Re: [PATCH] Kbuild: add RUSTC_BOOTSTRAP to rustc-option

[Masahiro Yamada]

On Wed, Oct 9, 2024 at 5:06 AM Miguel Ojeda
<miguel.ojeda.sandonis@xxxxxxxxx> wrote:
>
> On Tue, Oct 8, 2024 at 8:45 PM Masahiro Yamada <masahiroy@xxxxxxxxxx> wrote:
> >
> > Really?
> >
> > $(shell ...) inherits env variables in my understanding.
>
> I mean the Make-exported variables (not the external environment),
> i.e. `RUSTC_BOOTSTRAP=1` that we export in the main `Makefile`. Those
> are not exported into the `shell` function.
>
> However, it turns out this changes in GNU Make 4.4 in commit
> 98da874c4303 ("[SV 10593] Export variables to $(shell ...) commands"):
>
>     * WARNING: Backward-incompatibility!
>       Previously makefile variables marked as export were not exported
> to commands
>       started by the $(shell ...) function.  Now, all exported variables are
>       exported to $(shell ...).  If this leads to recursion during
> expansion, then
>       for backward-compatibility the value from the original
> environment is used.
>       To detect this change search for 'shell-export' in the .FEATURES variable.
>
> And indeed:
>
>     export A := .PHONY: a
>     $(shell echo $$A)
>     a: ; @echo exported
>
> Gives:
>
>     $ make-4.3
>     make: 'a' is up to date.
>
>     $ make-4.4.1
>     exported


OK, I reached the same understanding now.




--
Best Regards
Masahiro Yamada