--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/gcc/testsuite/gcc.dg/pr56078.c	Fri Oct 27 22:46:09 2017 +0900
@@ -0,0 +1,25 @@
+/* PR c/56078 */
+/* { dg-do run } */
+/* { dg-options "-std=gnu99" } */
+
+typedef __SIZE_TYPE__ size_t;
+extern int memcmp (const void *, const void *, size_t);
+extern void abort (void);
+
+struct T { int a; char b[]; };
+struct T t1 = { .a = 1, .b = "abcd", .b[0] = '2' };
+struct T t2 = { .a = 1, .b = "2bcd" };
+struct T t3 = { .a = 1, .b[2] = 'a' };
+struct T t4 = { .a = 1, .b = { '\0', '\0', 'a' } };
+struct T t5 = { .a = 1, .b = { [0] = 'a', [1] = 'b', [2] = 'c' } };
+struct T t6 = { .a = 1, .b[2] = 'c', .b[1] = 'x', .b[0] = 'a', .b[1] = 'b' };
+
+int
+main ()
+{
+  if (memcmp (t1.b, t2.b, sizeof ("abcd")) != 0
+      || memcmp (t3.b, t4.b, 3) != 0
+      || memcmp (t5.b, t6.b, 3) != 0)
+    abort ();
+  return 0;
+}