--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/gcc/testsuite/c-c++-common/pr51628-26.c	Thu Feb 13 11:34:05 2020 +0900
@@ -0,0 +1,33 @@
+/* PR c/51628.  */
+/* { dg-do compile } */
+/* { dg-options "-O" } */
+
+struct A {
+  int i;
+} __attribute__ ((packed));
+
+struct A p = {1};
+int *addr;
+
+int i, j;
+
+void
+foo1 (void)
+{
+  addr = (i = -1, &p.i);
+/* { dg-warning "may result in an unaligned pointer value" "" { target *-*-* } .-1 } */
+}
+
+void
+foo2 (void)
+{
+  addr = (i = -1, j = -2, &p.i);
+/* { dg-warning "may result in an unaligned pointer value" "" { target *-*-* } .-1 } */
+}
+
+void
+foo3 (void)
+{
+  addr = (i = -1, (j = -2, &p.i));
+/* { dg-warning "may result in an unaligned pointer value" "" { target *-*-* } .-1 } */
+}