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Native Blueprint Code generations create wrong includes.

Hello guys, hope this will be helpful :)

Bug description

n my project i tried for the first time the blueprint nativization procedure, and it failed strangely. Digging it, i found out that it was generating the wrong includes for the blueprints.

In fact, it was skipping a parent include for some classes, for example if i had:

  1. C++ class named A

  2. BlueprintClass named B, derived from A

  3. BlueprintClass named C, derived from B

int the C class header it was correctly extending B, but it was including A directly, resulting in a compiling failure (unknown class B).

I had an hard time reproducing it on a fresh project, below you can find the steps.

It's kinda hard to reproduce it, but this way it fails most of the times.

How to reproduce

Note: Since testing it requires packaging, i suggest to disable "Full rebuild": i tested with it too, the result is the same.

Note 2: This steps list will show a setup for a working project, then will show how to mess it up, and how to workaround it.

Tested on 4.15.1-0

Initial setup to a working project:

  • Create a new "C++ Basic Code" project, name it "NativeTesting": Desktop, maximum quality and no starter content

  • Build the newly created project in VS

  • Open the editor

  • Create a new C++ class, based on StaticMeshActor, and call it "MyStaticMeshActor".

  • The following code will be generated, we'll leave it as it is:


   // Fill out your copyright notice in the Description page of Project Settings.
 #pragma once
 #include "Engine/StaticMeshActor.h"
 #include "MyStaticMeshActor.generated.h"
 class NATIVETEST_API AMyStaticMeshActor : public AStaticMeshActor


 // Fill out your copyright notice in the Description page of Project Settings.
 #include "NativeTest.h"
 #include "MyStaticMeshActor.h"

  • Close the editor and recompile

  • Now return to editor, and create a new blueprint class, with "MyStaticMeshActor" as parent, and call it "MyBase". Open it, save, close.

  • Create a new blueprint class, with "MyBase" as parent, and call it "SecondBP". Open it.

  • Add a cube component, save and close.

  • Put it in the level, and save it with name "MyLevel"

  • Open Project Settings, and go to Packaging section

  • Set BuildConfiguration to Development, uncheck "Full Rebuild", and under blueprints set Nativization Method to "Inclusive"

  • Package the project for windows 64: it will work successfully.

Create the problem:

  • Open Project Settings, and go to Packaging section

  • Under blueprints set Nativization Method to "Exclusive"

  • Open "SecondBP", go to class settings and enable "Nativize"

  • Try to package again.

  • it should fail with errors like these:

    UATHelper: Packaging (Windows (64-bit)): UnrealBuildTool: U:\Unreal Projects\NativeTesting\Intermediate\WindowsNoEditor\NativizedAssets\Source\NativizedAssets\Public\SecondBP_pf1010915279.h(8): error C2504: 'AMyBase_Cpf1010915279': base class undefined UATHelper: Packaging (Windows (64-bit)): UnrealBuildTool: U:\Unreal Projects\NativeTesting\Intermediate\WindowsNoEditor\NativizedAssets\Source\NativizedAssets\Public\SecondBP_pf1010915279.h(10): error C3646: 'Super': unknown override specifier

In fact, looking at the generated code, in Intermediate/WindowsNoEditor/NativizedAssets/Source/Public/SecondBP__.h, we have:

 #include "Blueprint/BlueprintSupport.h"
 #include "NativeTesting/MyStaticMeshActor.h"
 class UStaticMeshComponent;
 #include "SecondBP__pf1010915279.generated.h"
 UCLASS(config=Engine, Blueprintable, BlueprintType, meta=(ReplaceConverted="/Game/SecondBP.SecondBP_C", OverrideNativeName="SecondBP_C"))
 class ASecondBP_C__pf1010915279 : public AMyBase_C__pf1010915279


Notice how it's including MyStaticMeshActor.h instead of MyBase_C__pf1010915279.h


  • Open the blueprint "MyBase"

  • Connect something to "BeginPlay", like a "Print String" node, save and close (this will make it a "normal blueprint", not a data-only).

  • Try to package again, it will work.

    Current Behaviour

On exclusive nativization, seems like it fails to generate the correct includes if the parent is a data-only blueprint. In fact, in the SecondBP_.h it places:

 #include "NativeTesting/MyStaticMeshActor.h"

instead of:

 #include "MyBase__pf1010915279.h"

As already stated, it seems directly related to data-only blueprint, but it doesn't happen on an inclusive nativization.

Expected behaviour

It should always generate the correct include (with the right parent class).


I had an hard time tackling this, it seemed pretty randomic, and i lost a lot of time due to the numerous packaging launches.

I noticed that sometimes it still work, but trying around i can always make it fail in the same way (this is the simplest i found).

I hope this can help you, and maybe others that had issues like me, with the workaround.

Let me know if you need more infos :)

Simone Daminato

[edit1] : fixed some typos.

Product Version: UE 4.15
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asked Apr 27 '17 at 07:59 PM in Bug Reports

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1 answer: sort voted first

Hey zamy-

Thank you for submitting a bug report. I have reproduced this issue and logged a report for it here https://issues.unrealengine.com/issue/UE-44488 . You can track the report's status as the issue is reviewed by our development staff. Please be aware that this issue may not be prioritized or fixed soon.


Doug Wilson

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answered Apr 28 '17 at 01:44 PM

avatar image zamy Apr 28 '17 at 02:44 PM

Thanks a lot Doug. I found another small issue of nativization with Arrays of TSubclassOf. Do you prefer if i report it in here or open another thread?

avatar image Doug E ♦♦ STAFF Apr 28 '17 at 02:47 PM

It would be best to create a new post to track each issue separately.

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