Re: [PATCH] Makefile: fix use of -j without an argument

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

Hi Matheus,

On 11/4/24 17:09, Matheus Tavares Bernardino wrote:
> Our Makefile massages the given make arguments to invoke ninja
> accordingly. One key difference is that ninja will parallelize by
> default, whereas make only does so with -j<n> or -j. The make man page
> says that "if the -j option is given without an argument, make will not
> limit the number of jobs that can run simultaneously". We use to support
> that by replacing -j with "" (empty string) when calling ninja, so that
> it would do its auto-parallelization based on the number of CPU cores.
> 
> This was accidentally broken at d1ce2cc95b (Makefile: preserve
> --jobserver-auth argument when calling ninja, 2024-04-02),
> causing `make -j` to fail:
> 
> $ make -j V=1
>    /usr/bin/ninja -v   -j -d keepdepfile all | cat
>    make  -C contrib/plugins/ V="1" TARGET_DIR="contrib/plugins/" all
>    ninja: fatal: invalid -j parameter
>    make: *** [Makefile:161: run-ninja] Error
> 
> Let's fix that and indent the touched code for better readability.
> 
> Signed-off-by: Matheus Tavares Bernardino <quic_mathbern@quicinc.com>
> ---
>   Makefile | 8 ++++++--
>   1 file changed, 6 insertions(+), 2 deletions(-)
> 
> diff --git a/Makefile b/Makefile
> index 183756018f..d299c14dab 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -142,8 +142,12 @@ MAKE.k = $(findstring k,$(firstword $(filter-out --%,$(MAKEFLAGS))))
>   MAKE.q = $(findstring q,$(firstword $(filter-out --%,$(MAKEFLAGS))))
>   MAKE.nq = $(if $(word 2, $(MAKE.n) $(MAKE.q)),nq)
>   NINJAFLAGS = $(if $V,-v) $(if $(MAKE.n), -n) $(if $(MAKE.k), -k0) \
> -        $(or $(filter -l% -j%, $(MAKEFLAGS)), $(if $(filter --jobserver-auth=%, $(MAKEFLAGS)),, -j1)) \
> -        -d keepdepfile
> +        $(if $(filter -j, $(MAKEFLAGS)) \
> +	     ,, \
> +	     $(or \
> +	          $(filter -l% -j%, $(MAKEFLAGS)), \
> +	          $(if $(filter --jobserver-auth=%, $(MAKEFLAGS)),, -j1)) \
> +        ) -d keepdepfile
>   ninja-cmd-goals = $(or $(MAKECMDGOALS), all)
>   ninja-cmd-goals += $(foreach g, $(MAKECMDGOALS), $(.ninja-goals.$g))
>   

Apparently Martin sent the same patch (although not as nicely
indented) and Paolo queued it:
https://lore.kernel.org/qemu-devel/20240402081738.1051560-1-martin@geanix.com/