--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/gcc/testsuite/gcc.dg/Wreturn-local-addr-10.c	Thu Feb 13 11:34:05 2020 +0900
@@ -0,0 +1,56 @@
+/* PR c/71924 - missing -Wreturn-local-addr returning alloca result
+   Test reduced from libstdc++-v3/testsuite/ext/ext_pointer/1.cc.
+   It verifies that iteration in find_implicit_erroneous_behavior
+   in gimple-ssa-isolate-path.c terminates under specific conditions.
+   { dg-do compile }
+   { dg-options "-O2 -Wall" } */
+
+typedef __UINTPTR_TYPE__ uintptr_t;
+
+struct A { int i; };
+struct P { uintptr_t d; };
+
+static inline struct A* get (const struct P *p)
+{
+  if (p->d == 1)
+    return 0;
+
+  return (struct A*)((uintptr_t)p + p->d);
+}
+
+static inline void set (struct P *p, struct A* q)
+{
+  /* The basic block below would cause an infinite loop in
+     find_implicit_erroneous_behavior due to assuming the DUPLICATE
+     pointer returned from isolate_path would distinct from the one
+     passed to it.  (Replacing the if statement with the ternary ?:
+     expression did not have this effect (it gets optimized early
+     on).
+    <bb 4> [local count: 1073741823]:
+    # _14 = PHI <0B(2), &MEM <struct A[2]> [(void *)&a + 4B](3)>
+    _2 = _14->i;
+    if (_2 != 2)
+      goto <bb 5>; [0.00%]
+    else
+      goto <bb 6>; [100.00%]
+  */
+  if (!q)
+    p->d = 1;
+  else
+    p->d = (uintptr_t)(q) - (uintptr_t)(p);
+}
+
+void f (void)
+{
+  struct A a[2] = { { 1 }, { 2 } };
+
+  struct P p, q;
+  set (&p, a);
+  set (&q, get (&p));
+
+  set (&q, get (&q) + 0);
+  set (&q, get (&q) + 1);
+
+  if (get (&q)[0].i != get (&p)[1].i)
+    __builtin_abort ();
+}