UE 5.8 Compilation Error

Nerosolis

Problem statement

When compiling my Unreal Engine 5.8 project solution in Visual Studio, the Spine plugin fails to compile at line 59 of SSpineWidget.cpp.

I expected the Spine plugin to compile successfully with Unreal Engine 5.8.

The issue can be reproduced by compiling the project solution in Visual Studio with the Spine plugin enabled.

I was able to fix the issue by manually modifying line 59 of SSpineWidget.cpp.

Runtime information

Spine Runtimes version: 4.3

Unreal Engine version: 5.8.2

SSpineWidget.cpp(59,28): error C2664: 'FName TArray<FName,FDefaultAllocator>::Pop(EAllowShrinking)': cannot convert argument 1 from 'bool' to 'EAllowShrinking'

ResourceName = NamePool.Pop(false);

Spinebot

This looks like a breaking change introduced by Epic in Unreal Engine 5.8, similar to previous UE version updates where Epic changed API signatures. The error occurs because TArray::Pop() no longer accepts a bool argument — instead it now expects an EAllowShrinking enum value.

The fix you found is correct. On line 59 of SSpineWidget.cpp, change:

ResourceName = NamePool.Pop(false);

to:

ResourceName = NamePool.Pop(EAllowShrinking::No);

This is the same kind of "warnings as errors" / API change issue that has affected the Spine UE plugin in past Unreal Engine releases (e.g. UE 5.1.1). Epic periodically introduces breaking changes to their API between engine versions.

You may want to open a GitHub issue at https://github.com/EsotericSoftware/spine-runtimes/issues so the Esoteric Software team is aware and can apply the fix officially in the runtime.

Mario

Thanks for reporting! This is now fixed on the latest 4.3 spine-runtimes branch.

Nerosolis

Mario Thank you!

Unfortunately, I’ve encountered some other issues while using the plugin. I opened a new issue on GitHub: manually re-importing the atlas and skeleton does not update the associated textures 🙁