Re: [PATCH] kbuild: clang: remove crufty HOSTCFLAGS

[Segher Boessenkool <segher@kernel.crashing.org>]

On Sat, Sep 30, 2017 at 04:14:50PM -0700, Nick Desaulniers wrote:
> On Thu, Sep 28, 2017 at 07:52:35PM +0900, Masahiro Yamada wrote:
> > 2017-09-26 11:28 GMT+09:00 Nick Desaulniers <nick.desaulniers@gmail.com>:
> > >  HOSTCFLAGS   := -Wall -Wmissing-prototypes -Wstrict-prototypes -O2 \
> > > +               $(call hostcc-option,-fno-delete-null-pointer-checks) \
> > >                 -fomit-frame-pointer -std=gnu89 $(HOST_LFS_CFLAGS)
> > 
> > You call hostcc-option
> > before Kbuild.include is included around line 341.
> > 
> > So, $(call hostcc-option, ...) returns always an empty string here
> > whether the compiler supports the option or not.
> 
> So calling a yet-to-be defined variable results in an empty string
> rather than a loud failure?  Chalk that up there with language features
> no one ever asked for.  That kind of implicit conversion gets languages
> like JavaScript (with its loose type system, not that C is without its
> own implicit type conversions/promotions) in a lot of hot water.

make --warn-undefined-variables

(and it warns all over the place during a kernel build -- having undefined
variables expand to the empty string is a useful feature, too, not just a
trap for the unwary).


Segher