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Implement ISOSDacInterface::GetObjectClassName in cDAC SOSDacImpl #124816

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Implement ISOSDacInterface::GetObjectClassName in cDAC SOSDacImpl #124816

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5174f82
Initial plan
Copilot Feb 24, 2026
e44c530
Implement ISOSDacInterface::GetObjectClassName in SOSDacImpl.cs with …
Copilot Feb 24, 2026
0239f9f
Address review feedback: rename variables, remove free object special…
Copilot Feb 24, 2026
7e6f823
Revert @object back to objectContract variable name
Copilot Feb 24, 2026
89f489f
fix
Feb 24, 2026
f01248c
Merge branch 'main' into copilot/implement-get-object-class-name
max-charlamb Feb 25, 2026
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65 changes: 64 additions & 1 deletion src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Legacy/SOSDacImpl.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -2641,7 +2641,70 @@ int ISOSDacInterface.GetNestedExceptionData(ClrDataAddress exception, ClrDataAdd
}

int ISOSDacInterface.GetObjectClassName(ClrDataAddress obj, uint count, char* className, uint* pNeeded)
=> _legacyImpl is not null ? _legacyImpl.GetObjectClassName(obj, count, className, pNeeded) : HResults.E_NOTIMPL;
{
int hr = HResults.S_OK;
try
{
if (obj == 0)
throw new ArgumentException();

Contracts.IObject objectContract = _target.Contracts.Object;
Contracts.IRuntimeTypeSystem rts = _target.Contracts.RuntimeTypeSystem;
Contracts.ILoader loader = _target.Contracts.Loader;

TargetPointer mt = objectContract.GetMethodTableAddress(obj.ToTargetPointer(_target));
Contracts.TypeHandle typeHandle = rts.GetTypeHandle(mt);

TargetPointer modulePointer = rts.GetModule(typeHandle);
Contracts.ModuleHandle moduleHandle = loader.GetModuleHandleFromModulePtr(modulePointer);
if (!loader.TryGetLoadedImageContents(moduleHandle, out _, out _, out _))
{
OutputBufferHelpers.CopyStringToBuffer(className, count, pNeeded, "<Unloaded Type>");
}
else
{
StringBuilder classNameBuilder = new();
try
{
TypeNameBuilder.AppendType(_target, classNameBuilder, typeHandle, TypeNameFormat.FormatNamespace | TypeNameFormat.FormatFullInst);
}
catch
{
string? fallbackName = _target.Contracts.DacStreams.StringFromEEAddress(mt);
if (fallbackName != null)
{
classNameBuilder.Clear();
classNameBuilder.Append(fallbackName);
}
}
OutputBufferHelpers.CopyStringToBuffer(className, count, pNeeded, classNameBuilder.ToString());
}
}
catch (System.Exception ex)
{
hr = ex.HResult;
}

#if DEBUG
if (_legacyImpl is not null)
{
char[] classNameLocal = new char[count];
uint neededLocal;
int hrLocal;
fixed (char* ptr = classNameLocal)
{
hrLocal = _legacyImpl.GetObjectClassName(obj, count, ptr, &neededLocal);
}
Debug.Assert(hrLocal == hr, $"cDAC: {hr:x}, DAC: {hrLocal:x}");
if (hr == HResults.S_OK)
{
Debug.Assert(pNeeded == null || *pNeeded == neededLocal);
Debug.Assert(className == null || new ReadOnlySpan<char>(classNameLocal, 0, (int)neededLocal - 1).SequenceEqual(new string(className)));
}
}
#endif
return hr;
}

int ISOSDacInterface.GetObjectData(ClrDataAddress objAddr, DacpObjectData* data)
{
Expand Down
40 changes: 40 additions & 0 deletions src/native/managed/cdac/tests/DumpTests/RuntimeTypeSystemDumpTests.cs
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Expand Up @@ -253,4 +253,44 @@ public void RuntimeTypeSystem_ObjectMethodTableHasIntroducedMethods(TestConfigur
Assert.Equal(0x06000000u, token & 0xFF000000u);
}
}

[ConditionalTheory]
[MemberData(nameof(TestConfigurations))]
public void RuntimeTypeSystem_ObjectMethodTableHasLoadedModule(TestConfiguration config)
{
InitializeDumpTest(config);
IRuntimeTypeSystem rts = Target.Contracts.RuntimeTypeSystem;
ILoader loader = Target.Contracts.Loader;

