# Visual Studio bulid errors after using GenerateProjectFiles.bat

**URL:** <https://forums.unrealengine.com/t/visual-studio-bulid-errors-after-using-generateprojectfiles-bat/416261>\
**Category:** Pipeline & Plugins\
**Tags:** generateprojectfiles, build-error, unreal-engine, Visual-Studio, question\
**Created:** [February 2, 2018, 8:24pm UTC](https://forums.unrealengine.com/t/visual-studio-bulid-errors-after-using-generateprojectfiles-bat/416261 "2018-02-02T20:24:51Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![anonymous\_user\_b58cf9e8](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/8/5/28502927f1d97ba1051b3b47ccfe17233bf41ef0.png) [@anonymous\_user\_b58cf9e8](https://forums.unrealengine.com/u/anonymous_user_b58cf9e8)\
**Post date:** [February 2, 2018, 8:24pm UTC](https://forums.unrealengine.com/t/visual-studio-bulid-errors-after-using-generateprojectfiles-bat/416261/1 "2018-02-02T20:24:51Z")

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After generating a project .sln file using GenerateProjectFiles.bat compilation of several engine modules fails in VisualStudio with the of the following error:

```
EXEC : error : UnrealBuildTool Exception: A conflicting instance of UnrealBuildTool is already running at this location: C:\\unreal\UnrealEngine\Engine\Binaries\DotNET\UnrealBuildTool.exe. A process manager may be used to determine the conflicting process and what tool may have launched it.

```

This appears to affect the following modules:  
TestPAL, UnrealFileServer, UnrealLightMass, UnrealCEFSubProcess, UnrealPak, BootstrapPackagedGame, UnrealHeaderTool, BuildPatchTool, CrashReportClient, SlateViewer, SymbolDebugger, UnrealVersionSelector, UnrealWatchdog, UnrealFrontend, BlankProgram, ShaderCacheTool, UnrealVersionSelector, MiniDumpDiagnostics,

A .sln generated by creating a new C++ project from the UE4Editor UI does not appear to have this issue. Likewise I am able to build the project itself either by building it exclusively in Visual Studio, building manually using Build.bat or by omitting the ‘-Engine’ flag from the GenerateProjectFiles.bat command

Command used to generate project project files:

```
[Path-To-Engine]/Build/BatchFiles/GenerateProjectFiles.bat [Path-To-Project]/MyProject.uproject -Game -Engine -2015

```

This seems to have started occurring since upgrading to 4.18.3. I am using the same process to generate project files that I have for previous versions of the engine/project. Please let me know if I am doing something wrong here.

Thank You

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<div class="post-metadata">

**Author:** ![Steeve\_Kilhoffer](https://d1ap1mz92jnks1.cloudfront.net/user_avatar/forums.unrealengine.com/steeve_kilhoffer/32/464715_2.png) [@Steeve\_Kilhoffer](https://forums.unrealengine.com/u/Steeve_Kilhoffer)\
**Post date:** [September 3, 2018, 10:30am UTC](https://forums.unrealengine.com/t/visual-studio-bulid-errors-after-using-generateprojectfiles-bat/416261/2 "2018-09-03T10:30:37Z")

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Hi Clayton! Did you figure out what was happening?

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**Author:** ![Apuzinio](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/8/5/28502927f1d97ba1051b3b47ccfe17233bf41ef0.png) [@Apuzinio](https://forums.unrealengine.com/u/Apuzinio)\
**Post date:** [February 20, 2019, 5:32am UTC](https://forums.unrealengine.com/t/visual-studio-bulid-errors-after-using-generateprojectfiles-bat/416261/3 "2019-02-20T05:32:38Z")

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This issue is triggered by running multiple build processes. Visual Studio 2017 number of build threads can be set from:  
Tools → Options → Projects and Solutions → Build and Run → maximum number of parallel project builds

Setting it to 1 allowed my solution to build correctly. I would suggest setting the number of build processes back to default (8 in my case) after building the engine since it could have significant impact on Visual Studio performance.

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<div class="post-metadata">

**Author:** ![anonymous\_user\_8fe8ffc6](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/8/5/28502927f1d97ba1051b3b47ccfe17233bf41ef0.png) [@anonymous\_user\_8fe8ffc6](https://forums.unrealengine.com/u/anonymous_user_8fe8ffc6)\
**Post date:** [February 7, 2021, 4:37pm UTC](https://forums.unrealengine.com/t/visual-studio-bulid-errors-after-using-generateprojectfiles-bat/416261/4 "2021-02-07T16:37:21Z")

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Worked for me! (same trouble with UE 4.18 from git) It’s kind of a bummer since I’m seating on a 12 core CPU… The good news is although projects won’t run in parallel the .obj are still processed simultaneously, I’m using 100% cores except on linking phase.