https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80171
--- Comment #6 from Deniz Bahadir <D.Bahadir at GMX dot de> --- (In reply to Richard Biener from comment #3) > > Simple fix (further reduced testcase appreciated) CReduce originally created a radically reduced test-case which however was no valid C++ anymore. (My check script was not specific enough.) It always failed and should probably become another bug-report. Radically reduced invalid C++ test-case: ---------------------------------------- namespace mpl_ } namespace boost namespace mpl using namespace mpl_ } } namespace mpl_ template <T> struct integral_c; } namespace boost template <val> struct mpl::integral_c { However, I was able to adjust it slightly. (I am not sure if this is really valid C++14 code.) Radically reduced (valid?) C++ test-case: ----------------------------------------- namespace mpl_ {} namespace boost { namespace mpl { using namespace mpl_; } } namespace mpl_ { template <typename T> struct integral_c; } namespace boost { template <typename val> struct mpl::integral_c {}; } Both fail like this: The error: ---------- LANG=C /usr/bin/g++-6 -fpermissive -m64 -D_GLIBCXX_USE_CXX11_ABI=1 -std=c++14 -O0 -DNDEBUG -fPIC -c -w smalltestcase.i -o /dev/null g++-6: internal compiler error: Segmentation fault (program cc1plus) Please submit a full bug report, with preprocessed source if appropriate. See <file:///usr/share/doc/gcc-6/README.Bugs> for instructions.