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Date: Fri, 28 Mar 2014 18:51:11 +0100
From: Paolo Bonzini <pbonzini@redhat.com>
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Subject: Re: [Qemu-devel] [PATCH for-2.0] configure: add option to disable
 -fstack-protector flags
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To: Laurent Desnogues <laurent.desnogues@gmail.com>
Cc: Steven Noonan <steven@uplinklabs.net>, Steven Noonan <snoonan@amazon.com>, "qemu-devel@nongnu.org" <qemu-devel@nongnu.org>, Anthony Liguori <aliguori@amazon.com>

Il 28/03/2014 18:41, Laurent Desnogues ha scritto:
>> > +  gcc_flags="-fstack-protector-strong -fstack-protector-all"
>> > +  for flag in $gcc_flags; do
>> > +    if compile_prog "-Werror $flag" "" ; then
>> > +      QEMU_CFLAGS="$QEMU_CFLAGS $flag"
>> > +      LIBTOOLFLAGS="$LIBTOOLFLAGS -Wc,$flag"
>> > +      break
>> > +    fi
>> > +  done
>> >  fi
> My understanding is that -fstack-protector, -fstack-protector-strong,
> and -fstack-protector-all are strictly ordered in terms of the number
> of functions that are checked, so you have changed the default
> behavior to check less functions for compilers that support
> -fstack-protector-strong.  Is that what you had in mind?

Yes.  -fstack-protector-all adds protection in places where it doesn't 
really matter, and that's why it has such a high cost.

Paolo