iOS (and probably other AOT platforms) needs to have delegates registered

 - if a managed delegate is going to be passed to native code, then it requires an attribute
 - instead of depending on Xamarin.iOS for this, we can just create our own, the iOS runtime just checks for the type name
 - reference: https://docs.microsoft.com/en-gb/xamarin/ios/internals/limitations#reverse-callbacks

1 files changed, 12 insertions, 0 deletions

diff --git a/src/csharp/Grpc.Core/Internal/NativeLogRedirector.cs b/src/csharp/Grpc.Core/Internal/NativeLogRedirector.cs
index bf6440123a..72dd21dc94 100644
--- a/src/csharp/Grpc.Core/Internal/NativeLogRedirector.cs
+++ b/src/csharp/Grpc.Core/Internal/NativeLogRedirector.cs
@@ -51,6 +51,7 @@ namespace Grpc.Core.Internal
             }
         }
 
+        [MonoPInvokeCallback(typeof(GprLogDelegate))]
         private static void HandleWrite(IntPtr fileStringPtr, int line, ulong threadId, IntPtr severityStringPtr, IntPtr msgPtr)
         {
             try
@@ -86,4 +87,15 @@ namespace Grpc.Core.Internal
             }
         }
     }
+
+    [AttributeUsage(AttributeTargets.Method)]
+    internal sealed class MonoPInvokeCallbackAttribute : Attribute
+    {
+        public MonoPInvokeCallbackAttribute(Type type)
+        {
+            Type = type;
+        }
+
+        public Type Type { get; private set; }
+    }
 }