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[Retained] parameters need to project as pointer #1522

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Merged
merged 1 commit into from
Nov 3, 2025
Merged

[Retained] parameters need to project as pointer #1522

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12 changes: 10 additions & 2 deletions src/Microsoft.Windows.CsWin32/Generator.FriendlyOverloads.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -140,6 +140,7 @@ private IEnumerable<MethodDeclarationSyntax> DeclareFriendlyOverload(MethodDefin
bool isOptional = (param.Attributes & ParameterAttributes.Optional) == ParameterAttributes.Optional;
CustomAttributeHandleCollection paramAttributes = param.GetCustomAttributes();
bool isReserved = this.FindInteropDecorativeAttribute(paramAttributes, "ReservedAttribute") is not null;
bool isRetained = this.FindInteropDecorativeAttribute(paramAttributes, "RetainedAttribute") is not null;
isOptional |= isReserved; // Per metadata decision made at https://github.com/microsoft/win32metadata/issues/1421#issuecomment-1372608090
bool isIn = (param.Attributes & ParameterAttributes.In) == ParameterAttributes.In;
bool isConst = this.FindInteropDecorativeAttribute(paramAttributes, "ConstAttribute") is not null;
Expand All @@ -164,9 +165,16 @@ private IEnumerable<MethodDeclarationSyntax> DeclareFriendlyOverload(MethodDefin
memorySize = DecodeMemorySizeAttribute(memorySizeAttribute);
}

// If there's no MemorySize attribute, we may still need to keep this parameter as a pointer if it's a struct with a flexible array.
if (memorySize is null)
if (isRetained)
{
// Retained means that the callee will keep the pointer beyond this call. To communicate that safety problem to the caller,
// the best we can do is project as a pointer so they know they need to think about it. See https://github.com/microsoft/CsWin32/issues/1066
// and linked issues for more info.
mustRemainAsPointer = true;
}
else if (memorySize is null)
{
// If there's no MemorySize attribute, we may still need to keep this parameter as a pointer if it's a struct with a flexible array.
mustRemainAsPointer = parameterTypeInfo is PointerTypeHandleInfo { ElementType: HandleTypeHandleInfo pointedElement } && pointedElement.Generator.IsStructWithFlexibleArray(pointedElement);
}
else if (!useSpansForPointers)
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1 change: 1 addition & 0 deletions test/CsWin32Generator.Tests/CsWin32GeneratorTests.cs
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Expand Up @@ -171,6 +171,7 @@ public async Task TestGenerateCoCreateableClass()
["SetupDiGetClassInstallParams", "SetupDiGetClassInstallParams", "SafeHandle DeviceInfoSet, winmdroot.Devices.DeviceAndDriverInstallation.SP_DEVINFO_DATA? DeviceInfoData, Span<byte> ClassInstallParams, out uint RequiredSize"],
["IEnumString", "Next", "this winmdroot.System.Com.IEnumString @this, Span<winmdroot.Foundation.PWSTR> rgelt, out uint pceltFetched"],
["PSCreateMemoryPropertyStore", "PSCreateMemoryPropertyStore", "in global::System.Guid riid, out void* ppv"],
["DeviceIoControl", "DeviceIoControl", "SafeHandle hDevice, uint dwIoControlCode, ReadOnlySpan<byte> lpInBuffer, Span<byte> lpOutBuffer, out uint lpBytesReturned, global::System.Threading.NativeOverlapped* lpOverlapped"],
];

[Theory]
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