Re: [PATCH 1/3] compat/mingw: share file handles created via `CreateFileW()`

> On Wed, Oct 23, 2024 at 05:04:58PM +0200, Patrick Steinhardt wrote:
> > Unless told otherwise, Windows will keep other processes from reading,
> > writing and deleting files when one has an open handle that was created
> > via `CreateFileW()`. This behaviour can be altered via `FILE_SHARE_*`
> > flags such that other processes _can_ read and/or modify such a file.
> > This sharing mechanism is quite important in the context of Git, as we
> > assume POSIX semantics all over the place.
> >
> > There are two calls where we don't set up those flags though:
> >
> >   - We don't set `FILE_SHARE_DELETE` when creating a file for appending
> >     via `mingw_open_append()`. This makes it impossible to delete the
> >     file from another process or to replace it via an atomic rename.
> >
> >   - When opening a file such that we can change its access/modification
> >     times. This makes it impossible to perform any kind of operation
> >     on this file at all from another process. While we only open the
> >     file for a short amount of time to update its timestamps, this still
> >     opens us up for a race condition with another process.
> >
> > Adapt both of these callsites to pass all three sharing flags.
>
> Interesting, and especially so noting that we *do* call CreateFileW()
> with the FILE_SHARE_DELETE flag in other functions like create_watch(),
> mingw_open_existing(), mingw_getcwd(), etc.