From: Patrick Steinhardt <ps@pks.im>
Date: Fri, 10 Oct 2025 05:36:45 GMT
Subject: Re: [PATCH] refs: forbid clang to complain about unreachable code
Message-ID: <aOibbUqe-gfal6sd@pks.im>
In-Reply-To: <xmqqzf9zddia.fsf@gitster.g>

On Thu, Oct 09, 2025 at 01:30:21PM -0700, Junio C Hamano wrote:
> "Johannes Schindelin via GitGitGadget" <gitgitgadget@gmail.com>
> writes:
> 
> > From: Johannes Schindelin <johannes.schindelin@gmx.de>
> >
> > When `NO_SYMLINK_HEAD` is defined, `create_ref_symlink()` is hard-coded
> > as `(-1)`, and as a consequence the condition `!create_ref_symlink()`
> > always evaluates to false, rendering any code guarded by that condition
> > unreachable.
> >
> > Therefore, clang is _technically_ correct when it complains about
> > unreachable code. It does completely miss the fact that this is okay
> > because on _other_ platforms, where `NO_SYMLINK_HEAD` is not defined,
> > the code isn't unreachable at all.
> >
> > Let's use the same trick as in 82e79c63642c (git-compat-util: add
> > NOT_CONSTANT macro and use it in atfork_prepare(), 2025-03-17) to
> > appease clang while at the same time keeping the `-Wunreachable` flag
> > to potentially find _actually_ unreachable code.
> >
> > Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
> > ---
> >     refs: forbid clang to complain about unreachable code
> >     
> >     Just upstreamin'
> 
> It may not be a bad idea to deprecate core.preferSymlinkRefs now and
> remove it at Git 3.0 boundary.  Some platforms may not be able to do
> symbolic links and use it to represent HEAD, but everybody should be
> able to create a small text file with a single line.
> 
> But until then, this is a very reasonable thing to do.

Agreed. I don't see any reason why anyone would like to use symbolic
refs for this. The reading side for such symrefs may continue to exist
for a while. But the writing side can go away.

Patrick