[Committed] New testcase for C++/71792, bitfields and auto

This testcase used to fail before GCC 6.4.0 due to the wrong
type being used for auto when used with bitfields, the C++
front-end was using the "bitfield" type rather than the
underlaying type.

Committed the testcase after a quick check.

	PR c++/71792

gcc/testsuite/ChangeLog:

	* g++.dg/torture/pr71792.C: New test.

1 files changed, 42 insertions, 0 deletions

diff --git a/gcc/testsuite/g++.dg/torture/pr71792.C b/gcc/testsuite/g++.dg/torture/pr71792.C
new file mode 100644
index 0000000..607774d
--- /dev/null
+++ b/gcc/testsuite/g++.dg/torture/pr71792.C
@@ -0,0 +1,42 @@
+// { dg-do run { target c++11 } }
+// PR C++/71792
+
+class some_class
+{
+public:
+  unsigned int np              : 4;
+  unsigned int nc              : 8;
+  unsigned int nc0             : 1;
+};
+
+template<bool what>
+static void test_bug (const some_class &mp) {
+  if (what) {
+    int t = 0;
+    for (auto i = mp.nc0; i < mp.nc; i++) {
+      if (t != i) __builtin_abort ();
+      t++;
+    }
+  }
+}
+
+static void test_ok (const some_class &mp) {
+  int t = 0;
+  for (auto i = mp.nc0; i < mp.nc; i++) {
+    if (t != i) __builtin_abort ();
+    t++;
+  }
+}
+
+int main ()
+{
+  some_class mp;
+  mp.nc0 = 0;
+  mp.nc = 9;
+  mp.np = 3;
+
+  test_bug<true> (mp);
+  test_ok (mp);
+
+  return 0;
+}