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Value types may generate Dispose (#1787)
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@Saalvage
Saalvage authored Oct 23, 2023
1 parent 3b2a15d commit b14038a
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Showing 2 changed files with 77 additions and 36 deletions.
110 changes: 74 additions & 36 deletions src/Generator/Generators/CSharp/CSharpSources.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -781,7 +781,7 @@ public override void GenerateClassSpecifier(Class @class)
}
}

if (@class.IsGenerated && isBindingGen && @class.IsRefType && !@class.IsOpaque)
if (@class.IsGenerated && isBindingGen && NeedsDispose(@class) && !@class.IsOpaque)
{
bases.Add("IDisposable");
}
Expand All @@ -790,6 +790,12 @@ public override void GenerateClassSpecifier(Class @class)
Write(" : {0}", string.Join(", ", bases));
}

private bool NeedsDispose(Class @class)
{
return @class.IsRefType || @class.IsValueType &&
(@class.GetConstCharFieldProperties().Any() || @class.HasNonTrivialDestructor);
}

private bool CanUseSequentialLayout(Class @class)
{
if (@class.IsUnion || @class.HasUnionFields)
Expand Down Expand Up @@ -2223,25 +2229,24 @@ public void GenerateClassConstructors(Class @class)
GenerateMethod(ctor, @class);
}

if (@class.IsRefType)
{
// We used to always call GenerateClassFinalizer here. However, the
// finalizer calls Dispose which is conditionally implemented below.
// Instead, generate the finalizer only if Dispose is also implemented.
// We used to always call GenerateClassFinalizer here. However, the
// finalizer calls Dispose which is conditionally implemented below.
// Instead, generate the finalizer only if Dispose is also implemented.

// ensure any virtual dtor in the chain is called
var dtor = @class.Destructors.FirstOrDefault(d => d.Access != AccessSpecifier.Private);
if (ShouldGenerateClassNativeField(@class) ||
(dtor != null && (dtor.IsVirtual || @class.HasNonTrivialDestructor)) ||
// virtual destructors in abstract classes may lack a pointer in the v-table
// so they have to be called by symbol; thus we need an explicit Dispose override
@class.IsAbstract)
if (!@class.IsOpaque)
{
// ensure any virtual dtor in the chain is called
var dtor = @class.Destructors.FirstOrDefault(d => d.Access != AccessSpecifier.Private);
if (ShouldGenerateClassNativeField(@class) ||
(dtor != null && (dtor.IsVirtual || @class.HasNonTrivialDestructor)) ||
// virtual destructors in abstract classes may lack a pointer in the v-table
// so they have to be called by symbol; thus we need an explicit Dispose override
@class.IsAbstract)
if (!@class.IsOpaque)
{
if (@class.IsRefType)
GenerateClassFinalizer(@class);
if (NeedsDispose(@class))
GenerateDisposeMethods(@class);
}
}
}
}

private void GenerateClassFinalizer(Class @class)
Expand All @@ -2250,19 +2255,23 @@ private void GenerateClassFinalizer(Class @class)
return;

using (PushWriteBlock(BlockKind.Finalizer, $"~{@class.Name}()", NewLineKind.BeforeNextBlock))
WriteLine($"Dispose(false, callNativeDtor : {Helpers.OwnsNativeInstanceIdentifier} );");
WriteLine($"Dispose(false, callNativeDtor: {Helpers.OwnsNativeInstanceIdentifier});");
}

private void GenerateDisposeMethods(Class @class)
{
var hasBaseClass = @class.HasBaseClass && @class.BaseClass.IsRefType;

var hasDtorParam = @class.IsRefType;

// Generate the IDispose Dispose() method.
if (!hasBaseClass)
{
using (PushWriteBlock(BlockKind.Method, "public void Dispose()", NewLineKind.BeforeNextBlock))
{
WriteLine($"Dispose(disposing: true, callNativeDtor : {Helpers.OwnsNativeInstanceIdentifier} );");
WriteLine(hasDtorParam
? $"Dispose(disposing: true, callNativeDtor: {Helpers.OwnsNativeInstanceIdentifier});"
: "Dispose(disposing: true);");
if (Options.GenerateFinalizerFor(@class))
WriteLine("GC.SuppressFinalize(this);");
}
Expand All @@ -2276,7 +2285,10 @@ private void GenerateDisposeMethods(Class @class)

