[PATCH] Fix pr80044, -static and -pie insanity, and pr81170

Alan Modra amodra@gmail.com
Mon Jul 17 12:33:00 GMT 2017


On Sat, Jul 15, 2017 at 06:32:40AM -0700, H.J. Lu wrote:
> On Thu, Jun 22, 2017 at 8:28 AM, Alan Modra <amodra@gmail.com> wrote:
> > PR80044 notes that -static and -pie together behave differently when
> > gcc is configured with --enable-default-pie as compared to configuring
> > without (or --disable-default-pie).  This patch removes that
> > difference.  In both cases you now will have -static completely
> > overriding -pie.
> >
> > Fixing this wasn't quite as simple as you'd expect, due to poor
> > separation of functionality.  PIE_SPEC didn't just mean that -pie was
> > on explicitly or by default, but also -r and -shared were *not* on.
> > Fortunately the three files touched by this patch are the only places
> > PIE_SPEC and NO_PIE_SPEC are used, so it isn't too hard to see that
> > the reason PIE_SPEC and NO_PIE_SPEC are not inverses is the use of
> > PIE_SPEC in LINK_PIE_SPEC.  So, move the inelegant symmetry breaking
> > addition, to LINK_PIE_SPEC where it belongs.  Doing that showed
> > another problem in gnu-user.h, with PIE_SPEC and NO_PIE_SPEC selection
> > of crtbegin*.o not properly hooked into a chain of if .. elseif ..
> > conditions, which required both PIE_SPEC and NO_PIE_SPEC to exclude
> > -static and -shared.  Fixing that particular problem finally allows
> > PIE_SPEC to serve just one purpose, and NO_PIE_SPEC to disappear.
> >
> > Bootstrapped and regression tested powerpc64le-linux c,c++.  No
> > regressions and a bunch of --enable-default-pie failures squashed.
> > OK mainline and active branches?
> >
> > Incidentally, there is a fairly strong case to be made for adding
> > -static to the -shared, -pie, -no-pie chain of RejectNegative's in
> > common.opt.  Since git 0d6378a9e (svn r48039) 2001-11-15, -static has
> > done more than just the traditional "prevent linking with dynamic
> > libraries", as -static selects crtbeginT.o rather than crtbegin.o
> > on GNU systems.  Realizing this is what led me to close pr80044, which
> > I'd opened with the aim of making -pie -static work together (with the
> > traditional meaning of -static).  I don't that is worth doing, but
> > mention pr80044 in the changelog due to fixing the insane output
> > produced by -pie -static with --disable-default-pie.
> >
> 
> On x86-64, without --enable-default-pie, "-static -pie" and "-pie -static"
> never worked since both -static and -pie are passed to linker, which
> uses libc.a to build PIE.

Yes, it's broken.

>  With --enable-default-pie, -static and -pie
> override each other.

No they don't.  -static overrides -pie.

>  What does your patch do on x86-64?  Make
> with and without --enable-default-pie behave the same?

Yes, as I said in my original post first paragraph.

>  Does it
> mean that both fail to create executable?

I try to leave that sort of patch to those better qualified.
Bootstrap and regression testing on x86_64-linux both
--enable-default-pie and --disable-default-pie was complete June 23.

-- 
Alan Modra
Australia Development Lab, IBM



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