TargetPointer objectMTGlobal = Target.ReadGlobalPointer("ObjectMethodTable");
TargetPointer objectMT = Target.ReadPointer(objectMTGlobal);
TypeHandle handle = rts.GetTypeHandle(objectMT);

TargetPointer modulePointer = rts.GetModule(handle);
Assert.NotEqual(TargetPointer.Null, modulePointer);

ModuleHandle moduleHandle = loader.GetModuleHandleFromModulePtr(modulePointer);
bool isLoaded = loader.TryGetLoadedImageContents(moduleHandle, out _, out _, out _);
Assert.True(isLoaded, "System.Object's module should have loaded image contents");
}

[ConditionalTheory]
[MemberData(nameof(TestConfigurations))]
public void RuntimeTypeSystem_StringMethodTableHasLoadedModule(TestConfiguration config)
{
InitializeDumpTest(config);
IRuntimeTypeSystem rts = Target.Contracts.RuntimeTypeSystem;
ILoader loader = Target.Contracts.Loader;

TargetPointer stringMTGlobal = Target.ReadGlobalPointer("StringMethodTable");
TargetPointer stringMT = Target.ReadPointer(stringMTGlobal);
TypeHandle handle = rts.GetTypeHandle(stringMT);

TargetPointer modulePointer = rts.GetModule(handle);
Assert.NotEqual(TargetPointer.Null, modulePointer);

ModuleHandle moduleHandle = loader.GetModuleHandleFromModulePtr(modulePointer);
bool isLoaded = loader.TryGetLoadedImageContents(moduleHandle, out _, out _, out _);
Assert.True(isLoaded, "System.String's module should have loaded image contents");
}
}
113 changes: 113 additions & 0 deletions src/native/managed/cdac/tests/ObjectTests.cs
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Expand Up @@ -3,6 +3,7 @@

using System;
using Microsoft.Diagnostics.DataContractReader.Contracts;
using Microsoft.Diagnostics.DataContractReader.Legacy;
using Moq;
using Xunit;

Expand Down Expand Up @@ -153,4 +154,116 @@ public void ComData(MockTarget.Architecture arch)
}
});
}

[Theory]
[ClassData(typeof(MockTarget.StdArch))]
public void GetObjectClassName_ZeroAddress(MockTarget.Architecture arch)
{
ObjectContractHelper(arch,
(objectBuilder) => { },
(target) =>
{
ISOSDacInterface sosDac = new SOSDacImpl(target, legacyObj: null);
char[] buffer = new char[256];
uint needed;
int hr;
fixed (char* ptr = buffer)
{
hr = sosDac.GetObjectClassName(default, (uint)buffer.Length, ptr, &needed);
}
Assert.NotEqual(HResults.S_OK, hr);
});
}

[Theory]
[ClassData(typeof(MockTarget.StdArch))]
public void GetObjectClassName_UnloadedModule(MockTarget.Architecture arch)
{
TargetPointer TestObjectAddress = default;
TargetPointer TestMethodTableAddress = default;
ObjectContractHelper(arch,
(objectBuilder) =>
{
TargetPointer eeClass = objectBuilder.RTSBuilder.AddEEClass("TestClass", attr: 0, numMethods: 0, numNonVirtualSlots: 0);
TestMethodTableAddress = objectBuilder.RTSBuilder.AddMethodTable("TestClass",
mtflags: default, mtflags2: default, baseSize: objectBuilder.Builder.TargetTestHelpers.ObjectBaseSize,
module: TargetPointer.Null, parentMethodTable: TargetPointer.Null, numInterfaces: 0, numVirtuals: 0);
objectBuilder.RTSBuilder.SetEEClassAndCanonMTRefs(eeClass, TestMethodTableAddress);
TestObjectAddress = objectBuilder.AddObject(TestMethodTableAddress);
},
(target) =>
{
var mockRts = new Mock<IRuntimeTypeSystem>();
TypeHandle handle = new TypeHandle(TestMethodTableAddress);
mockRts.Setup(r => r.GetTypeHandle(TestMethodTableAddress)).Returns(handle);
mockRts.Setup(r => r.GetModule(handle)).Returns(TargetPointer.Null);

