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Re: [Qemu-devel] [PATCH for-2.0] configure: add option to disable -fstac
From: |
Noonan, Steven |
Subject: |
Re: [Qemu-devel] [PATCH for-2.0] configure: add option to disable -fstack-protector flags |
Date: |
Fri, 28 Mar 2014 18:04:37 +0000 |
User-agent: |
Microsoft-MacOutlook/14.3.9.131030 |
On 3/28/14, 10:51 AM, "Paolo Bonzini" <address@hidden> wrote:
>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.
Correct, -fstack-protector-all was too high impact. Sadly
-fstack-protector-strong seems to only exist in RedHat-provided compilers,
which I don't always use -- thus the new default this change provides
doesn't really help, so I'd need to just do 'configure
--disable-stack-protector' to avoid the performance penalty.