
    <RunAnalyzers>true</RunAnalyzers>
  </PropertyGroup>

  <ItemGroup>
    <PackageReference Include="Microsoft.Win32.Registry" Version="5.0.0" />
  </ItemGroup>

</Project>

{
  "sdk": {
    "version": "5.0.200"
  }
}

Confirmed that this does use 5.0.200 on my machine

C:\Users\jaredpar\temp\console> dotnet --version
5.0.200

[buyaa-n]

Hm, I was not aware of this issue, i can repro with a sample console app. There is something related to Registry.GetValue("""", """", null) != null condition, if I use any other condition it builds just fine

[sharwell]

@jaredpar Can you add a copy of the .globalconfig produced during your test build above? It's generated in the obj/Debug directory.

[sharwell]

Oh, I was finally able to reproduce this by changing the .globalconfig.

[buyaa-n]

Thanks, @sharwell i was able to repro with a similar unit test, it is a very strange edge case, if remove the guard method it builds just fine

// Builds fine
if (Registry.GetValue("", "", null) != null)
{
    foreach (var x in new string[0])
    {
        if ("""".ToString() == """")
        {
            try
            {
            }
            catch
            {
            }
        }
    }
}

If remove any of the blocks inside it also builds (loop or try catch or if condition)

// Builds fine
if (RuntimeInformation.IsOSPlatform(OSPlatform.Windows) && Console.CapsLock)
{
    foreach (var x in new string[0])
    {
        if ("""".ToString() == """")
        {
        }
    }
}

When debug the flow analysis result is not returning, seems flow analysis bug

[sharwell]

@buyaa-n Yeah that comment was outdated. Once I fixed the .globalconfig file I was able to reproduce this and submitted #4923 with the test.

Yes, I also commented today to @mavasani that we need analyzer callbacks for AnalyzerConfig documents in the compiler. Too many cases where lines get silently ignored due problems that could be easily detected and reported by analyzers.

[sharwell]

The test is now merged. The issue is not fixed, but writing the test is tricky so this will hopefully same someone time when they go to investigate this.

[buyaa-n]

@sharwell got it, thanks for the tests

[jaredpar]

Seen at least two instances of this bug pretty much immediately after release. This seems very likely to need to go through servicing.

[Youssef1313]

In DataFlowOperationVisitor put a breakpoint at VisitInvocation. It's called, and finishes executing, then called again, then called again, etc. (that may not be the root cause)

A little bit more down the stack, the following call is done repeatedly:

roslyn-analyzers/src/Utilities/FlowAnalysis/FlowAnalysis/Framework/DataFlow/DataFlowAnalysis.cs

Line 323 in 3fb8781

(TAnalysisData newSuccessorInput, bool isFeasibleBranch) = OperationVisitor.FlowBranch(block, successorWithBranch, AnalysisDomain.Clone(output));

[Youssef1313]

And finally, here is the infinite loop:

roslyn-analyzers/src/Utilities/FlowAnalysis/FlowAnalysis/Framework/DataFlow/DataFlowAnalysis.cs

Line 197 in 3fb8781

while (worklist.Count > 0 || pendingBlocksNeedingAtLeastOnePass.Count > 0)

[nickwhaley]

Worth looking at duplicate dotnet/roslyn#51652 . It fails in older versions also, but with a warning instead of a lockup. In case that helps diagnosis:

Warning AD0001 Analyzer 'Microsoft.NetCore.Analyzers.InteropServices.PlatformCompatibilityAnalyzer' threw an exception of type 'System.ArgumentException' with message 'An element with the same key but a different value already exists. Key: 'Microsoft.CodeAnalysis.Operations.LiteralOperation''.

[mavasani]

I have a fix for this issue: #4928

@jaredpar @terrajobst @jeffhandley @vatsalyaagrawal would this be a candidate for .NET5 servicing fix?

[jaredpar]

There were two reports within the first few days of the SDK being released which speaks a bit about impact to me.

How corner case is the scenario though? It's hard to tell from the bug. If it's decently mainstream I'd vote for pushing through servicing at this point.

[mavasani]

Apparently my fix does not fix the second hang: dotnet/roslyn#51652. I'll continue investigating.

How corner case is the scenario though

Both cases are when there are platform guard checks inside/outside a loop with a try/catch inside a loop.

[mavasani]

Apparently my fix does not fix the second hang: dotnet/roslyn#51652. I'll continue investigating.

Latest commit 44fb5c4 for #4928 fixes dotnet/roslyn#51652.

[nickwhaley]

This problem has reappeared in SDK 5.0.403.

Problem does not exist however in SDK 6.0.100.

[buyaa-n]

There is something wrong with the latest SDK 5.0.403, another bug also reported @jmarolf @mavasani PTAL