var mockLoader = new Mock<ILoader>();
mockLoader.Setup(l => l.GetModuleHandleFromModulePtr(It.IsAny<TargetPointer>())).Returns(default(Contracts.ModuleHandle));
mockLoader.Setup(l => l.TryGetLoadedImageContents(It.IsAny<Contracts.ModuleHandle>(), out It.Ref<TargetPointer>.IsAny, out It.Ref<uint>.IsAny, out It.Ref<uint>.IsAny)).Returns(false);

var mockObject = new Mock<IObject>();
mockObject.Setup(o => o.GetMethodTableAddress(It.IsAny<TargetPointer>())).Returns(TestMethodTableAddress);

((TestPlaceholderTarget)target).SetContracts(Mock.Of<ContractRegistry>(
c => c.Object == mockObject.Object
&& c.RuntimeTypeSystem == mockRts.Object
&& c.Loader == mockLoader.Object));

ISOSDacInterface sosDac = new SOSDacImpl(target, legacyObj: null);
char[] buffer = new char[256];
uint needed;
int hr;
fixed (char* ptr = buffer)
{
hr = sosDac.GetObjectClassName(new ClrDataAddress(TestObjectAddress.Value), (uint)buffer.Length, ptr, &needed);
}
Assert.Equal(HResults.S_OK, hr);
Assert.Equal((uint)"<Unloaded Type>".Length + 1, needed);
Assert.Equal("<Unloaded Type>", new string(buffer, 0, (int)needed - 1));
});
}

[Theory]
[ClassData(typeof(MockTarget.StdArch))]
public void GetObjectClassName_NullBufferReturnsNeededSize(MockTarget.Architecture arch)
{
TargetPointer TestObjectAddress = default;
TargetPointer TestMethodTableAddress = default;
ObjectContractHelper(arch,
(objectBuilder) =>
{
TargetPointer eeClass = objectBuilder.RTSBuilder.AddEEClass("TestClass", attr: 0, numMethods: 0, numNonVirtualSlots: 0);
TestMethodTableAddress = objectBuilder.RTSBuilder.AddMethodTable("TestClass",
mtflags: default, mtflags2: default, baseSize: objectBuilder.Builder.TargetTestHelpers.ObjectBaseSize,
module: TargetPointer.Null, parentMethodTable: TargetPointer.Null, numInterfaces: 0, numVirtuals: 0);
objectBuilder.RTSBuilder.SetEEClassAndCanonMTRefs(eeClass, TestMethodTableAddress);
TestObjectAddress = objectBuilder.AddObject(TestMethodTableAddress);
},
(target) =>
{
var mockRts = new Mock<IRuntimeTypeSystem>();
TypeHandle handle = new TypeHandle(TestMethodTableAddress);
mockRts.Setup(r => r.GetTypeHandle(TestMethodTableAddress)).Returns(handle);
mockRts.Setup(r => r.GetModule(handle)).Returns(TargetPointer.Null);

var mockLoader = new Mock<ILoader>();
mockLoader.Setup(l => l.GetModuleHandleFromModulePtr(It.IsAny<TargetPointer>())).Returns(default(Contracts.ModuleHandle));
mockLoader.Setup(l => l.TryGetLoadedImageContents(It.IsAny<Contracts.ModuleHandle>(), out It.Ref<TargetPointer>.IsAny, out It.Ref<uint>.IsAny, out It.Ref<uint>.IsAny)).Returns(false);

var mockObject = new Mock<IObject>();
mockObject.Setup(o => o.GetMethodTableAddress(It.IsAny<TargetPointer>())).Returns(TestMethodTableAddress);

((TestPlaceholderTarget)target).SetContracts(Mock.Of<ContractRegistry>(
c => c.Object == mockObject.Object
&& c.RuntimeTypeSystem == mockRts.Object
&& c.Loader == mockLoader.Object));

ISOSDacInterface sosDac = new SOSDacImpl(target, legacyObj: null);
uint needed;
int hr = sosDac.GetObjectClassName(new ClrDataAddress(TestObjectAddress.Value), 0, null, &needed);
Assert.Equal(HResults.S_OK, hr);
Assert.Equal((uint)"<Unloaded Type>".Length + 1, needed);
});
}
}
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