--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/gcc/testsuite/gcc.dg/pr46921.c	Thu Oct 25 07:37:49 2018 +0900
@@ -0,0 +1,40 @@
+/* PR c/46921  lost side effect when struct initializer expr uses comma
+      operator  */
+
+/* { dg-do run } */
+/* { dg-options "" } */
+
+extern int printf(const char *, ...);
+extern void abort (void);
+
+typedef struct __uws_0 { } uw_unit;
+uw_unit uw_unit_v = {};
+
+struct __uws_1 
+{
+  struct __uws_0 __uwf_1;
+  struct __uws_1* __uwf_2;
+};
+
+static int left_hand_eval = 0;
+
+static void
+foo (const char *s)
+{
+  ++left_hand_eval;
+  printf("%s", s);
+}
+
+int
+main ()
+{
+  struct __uws_1 tmp = {(foo("Inner\n"), uw_unit_v)};
+  
+  printf("Outer\n");
+  /* left hand expression in comma operator initializer must always be
+     evaluated if there are side effects.  */
+  if (!left_hand_eval)
+    abort ();
+  
+  return 0;
+}