[Bug boehm-gc/66848] New: boehm-gc fails test suite on x86_64-apple-darwin15

[howarth.at.gcc at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66848

            Bug ID: 66848
           Summary: boehm-gc fails test suite on x86_64-apple-darwin15
           Product: gcc
           Version: 5.2.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: boehm-gc
          Assignee: unassigned at gcc dot gnu.org
          Reporter: howarth.at.gcc at gmail dot com
  Target Milestone: ---

The boehm-gc test suite in FSF gcc shows regressions at -m32/-m64 when run on
x86_64-apple-darwin15...

WARNING: program timed out.
FAIL: boehm-gc.c/gctest.c -O2 execution test
FAIL: boehm-gc.c/thread_leak_test.c -O2 execution test

FAIL: boehm-gc.lib/staticrootstest.c -O2 execution test

The same regressions are seen when running the boehm-gc test suite binaries and
libraries, built entirely on x86_64-apple-darwin14, on x86_64-apple-darwin15.
Replacing the libunwind.dylib on x86_64-apple-darwin15 with one from
x86_64-apple-darwin14 eliminates the boehm-gc test suite regressions.

This issue has been opened as radr://21372179, "the FSF boehm-gc library built
on
10.10 fails to pass its tests on 10.11". The Apple programmers claim the
sources for libunwind.dylib are unchanged between darwin14 and darwin15. The
only difference is the use of the darwin15 SDK and the Xcode 7 clang compilers.
They believe the optimizations applied by the newer clang compiler are safe
(which seems to be supported by the fact that upstream boehm-gc from
http://www.hboehm.info/gc/ shows no test suite failures when built and run
under x86_64-apple-darwin15 with Xcode 7). Rather, they suspect we are tripping
over a latent bug in the FSF gcc boehm-gc sources.