Re: [PATCH V7 1/4] rust: Fix a race condition in Makefile

[Mukesh Kumar Chaurasiya]

On Sun, Mar 29, 2026 at 07:26:55PM +0100, Gary Guo wrote:
> On Sun Mar 29, 2026 at 6:25 PM BST, Miguel Ojeda wrote:
> > On Sun, Mar 29, 2026 at 6:03 PM Mukesh Kumar Chaurasiya (IBM)
> > <mkchauras@xxxxxxxxx> wrote:
> >>
> >> When compiling with -j1 flag in powerpc, the libproc_macro finds the
> >> libcore.rmeta both in toolchain and local rust directory. libproc_macro
> >> should use the toolchain provided libcore.rmeta.
> >
> > By toolchain, do you mean the sysroot one or something else?
> >
> > We should make it such that `rustc` does not try to use them to begin
> > with, e.g. we added `--sysroot=/dev/null` to prevent that in the past,
> > please see:
> >
> >   71479eee9da8 ("rust: Suppress searching builtin sysroot")
> >
> > In other words, we should try to avoid adding dependencies (even if
> > order-only) to workaround the issue, but instead we should get rid of
> > the root issue.
> >
> > Otherwise, after a build, if we rebuild only one of them, wouldn't it
> > find again both? i.e. this is not really a "race condition".
> >
> > From the original message, I see this was happening when building the
> > host libraries, because the targets happen to match, i.e. you are
> > doing a native build on powerpc, right?
> >
> > Perhaps we could put the host `.rmeta`s separately, or something like that.
> 
> Yeah, we can either remove `-L$(objtree)/$(obj)` and specify `--extern
> dep=path-to-dep`, or we can store host libraries to something like
> `$(objtree)/$(obj)/host` and use that instead.
> 
Oh now i understood what Miguel was trying to say. Thanks for the
explanation. 
> The latter should be an easier fix. Also, I can see that we're already having
> `-L$(objtree)/$(obj)/test`.
> 
I'll try this.

Regards,
Mukesh
> Best,
> Gary
>