[Bug libstdc++/84865] New: Regular expression regex_search falls into infinite loop causing segfault on crayxc machines

["shaoqin2 at illinois dot edu" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=84865

            Bug ID: 84865
           Summary: Regular expression regex_search falls into infinite
                    loop causing segfault on crayxc machines
           Product: gcc
           Version: 5.3.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: libstdc++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: shaoqin2 at illinois dot edu
  Target Milestone: ---

Using regex_search in a multi threaded environment on crayxc super computer
will cause infinite loop and segfault. g++ information is here

Target: x86_64-suse-linux
Configured with: ../cray-gcc-5.3.0/configure 
--prefix=/opt/gcc/5.3.0/snos 
--disable-nls --libdir=/opt/gcc/5.3.0/snos/lib 
--enable-languages=c,c++,fortran 
--with-gxx-include-dir=/opt/gcc/5.3.0/snos/include/g++ 
--with-slibdir=/opt/gcc/5.3.0/snos/lib 
--with-system-zlib --enable-shared 
--enable-__cxa_atexit 
--build=x86_64-suse-linux 
--with-ppl --with-cloog
Thread model: posix
gcc version 5.3.0 20151204 (Cray Inc.) (GCC) 

uname -a
Linux edison11 4.4.103-92.56-default #1 SMP Wed Dec 27 16:24:31 UTC 2017
(2fd2155) x86_64 x86_64 x86_64 GNU/Linux


Command line to reproduce this segfault: 
(.cpp file is not attached per guideline. Feel free to ask me to post it, it's
super short and simple, I extracted minimum error reproducing code)

g++ -std=c++11 -save-temps regex.cpp -lpthread
./a.out
Segmentation fault (core dumped)