Re: [PATCH] build: further refine build.ninja rules

["Philippe Mathieu-Daudé" <philmd@linaro.org>]

On 8/6/23 15:43, Paolo Bonzini wrote:
> In commit b0fcc6fc7fc1 ("build: rebuild build.ninja using
> "meson setup --reconfigure"", 2023-05-19) I changed the build.ninja
> rule in the Makefile to use "meson setup" so that the Makefile would
> pick up a changed path to the meson binary.
> 
> However, there was a reason why build.ninja was rebuilt using $(NINJA)
> itself.  Namely, ninja has its own cache of file modification times,
> and if it does not know about the modification that was done outside
> its control, it will *also* try to regenerate build.ninja.  This can be
> simply by running "make" on a fresh tree immediately after "configure";
> that will trigger an unnecessary meson run.
> 
> So, apply a refinement to the rule in order to cover both cases:
> 
> - track the meson binary that was used (and that is embedded in
>    build.ninja's reconfigure rules); to do this, write build.ninja.stamp
>    right after executing meson successfully
> 
> - if it changed, force usage of "$(MESON) setup --reconfigure" to
>    update the path in the reconfigure rule
> 
> - if it didn't change, use "$(NINJA) build.ninja" just like before
>    commit b0fcc6fc7fc1.
> 
> Reported-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
> ---
>   Makefile  | 17 +++++++++++++----
>   configure |  1 +
>   2 files changed, 14 insertions(+), 4 deletions(-)

Tested-by: Philippe Mathieu-Daudé <philmd@linaro.org>