generic version of StructureToPtr can't work on il2cpp build

Code (CSharp):

1. public static void WriteMarshalUnsafe<TStruct>(TStruct structure,  byte[] bytedata)
2. {
3.        unsafe
4.        {
5.             fixed (byte* byteArrayPtr = &bytedata[0])
6.             {
7.                 Marshal.StructureToPtr<TStruct>(structure, (IntPtr)(byteArrayPtr), true);
8.             }
9.         }
10.   }

Above code works perfectly in mono, but when I build windows il2cpp, some error occur say that "specific object must not be a generic type" during runtime. It's weird. I used to test the generic method of StructureToPtr under il2cpp, and it works fine. I dig into https://docs.unity3d.com/Manual/ScriptingRestrictions.html, but nothing I could found about this.

After some testing, I found the reason. When I pass any POD type as TStruct parameter, it works fine under il2cpp. But I try something hard like this(to get off GC):

Code (CSharp):

1. public class WrapClass<TStruct> where TStruct : struct
2. { public TStruct data; }

I pass the WrapClass instance to WriteMarshalUnsafe, and the error occur under il2cpp.
If the structure parameter is an instance of a generic type(like WrapClass), it can't work.

I have test it on Unity 2019.3.5, Unity 2020.2.0a13.

 

@JoshPeterson Thanks for reply. It realy help. I used Unity 2019.3.5.0f1. I will test it on Unity 2019.4lts，and 2020.2.

 

@JoshPeterson I test it in unity 2020.2.0a13.1691, still can't work, the error say "the specified object must not be an instance of a generic type".

 

When you past a simple POD struct(not generic instance) to StructureToPtr, it call GC. Actually, generic version of StructureToPtr just call StructureToPtr(object t, ....). So, if you pass a struct to StructureToPtr, and it doesn't call GC(actually it does)，then we don't need a WrapClass.