[Bug c++/68642] New: GCC crashes on deep std::make_index_sequence

[wmhkebe at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=68642

            Bug ID: 68642
           Summary: GCC crashes on deep std::make_index_sequence
           Product: gcc
           Version: 5.2.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: wmhkebe at gmail dot com
  Target Milestone: ---

Created attachment 36884
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=36884&action=edit
Preprocessed file that will crash the compiler.

Compiling code containing std::make_index_sequence with moderately large N
(~100k) will crash g++. This is illustrated by the following code snippet,
which should be compiled with g++ -std=c++14 -ftemplate-depth=200000 (a
preprocessed file is also attached):

#include <utility>

int main() {
  std::make_index_sequence<100000> a;
  return 0;
}

Compiler output:
g++-5: internal compiler error: Segmentation fault: 11 (program cc1plus)
Please submit a full bug report,
with preprocessed source if appropriate.
See <https://github.com/Homebrew/homebrew-versions/issues> for instructions.

Output from g++ -v:
Using built-in specs.
COLLECT_GCC=gcc-5
COLLECT_LTO_WRAPPER=/Users/menghui/homebrew/Cellar/gcc5/5.2.0/libexec/gcc/x86_64-apple-darwin14.5.0/5.2.0/lto-wrapper
Target: x86_64-apple-darwin14.5.0
Configured with: ../configure --build=x86_64-apple-darwin14.5.0
--prefix=/Users/menghui/homebrew/Cellar/gcc5/5.2.0
--libdir=/Users/menghui/homebrew/Cellar/gcc5/5.2.0/lib/gcc/5
--enable-languages=c,c++,objc,obj-c++ --program-suffix=-5
--with-gmp=/Users/menghui/homebrew/opt/gmp
--with-mpfr=/Users/menghui/homebrew/opt/mpfr
--with-mpc=/Users/menghui/homebrew/opt/libmpc
--with-isl=/Users/menghui/homebrew/opt/isl014 --with-system-zlib
--enable-libstdcxx-time=yes --enable-stage1-checking --enable-checking=release
--enable-lto --disable-werror --with-pkgversion='Homebrew gcc5 5.2.0'
--with-bugurl=https://github.com/Homebrew/homebrew-versions/issues
--enable-plugin --disable-nls --enable-multilib
Thread model: posix
gcc version 5.2.0 (Homebrew gcc5 5.2.0)