Re: [PATCH] build: disable fcf-protection on -march=486 -m16

[Thomas Huth <thuth@redhat.com>]

On 23/03/2022 10.07, christian.ehrhardt@canonical.com wrote:
> From: Christian Ehrhardt <christian.ehrhardt@canonical.com>
> 
> Some of the roms build with -march=i486 -m16 which is incompatible
> with -fcf-protection. That in turn is can be set by default, for
> example in Ubuntu [1].
> That causes:
>   cc1: error: ‘-fcf-protection’ is not compatible with this target
> 
> This won't work on -march=i486 -m16 and no matter if set or not we can
> override it to "none" if the option is known to the compiler to be
> able to build reliably.
> 
> Fixes: https://gitlab.com/qemu-project/qemu/-/issues/889
> 
> [1]: https://wiki.ubuntu.com/ToolChain/CompilerFlags#A-fcf-protection
> 
> Signed-off-by: Christian Ehrhardt <christian.ehrhardt@canonical.com>
> ---
>   pc-bios/optionrom/Makefile | 4 ++++
>   1 file changed, 4 insertions(+)
> 
> diff --git a/pc-bios/optionrom/Makefile b/pc-bios/optionrom/Makefile
> index 5d55d25acc..f1ef898073 100644
> --- a/pc-bios/optionrom/Makefile
> +++ b/pc-bios/optionrom/Makefile
> @@ -14,6 +14,10 @@ cc-option = $(if $(shell $(CC) $1 -c -o /dev/null -xc /dev/null >/dev/null 2>&1
>   
>   override CFLAGS += -march=i486 -Wall
>   
> +# If -fcf-protection is enabled in flags or compiler defaults that will
> +# conflict with -march=i486
> +override CFLAGS += $(call cc-option, -fcf-protection=none)
> +
>   # Flags for dependency generation
>   override CPPFLAGS += -MMD -MP -MT $@ -MF $(@D)/$(*F).d
>   

Reviewed-by: Thomas Huth <thuth@redhat.com>