[C++ PATCH] Add test for c++/77771

[Marek Polacek]

This was fixed by r250659.

Tested on x86_64-linux, applying to trunk.

2019-06-07  Marek Polacek  <pola...@redhat.com>

        PR c++/77771
        * g++.dg/cpp0x/constexpr-77771.C: New test.

diff --git gcc/testsuite/g++.dg/cpp0x/constexpr-77771.C 
gcc/testsuite/g++.dg/cpp0x/constexpr-77771.C
new file mode 100644
index 00000000000..fca83d92f6a
--- /dev/null
+++ gcc/testsuite/g++.dg/cpp0x/constexpr-77771.C
@@ -0,0 +1,16 @@
+// PR c++/77771
+// { dg-do compile { target c++11 } }
+// { dg-options "-O" }
+
+struct S
+{
+  char x[2];
+  unsigned y;
+};
+
+constexpr bool func(const S s)
+{
+    return s.x[0] != 42 || s.x[1] != 0;
+}
+
+static_assert(func({{42, 7}, 0}), "");