PR libstdc++/89446 fix null pointer dereference in char_traits

	PR libstdc++/89446
	* include/bits/char_traits.h (__constant_char_array): Check index is
	in range before dereferencing.
	* testsuite/21_strings/basic_string_view/operators/char/89446.cc:
	New test.

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/branches/gcc-8-branch@269144 138bc75d-0d04-0410-961f-82ee72b054a4
3 files changed