Any updates? All gcc builders, including nightly performance tests, are failing.

No real progress. :-(

The following revision refers to this bug:
  https://chromium.googlesource.com/chromiumos/overlays/chromiumos-overlay/+/fe506eceab9eb805ca87d8ae73215476c53fe9a5

commit fe506eceab9eb805ca87d8ae73215476c53fe9a5
Author: Caroline Tice <cmtice@google.com>
Date: Thu Jan 05 00:24:47 2017

[GCC] Fix building gcc with USE='next_gcc'.

A change committed upstream in Feb. 2016 is causing the next_gcc
emerges to fail.  This CL applies a patch to GCC, when building
with USE='next_gcc', that undoes the upstream fix.  This is
intended to be a temporary workaround while we investigate and fix
the actual problem with the upstream change.

BUG= chromium:673427 
TEST=Emerged gcc, using USE='next_gcc' with this CL.

Change-Id: I284ab9cfcebc3afb03dcee1b7d2790da41debb36
Reviewed-on: https://chromium-review.googlesource.com/424958
Commit-Ready: Caroline Tice <cmtice@chromium.org>
Tested-by: Caroline Tice <cmtice@chromium.org>
Reviewed-by: Yunlian Jiang <yunlian@chromium.org>

[modify] https://crrev.com/fe506eceab9eb805ca87d8ae73215476c53fe9a5/sys-devel/gcc/gcc-9999.ebuild
[add] https://crrev.com/fe506eceab9eb805ca87d8ae73215476c53fe9a5/sys-devel/gcc/files/gcc-4.9-gcc_next-fixincludes.patch

The following revision refers to this bug:
  https://chromium.googlesource.com/chromiumos/overlays/chromiumos-overlay/+/74f0864e63620c2312dd0f858c0354a5114909f6

commit 74f0864e63620c2312dd0f858c0354a5114909f6
Author: Caroline Tice <cmtice@google.com>
Date: Fri Jan 06 17:43:57 2017

[GCC] Undo temporary patch from CL 424958

CL 424958 added a temporary patch to fix building with next_gcc,
while we found and fixed the real issue.  The real issue has been
found and fixed in the GCC repository, so the temporary patch
is no longer needed; this CL removes it.

BUG= chromium:673427 
TEST=Emerged gcc_next with this CL.

Change-Id: I39fb43214290872637844acc579a7e44368316ee
Reviewed-on: https://chromium-review.googlesource.com/425821
Commit-Ready: Caroline Tice <cmtice@chromium.org>
Tested-by: Caroline Tice <cmtice@chromium.org>
Reviewed-by: Mike Frysinger <vapier@chromium.org>
Reviewed-by: Yunlian Jiang <yunlian@chromium.org>

[modify] https://crrev.com/74f0864e63620c2312dd0f858c0354a5114909f6/sys-devel/gcc/gcc-9999.ebuild
[delete] https://crrev.com/f8dea149c230bd061d3664c78c1924a94cfa914e/sys-devel/gcc/files/gcc-4.9-gcc_next-fixincludes.patch

We finally got the issues fixed with downloading and building the GCC "next" compiler in ChromeOS. However, now that we've got the compiler it's consistently failing to build 3-4 packages (depending on which architecture you're using):  

sys-devel/binutils  (all archs)
net-misc/iperf (all archs)
chromeos-base/verify (all archs)
dev-libs/boost (arm, arm64, x86_64)

I'm in the process of investigating and trying to fix this now.

 Issue 682426  has been merged into this issue.

The following change has been committed to the svn branch for this GCC compiler. It should fix the problem...give the svn mirrors about 24 hours to pick up the change.

Index: libstdc++-v3/configure.host
===================================================================
--- libstdc++-v3/configure.host	(revision 244382)
+++ libstdc++-v3/configure.host	(working copy)
@@ -81,7 +81,7 @@
 # Try to guess a default cpu_include_dir based on the name of the CPU.  We
 # cannot do this for os_include_dir; there are too many portable operating
 # systems out there.  :-)
-c_model=c_google
+c_model=c_global
 c_compatibility=no
 atomic_word_dir=cpu/generic
 atomic_flags=""
Index: libstdc++-v3/include/tr1/complex
===================================================================
--- libstdc++-v3/include/tr1/complex	(revision 244382)
+++ libstdc++-v3/include/tr1/complex	(working copy)
@@ -316,8 +316,8 @@
     {
       typedef typename __gnu_cxx::__promote<_Tp>::__type __type;
 #if (_GLIBCXX_USE_C99_MATH && !_GLIBCXX_USE_C99_FP_MACROS_DYNAMIC)
-      return ::signbit(__x) ? __type(3.1415926535897932384626433832795029L)
-	                    : __type();
+      return std::signbit(__x) ? __type(3.1415926535897932384626433832795029L)
+	                       : __type();
 #else
       return std::arg(std::complex<__type>(__x));
 #endif