Re: [testsuite] PATCH: Add check_effective_target_pie

[Magnus Granberg <zorry@gentoo.org>]

måndag 12 januari 2015 12.11.17 skrev  H.J. Lu:
> On Mon, Jan 12, 2015 at 12:03 PM, Jeff Law <law@redhat.com> wrote:
> > On 01/12/15 12:59, H.J. Lu wrote:
> >> I don't know if -pg will work PIE on any targets.  For Linux/x86
> >> the choices of crt1.o are
> >> 
> >> %{!shared: %{pg|p|profile:gcrt1.o%s;pie:Scrt1.o%s;:crt1.o%s}}
> >> 
> >> -shared, -pg and -pie are mutually exclusive. Those crt1 files are
> >> only crt1 files provided by glibc.  You can't even try -pg -pie on
> >> Linux without changing glibc.
> > 
> > You're totally missing the point.  What I care about is *why*.
> > 
With -pg it use gcrt1.o object file and that file is not compile with -fPIC. 
When you build a shared lib on x86_64 all the objects files need to be buiit 
with -fPIC else you get a error like that one abow and it is the same problems 
when you build bin with -fPIE and linke with -pie.
Glibc do not provide one that is compile with -fPIC

> > Showing me spec file fragments is totally unhelpful.  What is the
> > technical
> > reason why pg and pie are mutually exclusive?
> 
> What kind of "technical" reason are you looking for?  glibc doesn't
> provide the right crt1 file for GCC to support this combination.  You
> can't define GNU_USER_TARGET_STARTFILE_SPEC to support
> -pg and -pie.
> 
> If you are asking "why" glibc doesn't provide one, my guess is no
> one has requested one before.