Nativization failed: Error C2679 when nativizing blueprint containing a function with an integer array output that is not connected to an integer array

EDIT: Moved to bug reports with repro steps.

Step 1) Create blank project

Step 2) Create a new blueprint actor and create a function with an integer array output. Do not connect anything to the integer array output. Connect the input exec to the output exec.

Step 3) Enable blueprint nativization

Step 4) Package for Win64

Project will fail to nativize the blueprint with the error mentioned below, and as a result fail to package even though the blueprint compiles successfully.

PS: For anyone encountering a similar error who happens to find this thread, you can track it down by digging through the CPP file that is generated, and going to the line stated in the package log.


Hey. I’m attempting to package my project on 4.17, and I’m running into this error. There’s no errors in my blueprints or the cook log, they all run flawlessly within the editor. I last built this project about a week ago successfully, and while I’ve put in a lot of work since, very little of it was within the blueprint that is apparently causing the error.

This also occurs in the previous engine version, 4.16.3

Here is the error:

UATHelper: Packaging (Windows (64-bit)): UnrealBuildTool: {PROJECT DIRECTORY}\Intermediate\Plugins\WindowsNoEditor\NativizedAssets\Source\NativizedAssets\Private\BP_Grid_Manager__pf2150602248.cpp(14222): error C2679: binary ‘=’: no operator found which takes a right-hand operand of type ‘int’ (or there is no acceptable conversion)

UATHelper: Packaging (Windows (64-bit)): UnrealBuildTool: i:\program files\epic games\ue_4.17\engine\source\runtime\core\public\Containers/Array.h(539): note: could be ‘TArray &TArray::operator =(TArray &&)’
with
[
ElementType=int32
]

i:\program files\epic games\ue_4.17\engine\source\runtime\core\public\Containers/Array.h(414): note: or ‘TArray &TArray::operator =(const TArray &)’
with
[
ElementType=int32
]

i:\program files\epic games\ue_4.17\engine\source\runtime\core\public\Containers/Array.h(382): note: or ‘TArray &TArray::operator =(std::initializer_list)’
with
[
ElementType=int32
]

{PROJECT DIRECTORY}\Intermediate\Plugins\WindowsNoEditor\NativizedAssets\Source\NativizedAssets\Private\BP_Grid_Manager__pf2150602248.cpp(14222): note: while trying to match the argument list ‘(TArray, int)’
with
[
ElementType=int32
]

UATHelper: Packaging (Windows (64-bit)): UnrealBuildTool: ERROR: UBT ERROR: Failed to produce item: {PROJECT DIRECTORY}\Intermediate\Plugins\WindowsNoEditor\NativizedAssets\Binaries\Win64\UE4-NativizedAssets.lib

Hello Selentic,

I was able to reproduce this issue on our end. I have written up a report and I have submitted it to the developers for further consideration. I have provided a link to the public tracker. Please feel free to use the link provided for future updates.

Link: Unreal Engine Issues and Bug Tracker (UE-48397)

Make it a great day