[Bug c++/68470] New: Internal Compiler Error observed by g++-4.9.2 and a few other versions (reported to Debian)

["zephyrus8080 at gmail dot com" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=68470

            Bug ID: 68470
           Summary: Internal Compiler Error observed by g++-4.9.2 and a
                    few other versions (reported to Debian)
           Product: gcc
           Version: 4.9.2
               URL: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=8056
                    16
            Status: UNCONFIRMED
          Severity: major
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: zephyrus8080 at gmail dot com
  Target Milestone: ---
              Host: amd86
            Target: amd86

Can someone kindly take a look at GCC internal compiler error reported to
Debian bug tracker?

https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=805616

The first report was only for g++-4.9.2 and the
preprocessed input file (compressed)is at the same URL and
is retrieved as
https://bugs.debian.org/cgi-bin/bugreport.cgi?att=1;msg=5;filename=ccdWdyDf.out.gz;bug=805616

The command line that triggere/usr/bin/g++-4.9 -fno-builtin-strlen
-Wl,--gdb-index
-B/home/ishikawa/bin -Wl,--gdb-index -o Unified_cpp_gfx_2d0.o -c
-I../../dist/stl_wrappers -I../../dist/system_wrappers -include
/new-hd1/extra/ishikawa/TB-3HG/NEW-COMMSRC/mozilla/config/gcc_hidden.h
-DUSE_SSE2 -DOS_POSIX=1 -DOS_LINUX=1 -DUSE_CAIRO -DMOZ2D_HAS_MOZ_CAIRO
-DMOZ_ENABLE_FREETYPE -DSTATIC_EXPORTABLE_JS_API -DMOZILLA_INTERNAL_API
-DIMPL_LIBXUL -I/new-hd1/extra/ishikawa/TB-3HG/NEW-COMMSRC/mozilla/gfx/2d
-I. -I../../ipc/ipdl/_ipdlheaders
-I/new-hd1/extra/ishikawa/TB-3HG/NEW-COMMSRC/mozilla/ipc/chromium/src
-I/new-hd1/extra/ishikawa/TB-3HG/NEW-COMMSRC/mozilla/ipc/glue
-I/new-hd1/extra/ishikawa/TB-3HG/NEW-COMMSRC/mozilla/gfx/skia
-I/new-hd1/extra/ishikawa/TB-3HG/NEW-COMMSRC/mozilla/gfx/skia/skia/include/config
-I/new-hd1/extra/ishikawa/TB-3HG/NEW-COMMSRC/mozilla/gfx/skia/skia/include/core
-I/new-hd1/extra/ishikawa/TB-3HG/NEW-COMMSRC/mozilla/gfx/skia/skia/include/gpu
-I/new-hd1/extra/ishikawa/TB-3HG/NEW-COMMSRC/mozilla/gfx/skia/skia/include/utils
-I../../dist/include -I/home/ishikawa/objdir-tb3/dist/include/nspr
-I/home/ishikawa/objdir-tb3/dist/include/nss -fPIC -DMOZILLA_CLIENT -include
../../mozilla-config.h -MD -MP -MF .deps/Unified_cpp_gfx_2d0.o.pp -Wall
-Wempty-body -Woverloaded-virtual -Wsign-compare -Wwrite-strings
-Wno-invalid-offsetof -Wcast-align -fno-exceptions -fno-strict-aliasing
-fno-rtti -fno-exceptions -fno-math-errno -std=gnu++0x -pthread -pipe
-DDEBUG -DTRACING -gsplit-dwarf -g -O2 -freorder-blocks
-fno-omit-frame-pointer -I/home/ishikawa/objdir-tb3/dist/include/cairo
-I/usr/include/freetype2 -I/usr/include/freetype2
/home/ishikawa/objdir-tb3/gfx/2d/Unified_cpp_gfx_2d0.cppd the error was:


In the followup to the original Debian bug report, someone else followed up
and simplified the test case and according to the post:
https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=805616#10

--- begin quote

Minimizing the example to something managable ... and understood by different
compiler versions as well

4.9.4 (SVN): segfault
4.9.3-5 (Debian): segfault
4.8.5-1 (Debian): pass
4.7.4-3 (Debian): compile error
5.2.1-23 (Debian): segfault, different backtrace

--- end quote.

The simplified preprocessed input is
in the web URL and retrieved as
https://bugs.debian.org/cgi-bin/bugreport.cgi?filename=805616_min.hM.min.ii;msg=10;att=1;bug=805616

and the command line to trigger the bug is in the web, too: I am quoting it
here.

g++-4.9.x -v -std=gnu++11 -O2 -c 805616_min.hM.min.ii
Using built-in specs.
COLLECT_GCC=/opt/software/x86_64/gcc-4.9.x/bin/g++-4.9.x
Target: x86_64-unknown-linux-gnu
Configured with: ../gcc-4_9-branch/configure
--prefix=/opt/software/x86_64/gcc-4.9.x --program-suffix=-4.9.x
--enable-languages=c,c++,fortran --enable-checking
Thread model: posix
gcc version 4.9.4 20151121 (prerelease) (GCC) 
COLLECT_GCC_OPTIONS='-v' '-std=gnu++11' '-O2' '-c' '-shared-libgcc'
'-mtune=generic' '-march=x86-64'

/opt/software/x86_64/gcc-4.9.x/libexec/gcc/x86_64-unknown-linux-gnu/4.9.4/cc1plus
-fpreprocessed 805616_min.hM.min.ii -quiet -dumpbase 805616_min.hM.min.ii
-mtune=generic -march=x86-64 -auxbase 805616_min.hM.min -O2 -std=gnu++11
-version -o /tmp/ccdwpTpg.s

Please see the gory detail in the original web and I believe the original
posters are happy to answer the questions.

TIA