IL2CPP Xcode build error "member access into incomplete type"

Unity Engine
,
1

Hello

I’m using Unity v.5.3.6, and everything was OK, until one day I added some new classes to my project, and Xcode start throwing the following errors:

~my_path~/Classes/Native/Bulk_Assembly-CSharp_2.cpp:177:8: note: forward declaration of ‘Vector2U5BU5D_t2741383957’
struct Vector2U5BU5D_t2741383957;
^
~my_path~/Classes/Native/Bulk_Assembly-CSharp_2.cpp:10983:213: error: member access into incomplete type ‘Vector2U5BU5D_t2741383957’
VirtActionInvoker1< Vector2_t3525329788 >::Invoke(19 /* System.Void System.Collections.Generic.List`1<UnityEngine.Vector2>::Add(!0) /, __this, ((Vector2_t3525329788 )(((((Vector2U5BU5D_t2741383957**)L_0)))->GetAddressAt(static_cast<il2cpp_array_size_t>(L_1)))));
^
~my_path~/Classes/Native/Bulk_Assembly-CSharp_2.cpp:177:8: note: forward declaration of ‘Vector2U5BU5D_t2741383957’
struct Vector2U5BU5D_t2741383957;
^
2 errors generated.

I cut down my project - all assets, textures, scenes, prefabs, postprocessor scripts, etc are removed (there are only *.cs files left), but the error is still here.

BUT When I remove any of *.cs files - error disappeared! It really looks like a black magic

Please advise, how can I find the reason of this error to avoid it now and ever after

Unity ver. 5.3.6p2, Xcode ver. "7.3.1 (7D1014)

2

@WereCrab

This is certainly a bug on the Unity side, as IL2CPP should never generated C++ code that does not compile. It may be pretty difficult for you to track down the cause of this error, unfortunately. I suspect that we will need to debug the il2cpp.exe code generation step to determine how to correct it.

Can you submit a bug report and include the project that causes this issue? If so, please let me know the bug report number, and we’ll correct this. Thanks!

3

I also have this issue and here is case number : 1302459

1 Like
4

@JoshPeterson , Hi Josh. Were you able to take a look at the bug report I have submitted? It is preventing me from building to any platform that requires IL2CPP (All console platforms)

5

Sorry, I’ve not looked at this bug report yet. It seems our QA team is still processing it. I’ll see what I can do to move the processing forward.

6

@castor76 :

Thanks again for the bug report. I’ve started to investigate it now, and we’re working on a fix. In the meantime, you can work around this issue.

The problem is caused by the use of the in modifier on function arguments that are arrays. After I removed a few from the project in the bug report, I was able to get it to compile. I’ll respond via the bug report with specifics about the changes, but I wanted to mention it here for others who might see this.

I expect that we will be able to get this corrected in IL2CPP soon.

7

Thanks for the review. Josh.

There is one thing that I wanted to ask.

You have mentioned that we can remove “in” modifier but would that not cause the array to be passed by copying? ( I could be wrong … ). If so the code behaviour may be the same, but performance wise may not. Am I correct in this?
If it makes no difference at all, then I can just not use “in” modifier at all. Otherwise, I will bring it back once the bug has been addressed.

8

Even without the in modifier, the array will be passed by reference. Some arrays are copied when passed from managed to native code via p/invoke. But for a managed to managed method call like this, the array will not be copied.

9

A bit of additional information on this issue - it turns out that the code also must use the in modifier for an array type on a virtual method to trigger this bug in IL2CPP. If the method is not virtual, the bug will not occur.

10

Good to know!