Allow emitting line number information into native AOT apps #122227

MichalStrehovsky · 2025-12-05T14:40:30Z

Fixes #121093 (because I needed more precise tracking of what gets stack trace data)
Fixes #68714

Submitting as draft for now:

Doesn't implement reading this data at runtime yet
This should be opt-in, not on by default if we have stack traces (we've had an issue tracking this for a long time and there's some but not huge demand)

Embeds line number data into executable (avoids having to carry PDB/DWO/DSYM, and writing parsers for those)
The data is emitted into a separate hashtable that hashes two different things based on the source of the stack trace data (we carry method stack trace data in reflection metadata and in dedicated stack trace data; for methods that are not targets of reflection). This requires using two mechanisms to do lookups. As to why we use these mechanisms for lookups instead of code addresses: we cannot do hashtables based on code addresses, this would require complex object writer coordination.

Cc @dotnet/ilc-contrib

dotnet-policy-service · 2025-12-05T14:41:29Z

Tagging subscribers to this area: @agocke, @MichalStrehovsky, @jkotas
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Copilot

Pull request overview

This PR adds support for embedding line number information into native AOT applications, allowing stack traces to include file names and line numbers without requiring separate debug symbol files (PDB/DWO/DSYM). The implementation uses hashtables to map methods to their line number data, with two different lookup mechanisms: one for methods with dedicated stack trace metadata and another for methods with reflection metadata.

Key Changes

Introduces StackTraceLineNumbersNode and StackTraceDocumentsNode to embed line number and document information into the executable
Adds HasLineNumbers flag to MethodStackTraceVisibilityFlags and corresponding StackTraceRecordFlags to control line number emission
Extends VersionResilientHashCode with CombineThreeValuesIntoHash method for hashing three values

Reviewed changes

Copilot reviewed 13 out of 13 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
`src/tests/nativeaot/SmokeTests/Reflection/Reflection.cs`	Adds regression test for issue #121093 validating stack trace contains method names for both reflected and non-reflected generic methods
`src/libraries/Common/src/Internal/VersionResilientHashCode.cs`	Adds `CombineThreeValuesIntoHash` method for creating stable hash codes from three values
`src/coreclr/tools/aot/ILCompiler/Program.cs`	Updates stack trace emission policy to enable line numbers when stack trace data is emitted
`src/coreclr/tools/aot/ILCompiler.Compiler/ILCompiler.Compiler.csproj`	Adds new node files to project
`src/coreclr/tools/aot/ILCompiler.Compiler/Compiler/UsageBasedMetadataManager.cs`	Updates `ComputeMetadata` signature to include reflection-based stack trace mappings
`src/coreclr/tools/aot/ILCompiler.Compiler/Compiler/StackTraceEmissionPolicy.cs`	Adds `HasLineNumbers` flag support and constructor parameter to control line number inclusion
`src/coreclr/tools/aot/ILCompiler.Compiler/Compiler/MetadataManager.cs`	Refactors stack trace mapping to support both regular and reflection-based line number generation, adds flag-based filtering
`src/coreclr/tools/aot/ILCompiler.Compiler/Compiler/DependencyAnalysis/StackTraceMethodMappingNode.cs`	Updates to use flag enum instead of boolean
`src/coreclr/tools/aot/ILCompiler.Compiler/Compiler/DependencyAnalysis/StackTraceLineNumbersNode.cs`	New node that generates hashtable mapping methods to compressed line number data
`src/coreclr/tools/aot/ILCompiler.Compiler/Compiler/DependencyAnalysis/StackTraceDocumentsNode.cs`	New node that stores document paths with offset-based indexing
`src/coreclr/tools/aot/ILCompiler.Compiler/Compiler/AnalysisBasedMetadataManager.cs`	Updates `ComputeMetadata` signature to include reflection-based stack trace mappings
`src/coreclr/tools/Common/Internal/Runtime/MetadataBlob.cs`	Adds blob IDs for line numbers and documents
`src/coreclr/tools/Common/Compiler/DependencyAnalysis/SortableDependencyNode.cs`	Adds ordering entries for new node types

Copilot · 2025-12-05T14:51:03Z

...reclr/tools/aot/ILCompiler.Compiler/Compiler/DependencyAnalysis/StackTraceLineNumbersNode.cs

+                        // is a document number. Otherwise we use NativeOffsetDelta == 0 as a marker that the next
+                        // byte is a document number and not a native offset delta.
+                        if (currentDocument != null)
+                            bw.Write7BitEncodedInt((byte)0);


The cast to (byte)0 is incorrect. Write7BitEncodedInt expects an int parameter, not a byte. This should be bw.Write7BitEncodedInt(0); instead.

