[Bug c++/67650] New: undef reference with -fdevirtualize

[vincent.lextrait at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67650

            Bug ID: 67650
           Summary: undef reference with -fdevirtualize
           Product: gcc
           Version: 5.2.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: vincent.lextrait at gmail dot com
  Target Milestone: ---

I get an undefined symbol when using -O2, more specifically, after trying all
additional options on top of -O1, this is due to -fdevirtualize. With -O1
-devirtualize, the symbol is missing. It's not missing with just -O1.
The symbol is a virtual member function of a class template.
I checked that the issue does not occur with gcc-4.9.2, it is new in gcc-5.

Is it worth it to try reducing my code and produce a code snippet exhibiting
the issue? Or is the issue known already? I didn't find any track of it.

gcc version:
/usr/local/bin/g++-5 -v
Using built-in specs.
COLLECT_GCC=/usr/local/bin/g++-5
COLLECT_LTO_WRAPPER=/usr/local/Cellar/gcc/5.2.0/libexec/gcc/x86_64-apple-darwin14.4.0/5.2.0/lto-wrapper
Target: x86_64-apple-darwin14.4.0
Configured with: ../configure --build=x86_64-apple-darwin14.4.0
--prefix=/usr/local/Cellar/gcc/5.2.0
--libdir=/usr/local/Cellar/gcc/5.2.0/lib/gcc/5
--enable-languages=c,c++,objc,obj-c++,fortran --program-suffix=-5
--with-gmp=/usr/local/opt/gmp --with-mpfr=/usr/local/opt/mpfr
--with-mpc=/usr/local/opt/libmpc --with-isl=/usr/local/opt/isl
--with-system-zlib --enable-libstdcxx-time=yes --enable-stage1-checking
--enable-checking=release --enable-lto --with-build-config=bootstrap-debug
--disable-werror --with-pkgversion='Homebrew gcc 5.2.0'
--with-bugurl=https://github.com/Homebrew/homebrew/issues --enable-plugin
--disable-nls --enable-multilib
Thread model: posix
gcc version 5.2.0 (Homebrew gcc 5.2.0)