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Date: Thu, 10 Apr 2014 20:51:40 +0300
From: "Michael S. Tsirkin" <mst@redhat.com>
Message-ID: <20140410175140.GB28144@redhat.com>
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Subject: Re: [Qemu-devel] [PATCH for-2.0] configure: use do_cc when checking
 for -fstack-protector support
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To: Peter Maydell <peter.maydell@linaro.org>
Cc: Paolo Bonzini <pbonzini@redhat.com>, Andreas =?iso-8859-1?Q?F=E4rber?= <andreas.faerber@web.de>, Patch Tracking <patches@linaro.org>, Steven Noonan <steven@uplinklabs.net>, QEMU Developers <qemu-devel@nongnu.org>

On Thu, Apr 10, 2014 at 05:37:31PM +0100, Peter Maydell wrote:
> On 10 April 2014 17:31, Michael S. Tsirkin <mst@redhat.com> wrote:
> > On Wed, Apr 09, 2014 at 12:04:47PM +0100, Peter Maydell wrote:
> >> MacOSX clang silently swallows unrecognized -f options when doing a link
> >> with '-framework' also on the command line, so to detect support for
> >> the various -fstack-protector options we must do a plain .c to .o compile,
> >> not a complete compile-and-link.
> >>
> >> Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
> >
> > Hmm it worries me a bit that we aren't passing it to linker:
> > might break some builds in case compiler has a working
> > protector but linker doesn't.
> 
> Given we both compile and link (in configure) with the
> same $compiler binary, this seems vanishingly unlikely.


True - I really meant libtool but we don't test it ATM
so we can leave that for another day.

OK fair enough:

Reviewed-by: Michael S. Tsirkin <mst@redhat.com>


> > configure: check -c each time we run compiler
> >
> > Some warnings/errors only surface if you run compiler
> > without a linker. Run both on each test.
> >
> > Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
> >
> >
> > diff --git a/configure b/configure
> > index eb0e7bb..8adc72b 100755
> > --- a/configure
> > +++ b/configure
> > @@ -102,6 +102,7 @@ compile_object() {
> >  compile_prog() {
> >    local_cflags="$1"
> >    local_ldflags="$2"
> > +  do_cc $QEMU_CFLAGS -c $local_cflags -o $TMPO $TMPC
> >    do_cc $QEMU_CFLAGS $local_cflags -o $TMPE $TMPC $LDFLAGS $local_ldflags
> >  }
> >
> 
> That's a lot of extra compiles and configure isn't
> exactly a speed demon as it is...
> 
> thanks
> -- PMM