Suggested change

bw.Write7BitEncodedInt((byte)0);

bw.Write7BitEncodedInt(0);

Copilot · 2025-12-05T14:51:04Z

src/coreclr/tools/aot/ILCompiler.Compiler/Compiler/MetadataManager.cs

+        public IEnumerable<ReflectionStackTraceMapping> GetReflectionStackTraceMappings(NodeFactory factor)
+        {
+            EnsureMetadataGenerated(factor);


Parameter name inconsistency: the parameter is named factor but should be factory to match the pattern used in other similar methods (e.g., GetStackTraceMapping on line 1030).

Suggested change

public IEnumerable<ReflectionStackTraceMapping> GetReflectionStackTraceMappings(NodeFactory factor)

{

EnsureMetadataGenerated(factor);

public IEnumerable<ReflectionStackTraceMapping> GetReflectionStackTraceMappings(NodeFactory factory)

{

EnsureMetadataGenerated(factory);

Copilot · 2025-12-05T14:51:04Z

src/libraries/Common/src/Internal/VersionResilientHashCode.cs

+
+        public static uint CombineThreeValuesIntoHash(uint value1, uint value2, uint value3)
+        {
+            // This matches the behavior of System.HashCode.Combine(value1, value2) as of the time of authoring


The comment on line 209 is incorrect and appears to be copied from CombineTwoValuesIntoHash. It should say "This matches the behavior of System.HashCode.Combine(value1, value2, value3)" to accurately reflect that it combines three values, not two.

Suggested change

// This matches the behavior of System.HashCode.Combine(value1, value2) as of the time of authoring

// This matches the behavior of System.HashCode.Combine(value1, value2, value3) as of the time of authoring

Copilot · 2025-12-05T14:51:04Z

...reclr/tools/aot/ILCompiler.Compiler/Compiler/DependencyAnalysis/StackTraceLineNumbersNode.cs

+            foreach (StackTraceMapping mapping in factory.MetadataManager.GetStackTraceMapping(factory))
+            {
+                var entrypointSymbol = factory.MethodEntrypoint(mapping.Method);
+                if (entrypointSymbol is not INodeWithDebugInfo debugInfo)
+                    continue;
+
+                BlobVertex blob = CreateLineNumbersBlob(_documents, debugInfo);
+                if (blob == null)
+                    continue;
+
+                Vertex methodPointer = nativeWriter.GetUnsignedConstant(_externalReferences.GetIndex(entrypointSymbol));
+                var hashtableEntry = nativeWriter.GetTuple(methodPointer, blob);
+
+                uint hashcode = VersionResilientHashCode.CombineThreeValuesIntoHash((uint)mapping.OwningTypeHandle, (uint)mapping.MethodNameHandle, (uint)mapping.MethodSignatureHandle);
+                hashtable.Append(hashcode, nativeSection.Place(hashtableEntry));
+            }


Missing flag check: The loop should verify that (mapping.Flags & StackTraceRecordFlags.HasLineNumbers) != 0 before attempting to generate line numbers. Currently, it will attempt to generate line numbers for all methods in the stack trace mapping, regardless of whether the HasLineNumbers flag is set. This could result in generating line numbers for methods where line number emission was not intended according to the policy.

MichalStrehovsky added 3 commits December 3, 2025 05:32

Simplify

c6b2714

Fix 121093

50e1e2f

Writer part

49bb20d

Copilot AI review requested due to automatic review settings December 5, 2025 14:40

MichalStrehovsky added the area-NativeAOT-coreclr label Dec 5, 2025

dotnet-policy-service bot assigned MichalStrehovsky Dec 5, 2025

MichalStrehovsky marked this pull request as draft December 5, 2025 14:41

Copilot started reviewing on behalf of MichalStrehovsky December 5, 2025 14:41 View session

Copilot finished reviewing on behalf of MichalStrehovsky December 5, 2025 14:44

Copilot AI reviewed Dec 5, 2025

View reviewed changes

build-analysis bot mentioned this pull request Dec 5, 2025

System.Security.Cryptography.Tests .IsSupported_AgreesWithPlatform failures #122228

Open

Small cleanup

3d132fa

github-actions bot mentioned this pull request Dec 5, 2025

122227 MichalStrehovsky/rt-sz#199

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Allow emitting line number information into native AOT apps #122227

Allow emitting line number information into native AOT apps #122227

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	// This matches the behavior of System.HashCode.Combine(value1, value2) as of the time of authoring
	// This matches the behavior of System.HashCode.Combine(value1, value2, value3) as of the time of authoring

Allow emitting line number information into native AOT apps #122227

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Pull request overview

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