[for-2.0] configure: use do_cc when checking for -fstack-protector support

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.

How about checking both do_cc and compile_prog here?




> ---
> This should be a pretty safe change and it prevents clang/MacOSX
> builds from spewing a warning on every C file compilation, so I'd
> like to get it into 2.0.
> 
>  configure | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/configure b/configure
> index eb0e7bb..c85475f 100755
> --- a/configure
> +++ b/configure
> @@ -1448,7 +1448,7 @@ done
>  if test "$stack_protector" != "no" ; then
>    gcc_flags="-fstack-protector-strong -fstack-protector-all"
>    for flag in $gcc_flags; do
> -    if compile_prog "-Werror $flag" "" ; then
> +    if do_cc $QEMU_CFLAGS -Werror $flag -c -o $TMPO $TMPC ; then
>        QEMU_CFLAGS="$QEMU_CFLAGS $flag"
>        LIBTOOLFLAGS="$LIBTOOLFLAGS -Wc,$flag"
>        break
> -- 
> 1.8.5.4
>

Long term we might want this:

But I'm not sure it's a good idea to make this change
so late.

-->

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>

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.

> 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

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

On 10 April 2014 18:51, Michael S. Tsirkin <mst@redhat.com> wrote:
> Reviewed-by: Michael S. Tsirkin <mst@redhat.com>

Thanks; patch applied to master.

-- PMM