Installed 4.26, now no code will compile

Development Programming & Scripting C++
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1

I’ve been trying to solve this for months now and I don’t have any choice but to restart my entire project in Unity, salvaging what little code I could. Ever since I installed 4.26 none of my projects work. No previous or current version will compile any C++ code within any folders. Always gives me this error code;

C:\Project Files\UE4\ExampleProj\Source\ExampleProj\Actors\ExamplePawn.cpp(4): fatal error C1083: Cannot open include file: ‘Actors/ExamplePawn.h’: No such file or directory

Code compiles perfectly fine when not inside any sub-folders. For example ExampleProj\ExamplePawn.cpp would compile fine, but ExampleProj\Actors\ExamplePawn.cpp will not.

I’ve uninstalled Windows and that didn’t work. I’ve uninstalled VS 2019 and that didn’t work. I uninstalled UE4 and that didn’t work. I have no other ideas than buy a new PC and hope, or just stop using UE4.

2

  1. What version are you upgrading from?

  2. Does auto complete when trying to include a file give any hints as to what is missing? You could try including with or without the ExampleProj as a prefix. So try both #include "ExampleProj/Actors/ExamplePawn.h" and #include "Actors/ExamplePawn.h"

  3. In your Build.cs, you can try setting bLegacyPublicIncludePaths = true to see if that helps. I would try #2 both with and without this part, as this build option can affect which paths will compile or not.

3

After resetting Windows the error only happened on 4.26, before it was on any version. Setting bLegacyPublicIncludePaths = true fixed the issue. Is it bad practice to include code outside Public / Private paths?

4

Oh okay. Thanks! I tried extending the include path first (as that’s the line the error sites, obviously) but it didn’t change anything. Tried ExampleProj/Actors/… , with the full folder path, and with various other configurations. None helped.

5

When bLegacyPublicIncludePaths = false, UE omits subfolders from public include paths to reduce compiler command line length. The main impact that I have seen from it is that, when false, you need to specify the path more explicitly, which is why I suggested trying #include "ExampleProj/... before changing this.

With the setting turned on, you may run into issues with the compiler command line being too long (which was my issue and how I found out about this), but it defaulted to true in 4.24 and previous versions, so I think it is mostly an option for you to decide, not better or worse practice one way or the other.