Re: [Minios-devel] [UNIKRAFT PATCH 5/9] build: Add a makefile rule to check valid gcc version

[Simon Kuenzer <simon.kuenzer@xxxxxxxxx>]

On 15.03.2018 04:39, Wei Chen wrote:
> Different GCC versions support different march, mcpu and mtune list.
> In order to avoid users to select unsupported optimization processor
> for the GCC they used. We add this check_valid_gcc_version rule to
> check GCC version and provide the minimum version for user selected
> processor.
>
> Signed-off-by: Wei Chen <Wei.Chen@xxxxxxx>
> ---
>   Makefile                     | 4 ++++
>   support/build/Makefile.rules | 8 ++++++++
>   2 files changed, 12 insertions(+)
>
> diff --git a/Makefile b/Makefile
> index 49e5070..997a359 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -426,6 +426,10 @@ LIFTOFF            := liftoff -e -s
>   override ARFLAGS:= rcs
>   CC_VERSION    := $(shell $(CC) --version | \
>                    sed -n -r 's/^.* ([0-9]*)\.([0-9]*)\.([0-9]*)[ ]*.*/\1.\2/p')
> +# Retrieve GCC major and minor number from CC_VERSION. They would be used
> +# to select correct optimization parameters for target CPUs.
> +CC_VER_MAJOR   := $(word 1,$(subst ., ,$(CC_VERSION)))
> +CC_VER_MINOR   := $(word 2,$(subst ., ,$(CC_VERSION)))
>   
>   ASFLAGS		+= -DCC_VERSION=$(CC_VERSION)
>   CFLAGS                += -DCC_VERSION=$(CC_VERSION)
> diff --git a/support/build/Makefile.rules b/support/build/Makefile.rules
> index e4ac264..e51f902 100644
> --- a/support/build/Makefile.rules
> +++ b/support/build/Makefile.rules
> @@ -29,6 +29,14 @@ lc = $(subst A,a,$(subst B,b,$(subst C,c,$(subst D,d,$(subst 
> E,e,$(subst F,f,$(s
>   # upper case
>   uc = $(subst a,A,$(subst b,B,$(subst c,C,$(subst d,D,$(subst e,E,$(subst 
> f,F,$(subst g,G,$(subst h,H,$(subst i,I,$(subst j,J,$(subst k,K,$(subst 
> l,L,$(subst m,M,$(subst n,N,$(subst o,O,$(subst p,P,$(subst q,Q,$(subst 
> r,R,$(subst s,S,$(subst t,T,$(subst u,U,$(subst v,V,$(subst w,W,$(subst 
> x,X,$(subst y,Y,$(subst z,Z,$(1)))))))))))))))))))))))))))
>   
> +# check whether the GCC meets the minimum version requirement
> +# $(1): The minimum GCC major number
> +# $(2): The minimum GCC minor number
> +# $(3): The optimization target CPU
> +define check_valid_gcc_version =
> +$(if $(shell test $(CC_VER_MAJOR) -gt $(1) -o '(' $(CC_VER_MAJOR) -eq $(1) -a 
> $(CC_VER_MINOR) -ge $(2) ')' && echo y),,\
> +     $(error Optimization for $(3) requires GCC version >= $(1).$(2)))
> +endef
Hum, I think this could be useful to a lot of other places in Unikraft.
But for this we should do a split. One definition should just do the 
test so that the result could be used for if statements.
I would call this one 'test_gcc_version'.

Yours should use 'test_gcc_version', and use $(error ) if GCC is too 
old. I would also the not talk about optimization in the error message. 
You could treat $(3) as optional argument or even remove it.
How about something like this:

Require GCC version >= $(1).$(2) (found $(CC_VER_MAJOR).$(CC_VER_MINOR))

>   
>   ################################################################################
>   #
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