Include std C++ headers in UE5.6

Development Programming & Scripting C++
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1

Hello,

I’m trying to build our LiveLink plugin for UE5.6. Unfortunately, standard C++ headers are not found any longer.
That’s fine for the Unreal specific source but the backend of my LiveLink plugin is plain C++ and relies heavily on std C++ headers to be as portable as possible.

For example
include
causes a File not found error.

I can make it compile by manually adding the correct path on my machine to the PrivateIncludePaths in the .Build.cs but then it most likely won’t build in Epic’s build farm, which I need, if I want Epic to distribute our plugin on fab.

Another solution would be to prebuild this backend and ship the binary along with the plugin source code but that will likely cause all kinds of other problems when building for platforms other than Windows.

A third solution is to ship my own copy of std C++ as part of the plugin but that’s at least as ugly as the first two and will likely cause linking issues with duplicate symbols and all.

Up to UE5.5 this has worked nicely.
So they must have changed the build process to not include std C++ include dirs any longer. My hope is that there is some magic build configuration flag that reverts this change and allows me to include standard C++ headers.

Any hints?

thanks,
nils

2

the weird include in the original question was supposed to be

#include <algorithm>
3

I was able to get it to work by adding this to my Build.cs

#if UE_5_6_OR_LATER
IncludeOrderVersion = EngineIncludeOrderVersion.Unreal5_5;
#endif

It’s not a nice solution but it works for now…

4

Hi Nil,
I’m not able to reproduce the issue on my side, what is your compiler version? And what was the command line you use to build your plugin?