Pathnames too long causing build failures

anonymous_user_d91c2fde · October 2, 2019, 9:31pm

When building the Unreal Engine 4.23 source, some of the pathnames are really, really, long, like:

\Engine\Plugins\Developer\Concert\ConcertSync\ConcertSyncServer\Intermediate\Build\Win64\UnrealDisasterRecoveryService\Development\ConcertSyncServer\UnrealDisasterRecoveryService-ConcertSyncServer.dll.response

this is 209 characters just by itself. If you have some prefix path in front of that, it can easily exceed 260 characters. On some people’s machines, this is causing a build failure.

3>LINK : fatal error LNK1104: cannot open file ‘E:\xxxxxxxxxSecondary\depot\xx\New\Dev\UnrealEngine\Engine\Plugins\Developer\Concert\ConcertSync\ConcertSyncServer\Intermediate\Build\Win64\UnrealDisasterRecoveryService\Development\ConcertSyncServer\UnrealDisasterRecoveryService-ConcertSyncServer.dll.response’

I am not sure under what circumstances 260 characters is still a limit in Windows. Does Epic recommend really short paths that prefix engine pathnames?

UE_FlavienP · October 3, 2019, 9:37am

You can extend the limit since 4.22 but it requires recent windows 10 version:
New: Support for long filenames (Experimental) We added support for long file paths for users with Windows 10 Anniversary Update! Historically, paths in windows have been limited to 260 characters, which can cause problems for projects with complex naming conventions and deep hierarchies of assets. The Windows 10 Anniversary Update adds support for much longer filenames, on the condition that the user and each application opt-in to it. To enable long file paths in Windows 10:

Ensure you’re running Windows 10 version 1607 or later
Enable support for long paths via the group policy setting or registry (see https://docs.microsoft.com/en-us/windows/desktop/FileIO/naming-a-file#maxpath))
In the Unreal Editor, check the “Enable Long Paths Support” in the experimental settings dialog.

Note: Support for long paths is not universal, and third party tools - even parts of the operating system, like Windows Explorer - may not support them correctly.

You can read about it in that post too, look for pf_breton answer.
https://forums.unrealengine.com/unreal-engine/unreal-studio/1659174-filename-length-issue-datasmith-revit

anonymous_user_d91c2fde · October 3, 2019, 3:55pm

Interesting, thx. In that pf_breton answer, I do not see the option described. In my build 1903 of Windows 10, I see “Enable Win32 long paths” one level up from where he describes under “Filesystem”.

But having people activate this individually seems doomed to failure. I guess for now we will just make sure our prefix paths are shorter than Epic’s so the problem doesn’t occur.