mv error building LilyPond tests, maybe MAX_PATH related

[Marco Atzeri]

On 08/03/2025 06:10, Saul Tobin via Cygwin wrote:
> Hello,
> 
> I've encountered a kind of bizarre error when trying to build GNU LilyPond
> regression tests on Cygwin 3.5.7-1 on Windows 11. For one and only one
> folder, `mv` fails with `mv: cannot move './out-test' to
> './out-test-baseline': Permission denied`. The distinguishing feature of
> the failing folder seems to be that it contains its own subfolder with a
> copy of all the regtest files, some of which have rather long names. When I
> remove this subfolder, the error goes away. The error also goes away if I
> execute the rename in a way that forces a physical move of the files.
> 
> Based on this, it appears to me that when an in-place rename is performed
> by `mv`, it calls into a Win32 API that enforces the 260 character
> MAX_PATH. I can see in the trace that the error is occurring within a Win32
> call stack for resolving absolute path names, though the error code isn't
> specific enough to distinguish the precise reason for the failure.
> 
> I tried enabling LongPathsEnabled in the registry, but I get the same `mv`
> error after doing so and rebooting.
> 
> I reported this as a LilyPond bug with some further detail here
> https://gitlab.com/lilypond/lilypond/-/issues/6799, but the initial
> sentiment seems to be that this is an upstream issue.
> 
> In some respect this doesn't seem like a specifically Cygwin issue, since I
> encountered the same error in the same spot on WSL2 if the build tree was
> on the Windows filesystem. But I'm guessing if anybody knows how to answer
> this, it's probably folks on this list.
> 
> Any ideas what's going on here and how I might get it working? Is this a
> known type of issue? Is it a bug? If it's a bug, what is it a bug in?
> 
> Right now, LilyPond's developer documentation basically just says not to
> bother trying to compile on Windows. It would be REALLY nice to change
> that, and this is the only blocking issue from recommending Cygwin as a
> viable compilation environment for LilyPond development.
> 
> Thanks in advance for your help,
> 
> Saul
> 

Hi Saul,
it is a know issue by long but I never did an analysis like yours to 
identify the root cause.

I just skip to run the full tests when uploading the lilypond pkg

When I have extra time I will look again

Regards
Marco