Re: [Xen-devel] [XEN PATCH v2 2/6] xen: Have Kconfig check $(CC)'s version

[Anthony PERARD <anthony.perard@xxxxxxxxxx>]

On Fri, Jan 03, 2020 at 05:42:18PM +0100, Jan Beulich wrote:
> On 17.12.2019 11:58, Anthony PERARD wrote:
> > --- a/xen/Kconfig
> > +++ b/xen/Kconfig
> > @@ -4,9 +4,26 @@
> >  #
> >  mainmenu "Xen/$(SRCARCH) $(XEN_FULLVERSION) Configuration"
> >  
> > +source "scripts/Kconfig.include"
> > +
> >  config BROKEN
> >     bool
> >  
> > +config CC_IS_GCC
> > +   def_bool $(success,$(CC) --version | head -n 1 | grep -q gcc)
> > +
> > +config GCC_VERSION
> > +   int
> > +   default $(shell,$(BASEDIR)/scripts/gcc-version.sh $(CC)) if CC_IS_GCC
> > +   default 0
> 
> Why "if" and a 2nd "default" line here but ...
> 
> > +config CC_IS_CLANG
> > +   def_bool $(success,$(CC) --version | head -n 1 | grep -q clang)
> > +
> > +config CLANG_VERSION
> > +   int
> > +   default $(shell,$(BASEDIR)/scripts/clang-version.sh $(CC))
> 
> ... just a single, unconditional one here?

clang-version.sh returns 0 when CC isn't clang, but gcc-version.sh
doesn't check if CC is gcc, and returns a bogus values instead.

e.g.:

$ ./clang-version.sh clang
90000
$ ./gcc-version.sh clang
40201

> Wouldn't both better
> have a "depends on CC_IS_*" line instead? This would then also
> result (afaict) in no CONFIG_CLANG_VERSION in .config if building
> with gcc (and vice versa), instead of a bogus CONFIG_CLANG_VERSION=0.

It sounds attracting to remove variables from .config, but it is equally
attracting to always have a variable set. It can be used
unconditionally when always set (without risking invalid syntax for
example).

Thanks,

-- 
Anthony PERARD

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