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Fix native memory leak in AsAnyMarshaler.ConvertLayoutToNative on exception #126909

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Fix native memory leak in AsAnyMarshaler.ConvertLayoutToNative on exception #126909

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Copilot Apr 14, 2026
2405c11
Fix native memory leak in AsAnyMarshaler.ConvertLayoutToNative
Copilot Apr 14, 2026
7e6b029
Apply suggestion from @jkoritzinsky
jkoritzinsky Apr 14, 2026
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Merge branch 'main' into copilot/fix-native-memory-leak
jkoritzinsky Jul 20, 2026
cb757ba
Fix names
jkoritzinsky Jul 20, 2026
1c62ca3
Remove redundant comment and add regression test for exception-path c…
Copilot Jul 22, 2026
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13 changes: 11 additions & 2 deletions src/coreclr/System.Private.CoreLib/src/System/StubHelpers.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -972,9 +972,18 @@ public override unsafe IntPtr ConvertToNative(object managed, int dwFlags)
int allocSize = Marshal.SizeOfHelper((RuntimeType)_layoutType, false);
IntPtr pNative = Marshal.AllocCoTaskMem(allocSize);

if (IsIn(dwFlags))
try
{
StubHelpers.LayoutTypeConvertToUnmanaged(managed, (byte*)pNative, ref _cleanupWorkList);
if (IsIn(dwFlags))
{
StubHelpers.LayoutTypeConvertToUnmanaged(managed, (byte*)pNative, ref _cleanupWorkList);
}
}
catch
{
StubHelpers.DestroyCleanupList(ref _cleanupWorkList);
Marshal.FreeCoTaskMem(pNative);
throw;
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}

return pNative;
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11 changes: 11 additions & 0 deletions src/tests/Interop/PInvoke/AsAny/AsAnyTest.cs
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Expand Up @@ -318,6 +318,7 @@ public static int TestEntryPoint()
TestIntPtrArray();
TestUIntPtrArray();
TestLayout();
TestLayoutConvertToNativeExceptionPath();
RunAsAnyFieldTests();
TestUnicodeString();
TestUnicodeStringArray();
Expand Down Expand Up @@ -654,6 +655,16 @@ public static void TestLayout() {
Console.WriteLine("------------------------");
}

private static void TestLayoutConvertToNativeExceptionPath()
{
// AsAnyField contains a field with [MarshalAs(UnmanagedType.AsAny)], which is not
// supported in layout marshaling. When passed via AsAny, LayoutImplementation.ConvertToNative
// allocates a native buffer and then calls LayoutTypeConvertToUnmanaged, which throws
// TypeLoadException. Verify the exception propagates correctly; the fix ensures the
// native buffer is freed on this exception path rather than leaked.
Assert.Throws<TypeLoadException>(() => PassLayout(new AsAnyField()));
}

static void CharArrayInit(char[] unMappableCharArray_In, char[] unMappableCharArray_InOut, char[] unMappableCharArray_Out,
char[] mappableCharArray_In, char[] mappableCharArray_InOut, char[] mappableCharArray_Out,
string unMappableStr, string mappableStr)
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