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Fix to allow AOT compilers to play nicely with reflection #4559

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merged 1 commit into from Apr 27, 2018
Merged

Fix to allow AOT compilers to play nicely with reflection #4559

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24 changes: 24 additions & 0 deletions csharp/src/Google.Protobuf/Reflection/FileDescriptor.cs
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Expand Up @@ -30,6 +30,7 @@
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
#endregion

using Google.Protobuf.WellKnownTypes;
using System;
using System.Collections.Generic;
using System.Collections.ObjectModel;
Expand All @@ -43,6 +44,16 @@ namespace Google.Protobuf.Reflection
/// </summary>
public sealed class FileDescriptor : IDescriptor
{
// Prevent linker failures when using IL2CPP with the well-known types.
static FileDescriptor()
{
ForceReflectionInitialization<Syntax>();
ForceReflectionInitialization<NullValue>();
ForceReflectionInitialization<Field.Types.Cardinality>();
ForceReflectionInitialization<Field.Types.Kind>();
ForceReflectionInitialization<Value.KindOneofCase>();
}

private FileDescriptor(ByteString descriptorData, FileDescriptorProto proto, FileDescriptor[] dependencies, DescriptorPool pool, bool allowUnknownDependencies, GeneratedClrTypeInfo generatedCodeInfo)
{
SerializedData = descriptorData;
Expand Down Expand Up @@ -334,5 +345,18 @@ public override string ToString()
/// The (possibly empty) set of custom options for this file.
/// </summary>
public CustomOptions CustomOptions => Proto.Options?.CustomOptions ?? CustomOptions.Empty;

/// <summary>
/// Performs initialization for the given generic type argument.
/// </summary>
/// <remarks>
/// This method is present for the sake of AOT compilers. It allows code (whether handwritten or generated)
/// to make calls into the reflection machinery of this library to express an intention to use that type
/// reflectively (e.g. for JSON parsing and formatting). The call itself does almost nothing, but AOT compilers
/// attempting to determine which generic type arguments need to be handled will spot the code path and act
/// accordingly.
/// </remarks>
/// <typeparam name="T">The type to force initialization for.</typeparam>
public static void ForceReflectionInitialization<T>() => ReflectionUtil.ForceInitialize<T>();
}
}
41 changes: 23 additions & 18 deletions csharp/src/Google.Protobuf/Reflection/ReflectionUtil.cs
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Expand Up @@ -50,6 +50,29 @@ namespace Google.Protobuf.Reflection
/// </summary>
internal static class ReflectionUtil
{
static ReflectionUtil()
{
ForceInitialize<string>(); // Handles all reference types
ForceInitialize<int>();
ForceInitialize<long>();
ForceInitialize<uint>();
ForceInitialize<ulong>();
ForceInitialize<float>();
ForceInitialize<double>();
ForceInitialize<bool>();
ForceInitialize<int?>();
ForceInitialize<long?>();
ForceInitialize<uint?>();
ForceInitialize<ulong?>();
ForceInitialize<float?>();
ForceInitialize<double?>();
ForceInitialize<bool?>();
ForceInitialize<SampleEnum>();
SampleEnumMethod();
}

internal static void ForceInitialize<T>() => new ReflectionHelper<IMessage, T>();

/// <summary>
/// Empty Type[] used when calling GetProperty to force property instead of indexer fetching.
/// </summary>
Expand Down Expand Up @@ -163,7 +186,6 @@ private static bool CheckCanConvertEnumFuncToInt32Func()
{
try
{
PreventLinkerFailures();
// Try to do the conversion using reflection, so we can see whether it's supported.
MethodInfo method = typeof(ReflectionUtil).GetMethod(nameof(SampleEnumMethod));
// If this passes, we're in a reasonable runtime.
Expand All @@ -176,23 +198,6 @@ private static bool CheckCanConvertEnumFuncToInt32Func()
}
}

/// <summary>
/// This method is effectively pointless, but only called once. It's present (and called)
/// to avoid the Unity linker from removing code that's only called via reflection.
/// </summary>
private static void PreventLinkerFailures()
{
// Exercise the method directly. This should avoid any pro-active linkers from stripping
// the method out.
SampleEnum x = SampleEnumMethod();
if (x != SampleEnum.X)
{
throw new InvalidOperationException("Failure in reflection utilities");
}
// Make sure the ReflectionHelper parameterless constructor isn't removed...
var helper = new ReflectionHelper<int, int>();
}

public enum SampleEnum
{
X
Expand Down