re PR c++/64527 (Constructor for empty struct not called in some situations)

Fix PR c++/64527

gcc/
	PR c++/64527
	* gimplify.c (gimplify_init_constructor): Always emit a
	side-effecting constructor.

gcc/testsuite/
	PR c++/64527
	* g++.dg/init/pr64527.C: New test.

From-SVN: r222176

gcc/ChangeLog

+2015-04-17  Patrick Palka  <ppalka@gcc.gnu.org>
+
+	PR c++/64527
+	* gimplify.c (gimplify_init_constructor): Always emit a
+	side-effecting constructor.
+
 2015-04-17  Tom de Vries  <tom@codesourcery.com>
 
 	PR tree-optimization/64950

gcc/gimplify.c

@@ -3994,6 +3994,9 @@ gimplify_init_constructor (tree *expr_p, gimple_seq *pre_p, gimple_seq *post_p,
 					pre_p, post_p, &preeval_data);
 	  }
 
+	bool ctor_has_side_effects_p
+	  = TREE_SIDE_EFFECTS (TREE_OPERAND (*expr_p, 1));
+
 	if (cleared)
 	  {
 	    /* Zap the CONSTRUCTOR element list, which simplifies this case.
@@ -4006,9 +4009,11 @@ gimplify_init_constructor (tree *expr_p, gimple_seq *pre_p, gimple_seq *post_p,
 	  }
 
 	/* If we have not block cleared the object, or if there are nonzero
-	   elements in the constructor, add assignments to the individual
-	   scalar fields of the object.  */
-	if (!cleared || num_nonzero_elements > 0)
+	   elements in the constructor, or if the constructor has side effects,
+	   add assignments to the individual scalar fields of the object.  */
+	if (!cleared
+	    || num_nonzero_elements > 0
+	    || ctor_has_side_effects_p)
 	  gimplify_init_ctor_eval (object, elts, pre_p, cleared);
 
 	*expr_p = NULL_TREE;

gcc/testsuite/ChangeLog

+2015-04-17  Patrick Palka  <ppalka@gcc.gnu.org>
+
+	PR c++/64527
+	* g++.dg/init/pr64527.C: New test.
+
 2015-04-17  Tom de Vries  <tom@codesourcery.com>
 	    Michael Matz  <matz@suse.de>
 

gcc/testsuite/g++.dg/init/pr64527.C

+// { dg-do run { target c++11 } }
+
+static int g;
+
+struct A {
+  A() { g = 1; }
+};
+
+struct accessor {
+  A a;
+  int x;
+};
+
+int
+main (void)
+{
+  (void) accessor{};
+
+  if (g != 1)
+    __builtin_abort ();
+}