On Mon, Feb 19, 2018 at 10:01:49AM -0800, Linus Torvalds wrote:
> On Mon, Feb 19, 2018 at 9:44 AM, Linus Torvalds
> <torva...@linux-foundation.org> wrote:
> >
> > I do like your "success"/"stdout" more than "shell"/"shell-stdout",
> > because with that naming I don't get the feeling that one should
> > subsume the other.
>
> Hmm. Thinking about it some more, I really would prefer just "$(shell
> ...)" everywhere.
>
> But it would be nice if perhaps the error handling would match the
> context somehow.
>
> I'm wondering if this might tie into the whole quoting discussion in
> the other thread.
>
> Because the rule could be:
>
> (a) unquoted $(shell ) is a bool, and failing is ok (and turns into
> y/n depending on whether successful or failing)
>
> So
>
> config CC_IS_GCC
> bool
> default $(shell $CC --version | grep -q gcc)
>
> works automatically.
>
> (b) but with quoting, $(shell ) is a string, and failing is an error
>
> So
>
> config GCC_VERSION
> int
> default "$(shell-stdout $srctree/scripts/gcc-version.sh $CC
> | sed 's/^0*//')" if CC_IS_GCC
> default 0
>
> would need those quotes, and if the shell-script returns a failure,
> we'd _abort_.
>
> Which is actually what we want there.
>
> Hmm? Is that too nasty?
>
> Linus
One minor drawback would be slight kludginess if you want "n"/"y" put
into a string depending on the success of a command:
default "foo-$(shell cmd && echo y || echo n)"
As opposed to:
default "foo-$(success cmd)"
I don't know if that's significant enough to matter in practice.
Keeping it objective, I can't see any major downsides, though I'd really
prefer to just have $() do string interpolation within "". That keeps
the implementation trivial and makes the behavior and limitations
obvious once you know that n/m/y is just shorthand for "n"/"m"/"y".
Cheers,
Ulf
