Failed to build UE4 from source - error C4426: optimization flags

Development Platform & Builds
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1

Hi,

I got following error during building UE4.11p5 from source at VS2015 Community Update 1:

1> Module.GameplayTasks.cpp
1> Module.GameplayAbilitiesEditor.cpp
1>c:\GIT\UnrealEngine\Engine\Source\Runtime\GameplayTasks\Private\GameplayTask.cpp(3): error C4426: optimization flags changed after including header, may be due to #pragma optimize()c:\GIT\UnrealEngine\Engine\Intermediate\Build\Win64\UE4Editor\Inc\GameplayTasks\GameplayTasks.generated.cpp(8): error C4426: optimization flags changed after including header, may be due to #pragma optimize()
1>
1>c:\GIT\UnrealEngine\Engine\Intermediate\Build\Win64\UE4Editor\Development\GameplayTasks\Module.GameplayTasks.cpp(3): error C4426: optimization flags changed after including header, may be due to #pragma optimize()
1>c:\GIT\UnrealEngine\Engine\Intermediate\Build\Win64\UE4Editor\Development\GameplayAbilitiesEditor\Module.GameplayAbilitiesEditor.cpp(21): error C4426: optimization flags changed after including header, may be due to #pragma optimize()
1> -------- End Detailed Actions Stats -----------------------------------------------------------
1>ERROR : UBT error : Failed to produce item: c:\GIT\UnrealEngine\Engine\Binaries\Win64\UE4Editor-GameplayTasks.dll

Do you have any idea how to resolve it ?

2

Hello,

  • What operating system are you using?
  • Did you make any changes to source, or are you attempting to build it for the first time?
  • Does this only occur with 4.11 Preview source builds?
  • Are you able to build C++ projects in a non-source version of the engine?
3

Hello,

I am marking this topic as resolved for tracking purposes, as we have not heard from you in a few days. If this issue persists, feel free to respond to this thread. For any new issues, please create a new Answerhub topic.

Have a great day

4

I can confirm this issue on current master and promoted branches. It is directly related to breaking changes introduced in VS2015 Update 1 that are explained here Visual C++ What's New 2003 through 2015 | Microsoft Docs (#pragma optimize() extends past end of header file). The VS2013 compilation is unaffected and works without problems.

5

Thank You, I confirm that problem is solved (verified in UE4.11p7) :slight_smile:

Have a great day

6

We’re hitting the same thing, but only in one configuration; we clearly grabbed our latest drop a bit too early.

What was the specific fix for this? Was it a change to the core macros and/or compilation settings, or were there some engine headers that were leaking optimize settings which have now been cleaned up?

Cheers,

7

Having this issue myself now as well. 4.12.4. It was fine when I was in “Development Editor”,but switching to “DebugGame Editor” now I am running into this issue.

8

Do you happen to be using Visual Studio 2015 Update 3? There was a fix for Update 3-related issues pushed into 4.12.5.

Could you provided the error messages you are seeing so I can take a closer look?

9

I just checked and we are actually using Update 1. Should I get systems to install a specific update?

10

Hi Sean,

EDIT: I was actually wrong. We are already using 4.12.5

Updated to Update 3 and still having this issue. We are currently on 4.12.4 and I don’t have the option in the short term of moving to 4.12.5. We are longer term (in the next few weeks) going to move to 4.13 but I have bugs I need to get fixed in our tools now on 4.12.4

Is there any information on what I can change in 4.12.4 to get this to compile? I really need proper debugging to track down a tricky bug.

The error is exactly as stated above: error C4426: optimization flags changed after including header, may be due to #pragma optimize()

Now interestingly the compiler is calling out one of OUR files with this error, but I assume it is simply a carry over from something we are including since we aren’t doing anything special in our files.