Re: [PATCH 1/5] make: add use of $(realpath ) in top and main Rules.mk files

[Elliott Mitchell <ehem+xen@xxxxxxx>]

On Mon, Oct 26, 2026 at 10:01:59AM +0100, Jan Beulich wrote:
> On 19.10.2026 21:02, Elliott Mitchell wrote:
> > Date: Sat, 17 Oct 2026 12:25:36 -0700
> > 
> > Without this "/.." tend to accumulate in $(XEN_ROOT) and eventually
> > things start breaking.
> 
> "breaking" as in what exactly happening?

This is a scar from a project I was involved in several years back.  One
issue is dependencies are computed/compared as strings.  In particular
if multiple parent directory references are made one part of a project
might end up depending on:

foo/../bar/../baz

While another might end up depending on:

bar/../foo/../bar

If building is done in parallel you can end up with two processes
entering the same directory at the same time and colliding.

I imagine other problems/manifestations can occur.  I have not observed
any of these occuring with Xen's build, but this is something I tend to
preemptively address.  Strings including "/../" do occur in Xen's build
so there is some concern issues could occur in the future.

Certainly not urgent, but something which could become an issue.


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