HTML5 launch fails on cpp projects

Hi there,

I noticed that I had some building errors using HTML5 so I tested it on some clean new projects to narrow down the issue. Bottom line, only the Blueprint projects managed to be launched in the browser (Firefox Nightly 64Bit).

The steps for reproducing the error:

Start 4.12 → New Project → Blueprint → First Person (With Starter Content) → Launch Nightly(64bit) → Works!

Start 4.12 → New Project → C++ → First Person (With Starter Content) → Launch Nightly (64Bit) →

Hangs for a while at:

..
LogPlayLevel: UnrealBuildTool: INFO:root:Closure compiler (E:\Epic Games\4.12\Engine\Source\ThirdParty\HTML5\emsdk\emscripten\1.35.0\third_party\closure-compiler\compiler.jar) does not exist, check the paths in E:\Epic Games\4.12\Engine\Intermediate\Build\HTML5\.emscripten

then the Error appeares:

..
LogPlayLevel: BUILD FAILED
PackagingResults:Error: Error Launch failed! Unknown Error

Thanks!

Edit:
Full log

Edit2:
It works in 4.12.1

Hey Ionbordura,

This seems to be an issue with the following files:

LogPlayLevel: UnrealBuildTool:   File "E:\Epic Games\4.12\Engine\Source\ThirdParty\HTML5\emsdk\emscripten\1.35.0\emcc", line 1344, in <module>
LogPlayLevel: UnrealBuildTool:     final = shared.Building.emscripten(final, append_ext=False, extra_args=extra_args)
LogPlayLevel: UnrealBuildTool:   File "E:\Epic Games\4.12\Engine\Source\ThirdParty\HTML5\emsdk\emscripten\1.35.0\tools\shared.py", line 1565, in emscripten
LogPlayLevel: UnrealBuildTool:     call_emscripten(cmdline)
LogPlayLevel: UnrealBuildTool:   File "E:\Epic Games\4.12\Engine\Source\ThirdParty\HTML5\emsdk\emscripten\1.35.0\emscripten.py", line 1304, in _main
LogPlayLevel: UnrealBuildTool:     temp_files.run_and_clean(lambda: main(
LogPlayLevel: UnrealBuildTool:   File "E:\Epic Games\4.12\Engine\Source\ThirdParty\HTML5\emsdk\emscripten\1.35.0\tools\tempfiles.py", line 64, in run_and_clean
LogPlayLevel: UnrealBuildTool:     return func()
LogPlayLevel: UnrealBuildTool:   File "E:\Epic Games\4.12\Engine\Source\ThirdParty\HTML5\emsdk\emscripten\1.35.0\emscripten.py", line 1310, in <lambda>
LogPlayLevel: UnrealBuildTool:     DEBUG_CACHE=DEBUG_CACHE,
LogPlayLevel: UnrealBuildTool:   File "E:\Epic Games\4.12\Engine\Source\ThirdParty\HTML5\emsdk\emscripten\1.35.0\emscripten.py", line 1208, in main
LogPlayLevel: UnrealBuildTool:     temp_files=temp_files, DEBUG=DEBUG, DEBUG_CACHE=DEBUG_CACHE)
LogPlayLevel: UnrealBuildTool:   File "E:\Epic Games\4.12\Engine\Source\ThirdParty\HTML5\emsdk\emscripten\1.35.0\emscripten.py", line 1168, in emscript
LogPlayLevel: UnrealBuildTool:     outfile.write(funcs_js[i])
LogPlayLevel: UnrealBuildTool: IOError: [Errno 0] Error
LogPlayLevel: UnrealBuildTool: ERROR: UBT ERROR: Failed to produce item: E:\Projects\FirstPersonCpp\Binaries\HTML5\FirstPersonCpp.js

I did however go ahead and launch a C++ First Person project with starter content to FireFox Nightly 64bit without any trouble. I’m currently on 4.12.1. Which version of the engine are you on? Is it source or binary?

Thanks!

Hi, I used 4.12 binary, however after upgrading to 4.12.1 it managed to build. Not sure if it was a bug in 4.12 or not though, I will mark this as solved. Cheers!