Pass user defines for Barebox build

[Ahmad Fatoum]

Hello Lior,

On 27.11.23 08:02, Lior Weintraub wrote:
> Hi guys,
> 
> Is there a formal way to pass user compilation flags into Barebox build?

There isn't. Both barebox and Linux have been broken in the past by distros
setting CFLAGS that force hardening options that require kernel/libc cooperation,
which didn't apply to barebox. For that reason, the variables were prefixed
with KBUILD_ and a way to inject variables into the build of barebox itself
(i.e. not host tools) is intentionally not provided.

What options do you want to inject?

> I couldn't find one so I just patched the main Makefile 
> diff --git a/Makefile b/Makefile
> index 471bbc2679..febc94b7f3 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -443,7 +443,7 @@ KBUILD_CPPFLAGS        := -D__KERNEL__ -D__BAREBOX__ $(LINUXINCLUDE) -fno-builti
>  KBUILD_CFLAGS   := -Wall -Wundef -Werror=strict-prototypes -Wno-trigraphs \
>                    -fno-strict-aliasing -fno-common -fshort-wchar \
>                     -Werror=implicit-function-declaration -Werror=implicit-int \
> -                   -Os -pipe -Wmissing-prototypes -std=gnu89
> +                   -Os -pipe -Wmissing-prototypes -std=gnu89 $(BAREBOX_USER_CFLAGS)

USER is an unfortunate name, because there's already KBUILD_USERCFLAGS
and that user is short for userspace and not the user, who is building
barebox.

Cheers,
Ahmad

>  KBUILD_AFLAGS          := -D__ASSEMBLY__
>  KBUILD_AFLAGS_KERNEL :=
>  KBUILD_CFLAGS_KERNEL :=
> 
> This patch allowed me to set BAREBOX_CFLAGS environment when calling make.
> 
> Thanks,                         
> Lior.
> 
> 
> 

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