// Generate Dispose(bool, bool) method
var ext = !@class.IsValueType ? (hasBaseClass ? "override " : "virtual ") : string.Empty;
using var _ = PushWriteBlock(BlockKind.Method, $"internal protected {ext}void Dispose(bool disposing, bool callNativeDtor )", NewLineKind.BeforeNextBlock);
var protectionLevel = @class.IsValueType ? "private" : "internal protected";
using var _ = PushWriteBlock(BlockKind.Method,
$"{protectionLevel} {ext}void Dispose(bool disposing{(hasDtorParam ? ", bool callNativeDtor" : "")})",
NewLineKind.BeforeNextBlock);

if (@class.IsRefType)
{
Expand Down Expand Up @@ -2323,7 +2335,7 @@ private void GenerateDisposeMethods(Class @class)
// instance from the NativeToManagedMap. Of course, this is somewhat half-hearted
// since we can't/don't do this when there's no virtual dtor available to detour.
// Anyway, we must be able to call the native dtor in this case even if we don't
/// own the underlying native instance.
// own the underlying native instance.
//
// 2. When we we pass a disposable object to a function "by value" then the callee
// calls the dtor on the argument so our marshalling code must have a way from preventing
Expand All @@ -2335,41 +2347,67 @@ private void GenerateDisposeMethods(Class @class)
// }
//
// IDisposable.Dispose() and Object.Finalize() set callNativeDtor = Helpers.OwnsNativeInstanceIdentifier
WriteLine("if (callNativeDtor)");
if (@class.IsDependent || dtor.IsVirtual)
WriteOpenBraceAndIndent();
else
Indent();
if (hasDtorParam)
{
WriteLine("if (callNativeDtor)");
if (@class.IsDependent || dtor.IsVirtual)
WriteOpenBraceAndIndent();
else
Indent();
}

if (dtor.IsVirtual)
this.GenerateMember(@class, c => GenerateDestructorCall(
c is ClassTemplateSpecialization ?
c.Methods.First(m => m.InstantiatedFrom == dtor) : dtor));
else
this.GenerateMember(@class, c => GenerateMethodBody(c, dtor));
if (@class.IsDependent || dtor.IsVirtual)
UnindentAndWriteCloseBrace();
else
Unindent();

if (hasDtorParam)
{
if (@class.IsDependent || dtor.IsVirtual)
UnindentAndWriteCloseBrace();
else
Unindent();
}
}
}

// If we have any fields holding references to unmanaged memory allocated here, free the
// referenced memory. Don't rely on testing if the field's IntPtr is IntPtr.Zero since
// unmanaged memory isn't always initialized and/or a reference may be owned by the
// native side.
//

string ptr;
if (@class.IsValueType)
{
ptr = $"{Helpers.InstanceIdentifier}Ptr";
WriteLine($"fixed ({Helpers.InternalStruct}* {ptr} = &{Helpers.InstanceIdentifier})");
WriteOpenBraceAndIndent();
}
else
{
ptr = $"(({Helpers.InternalStruct}*){Helpers.InstanceIdentifier})";
}

foreach (var prop in @class.GetConstCharFieldProperties())
{
string name = prop.Field.OriginalName;
var ptr = $"(({Helpers.InternalStruct}*){Helpers.InstanceIdentifier})->{name}";
WriteLine($"if (__{name}_OwnsNativeMemory)");
WriteLineIndent($"Marshal.FreeHGlobal({ptr});");
WriteLineIndent($"Marshal.FreeHGlobal({ptr}->{name});");
}

WriteLine("if ({0})", Helpers.OwnsNativeInstanceIdentifier);
WriteLineIndent("Marshal.FreeHGlobal({0});", Helpers.InstanceIdentifier);
if (@class.IsValueType)
{
UnindentAndWriteCloseBrace();
}
else
{
WriteLine("if ({0})", Helpers.OwnsNativeInstanceIdentifier);
WriteLineIndent("Marshal.FreeHGlobal({0});", Helpers.InstanceIdentifier);

WriteLine("{0} = IntPtr.Zero;", Helpers.InstanceIdentifier);
WriteLine("{0} = IntPtr.Zero;", Helpers.InstanceIdentifier);
}
}

private bool GenerateDestructorCall(Method dtor)
Expand Down
3 changes: 3 additions & 0 deletions tests/dotnet/CSharp/CSharp.Tests.cs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -2034,6 +2034,7 @@ public void TestValueTypeStringMember()
test.CharPtrMember = "test2";
Assert.AreEqual("test", test.StringMember);
Assert.AreEqual("test2", test.CharPtrMember);
test.Dispose();
}

[Test]
Expand All @@ -2047,6 +2048,7 @@ public void TestValueTypeStringMemberDefaulted()
test.CharPtrMember = "test2";
Assert.AreEqual("test", test.StringMember);
Assert.AreEqual("test2", test.CharPtrMember);
test.Dispose();
}

[Test]
Expand All @@ -2059,5 +2061,6 @@ public void TestValueTypeStringMemberDefaultedCtor()
test.CharPtrMember = "test2";
Assert.AreEqual("test", test.StringMember);
Assert.AreEqual("test2", test.CharPtrMember);
test.Dispose();
}
}

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