Comment 2 for bug 1432529

In the past, I had no problems building sbcl on the same 2 x86 boxes. I don't use hardened. Recent software upgrades were glibc 2.19 -> 2.20, gcc 4.8.3 -> 4.9.2. The failure is identical on 2 computers, so, hardware memory fauts are out of question.
Is there any way to investigate what's going on? From the buildlog I see that the (downloaded) binary sbcl-1.2.7 has done its work normally (or so it seems), and has produced an sbcl-1.2.9 executable. But warm init fails:

./src/runtime/sbcl --core output/cold-sbcl.core --lose-on-corruption --no-sysinit --no-userinit
<skipped>
COLD-INIT... (PACKAGE = "COMMON-LISP")
("Length(TLFs)= " 24692)
CORRUPTION WARNING in SBCL pid 2441:
Memory fault at (nil) (pc=0x80625d0, sp=0xb39becb8)
The integrity of this image is possibly compromised.

What can I investigate further? I'm the maintainer of maxima and fricas, as well as common lisps which can compile them, in Gentoo. I *have* to find out what's going wrong on x86.