Re: [Qemu-devel] [PATCH] configure: make it possible to disable IASL

["Michael S. Tsirkin" <mst@redhat.com>]

On Sun, Nov 24, 2013 at 09:58:34PM +0100, Stefan Weil wrote:
> Am 24.11.2013 17:48, schrieb Michael S. Tsirkin:
> > On Sun, Nov 24, 2013 at 05:39:58PM +0200, Michael S. Tsirkin wrote:
> >> On Sun, Nov 24, 2013 at 02:54:51PM +0100, Stefan Weil wrote:
> >>> Am 24.11.2013 14:42, schrieb Michael S. Tsirkin:
> >>>> On Sun, Nov 24, 2013 at 03:04:04PM +0200, Marcel Apfelbaum wrote:
> >>>>> On Sun, 2013-11-24 at 11:52 +0200, Michael S. Tsirkin wrote:
> >>>>>> Useful for platforms with a broken IASL.
> >>>>>>
> >>>>>> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
> >>>>>> ---
> >>>>>>  configure | 3 ++-
> >>>>>>  1 file changed, 2 insertions(+), 1 deletion(-)
> >>>>>>
> >>>>>> diff --git a/configure b/configure
> >>>>>> index 0592ba7..d0a0abe 100755
> >>>>>> --- a/configure
> >>>>>> +++ b/configure
> >>>>>> @@ -1080,6 +1080,7 @@ echo "  --source-path=PATH       path of source code [$source_path]"
> >>>>>>  echo "  --cross-prefix=PREFIX    use PREFIX for compile tools [$cross_prefix]"
> >>>>>>  echo "  --cc=CC                  use C compiler CC [$cc]"
> >>>>>>  echo "  --iasl=IASL              use ACPI compiler IASL [$iasl]"
> >>>>>> +echo "                           iasl='' (empty string) disables ACPI compiler"
> >>>>>>  echo "  --host-cc=CC             use C compiler CC [$host_cc] for code run at"
> >>>>>>  echo "                           build time"
> >>>>>>  echo "  --cxx=CXX                use C++ compiler CXX [$cxx]"
> >>>>>> @@ -4269,7 +4270,7 @@ else
> >>>>>>  fi
> >>>>>>  echo "PYTHON=$python" >> $config_host_mak
> >>>>>>  echo "CC=$cc" >> $config_host_mak
> >>>>>> -if $iasl -h > /dev/null 2>&1; then
> >>>>>> +if test "$iasl" && $iasl -h > /dev/null 2>&1; then
> >>>>>>    echo "IASL=$iasl" >> $config_host_mak
> >>>>>>  fi
> >>>>>>  echo "CC_I386=$cc_i386" >> $config_host_mak
> >>>>> I tried to disable iasl without this patch and it worked for me...
> >>>>> I used:
> >>>>>     - [Qemu-devel] [PATCH] configure: make --iasl option actually work
> >>>>>     - ./configure --iasl="" (or --iasl=)
> >>>>> and it worked (no sign of IASL in config-host.mak)
> >>>>>
> >>>>> I think this is because the prev test "$iasl -h > /dev/null 2>&1"
> >>>>> fails of course.
> >>>> By luck, yes.
> >>>>
> >>>> So this is just a documentation patch: cleaner to document the
> >>>> interface explicitly.
> >>>> I'll make this clearer in the commit log.
> >>>>
> >>> --iasl=false works without further modifications (because test "false
> >>> -h" works and returns false). It also looks more natural than --iasl=.
> >>>
> >>> Cheers, Stefan
> >> It seems that some people try --iasl= as the more natural way
> >> to do this. It's not documented that a failing iasl will
> >> cause a fall-back and I'd rather document an explicit option
> >> than making it fail.
> > I'm also curious why would you say =false is natural:
> > it's a string option not a boolean one.
> >
> 
> 'false' is a string here, namely the name of the executable which is
> normally found at /bin/false.
> It takes any number of parameters and always returns 1 (which is boolean
> false
> in shell conventions).
> 
> You could also write --iasl=/bin/false.
> 
> I suggest this kind of patch:
> 
>  echo "  --iasl=IASL              use ACPI compiler IASL [$iasl]"
> +echo "                           iasl=false disables the ACPI compiler"

It's still not a natural interface.

It works by chance because we run iasl and test the return code,
but we don't have to.
For example, a reasonable implementation might produce
an error if the user-specified iasl fails, breaking this hack.

Interfaces should not follow implementation.
If you don't want iasl a reasonable syntax is '' or
--disable-iasl.

>  echo "  --host-cc=CC             use C compiler CC [$host_cc] for code run at"
> 
> 
> Stefan