[release/11.0] Fix NativeAOT thread-static debug info - #133144
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## Summary
- Treat thread-static, GC-static, and non-GC-static fields as mutually
exclusive storage categories when emitting NativeAOT debug types.
- Preserve thread-static fields when the owning type has a generated
thread-static index but no separately generated ordinary GC-static base.
## Problem
`FieldDesc.HasGCStaticBase` returns `true` for NativeAOT thread-static
fields. The debug type writer first accepted a thread-static field based
on `HasThreadStaticBase`, but then independently tested the same field
as an ordinary GC-static field:
```csharp
if (fieldDesc.IsThreadStatic && !hasThreadStatics)
continue;
if (fieldDesc.HasGCStaticBase)
{
if (!hasGcStatics)
continue;
}
```
This dropped all thread-static fields from types that had no separately
generated GC-static base. An example is the `AsyncDispatcherInfo` ref
struct:
```csharp
internal unsafe ref struct AsyncDispatcherInfo
{
// Instance fields omitted.
[ThreadStatic]
internal static AsyncDispatcherInfo* t_current;
}
```
The index symbol was emitted because the type had thread-static storage,
but the PDB omitted the typed parent member, thread-static storage UDT,
helper UDT, and `t_current` field offset.
The fix makes the three storage categories mutually exclusive by
changing the second test to `else if`.
## CDB validation
I built a small runtime-async NativeAOT application that roots
`AsyncDispatcherInfo` and inspected its Windows PDB with CDB.
Before the fix, the index existed only as an untyped symbol. The parent
type had no `__THREADSTATICINDEX`, and the thread-static storage type
did not exist:
```text
0:000> x AsyncDispatcherPdb!S_P_CoreLib_System_Runtime_CompilerServices_AsyncDispatcherInfo::__THREADSTATICINDEX
00007ff7`cd8a7ed8 AsyncDispatcherPdb!S_P_CoreLib_System_Runtime_CompilerServices_AsyncDispatcherInfo::__THREADSTATICINDEX = <no type information>
0:000> dt AsyncDispatcherPdb!S_P_CoreLib_System_Runtime_CompilerServices_AsyncDispatcherInfo
+0x000 Next : Ptr64 S_P_CoreLib_System_Runtime_CompilerServices_AsyncDispatcherInfo
+0x008 NextContinuation : Ptr64 S_P_CoreLib_System_Runtime_CompilerServices_Continuation
+0x010 CurrentTask : Ptr64 S_P_CoreLib_System_Threading_Tasks_Task
+0x018 AsyncProfilerInfo : S_P_CoreLib_System_Runtime_CompilerServices_AsyncProfiler_Info
0:000> dt AsyncDispatcherPdb!__type__THREADSTATICSS_P_CoreLib_System_Runtime_CompilerServices_AsyncDispatcherInfo
Symbol AsyncDispatcherPdb!__type__THREADSTATICSS_P_CoreLib_System_Runtime_CompilerServices_AsyncDispatcherInfo not found.
```
After the fix, the parent UDT has a typed `__THREADSTATICINDEX`, the
storage UDT contains `t_current` at offset `+0x008`, and the helper UDT
is present:
```text
0:000> dt AsyncDispatcherPdb!S_P_CoreLib_System_Runtime_CompilerServices_AsyncDispatcherInfo
+0x000 Next : Ptr64 S_P_CoreLib_System_Runtime_CompilerServices_AsyncDispatcherInfo
+0x008 NextContinuation : Ptr64 S_P_CoreLib_System_Runtime_CompilerServices_Continuation
+0x010 CurrentTask : Ptr64 S_P_CoreLib_System_Threading_Tasks_Task
+0x018 AsyncProfilerInfo : S_P_CoreLib_System_Runtime_CompilerServices_AsyncProfiler_Info
=00007ff6`a5957ed8 __THREADSTATICINDEX : __ThreadStaticHelper<__type__THREADSTATICSS_P_CoreLib_System_Runtime_CompilerServices_AsyncDispatcherInfo>
0:000> dt AsyncDispatcherPdb!__type__THREADSTATICSS_P_CoreLib_System_Runtime_CompilerServices_AsyncDispatcherInfo
+0x000 __VFN_table : Ptr64
+0x000 m_pEEType : Ptr64 S_P_CoreLib_Internal_Runtime_MethodTable
+0x008 t_current : Ptr64 S_P_CoreLib_System_Runtime_CompilerServices_AsyncDispatcherInfo
0:000> dt AsyncDispatcherPdb!__ThreadStaticHelper*AsyncDispatcherInfo*
AsyncDispatcherPdb!__ThreadStaticHelper<__type__THREADSTATICSS_P_CoreLib_System_Runtime_CompilerServices_AsyncDispatcherInfo>
```
## Testing
```text
ILCompiler.Compiler.Tests: Passed 22, Failed 0, Skipped 0
```
> [!NOTE]
> This PR description was generated with GitHub Copilot.
Co-authored-by: Max Charlamb <maxcharlamb@microsoft.com>
Copilot-Session: 32bd0ba5-1c4a-4c99-bdd4-969279117e18
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Contributor
|
Tagging subscribers to this area: @agocke, @dotnet/ilc-contrib |
steveisok
approved these changes
Sep 8, 2026
Member
|
/ba-g Unrelated known issue |
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Backport of #133109 to release/11.0
/cc @max-charlamb
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IMPORTANT: If this backport is for a servicing release, please verify that:
release/X.0-staging, notrelease/X.0.release/X.0(no-stagingsuffix).Package authoring no longer needed in .NET 9
IMPORTANT: Starting with .NET 9, you no longer need to edit a NuGet package's csproj to enable building and bump the version.
Keep in mind that we still need package authoring in .NET 8 and older versions.