re PR c/17855 (modification of function struct return not diagnosed)

	PR c/17855
	* gimplify.c (gimplify_expr): Create a temporary for lvalue
	COND_EXPR and CALL_EXPR.

testsuite:
	* gcc.c-torture/compile/struct-non-lval-1.c,
	gcc.c-torture/compile/struct-non-lval-2.c,
	gcc.c-torture/compile/struct-non-lval-3.c: New tests.

From-SVN: r97352

gcc/ChangeLog

+2005-04-01  Joseph S. Myers  <joseph@codesourcery.com>
+
+	PR c/17855
+	* gimplify.c (gimplify_expr): Create a temporary for lvalue
+	COND_EXPR and CALL_EXPR.
+
 2005-03-31  Vladimir Makarov  <vmakarov@redhat.com>
 
 	PR target/20632

gcc/gimplify.c

@@ -3810,10 +3810,28 @@ gimplify_expr (tree *expr_p, tree *pre_p, tree *post_p,
 	case COND_EXPR:
 	  ret = gimplify_cond_expr (expr_p, pre_p, post_p, NULL_TREE,
 				    fallback);
+	  /* C99 code may assign to an array in a structure value of a
+	     conditional expression, and this has undefined behavior
+	     only on execution, so create a temporary if an lvalue is
+	     required.  */
+	  if (fallback == fb_lvalue)
+	    {
+	      *expr_p = get_initialized_tmp_var (*expr_p, pre_p, post_p);
+	      lang_hooks.mark_addressable (*expr_p);
+	    }
 	  break;
 
 	case CALL_EXPR:
 	  ret = gimplify_call_expr (expr_p, pre_p, fallback != fb_none);
+	  /* C99 code may assign to an array in a structure returned
+	     from a function, and this has undefined behavior only on
+	     execution, so create a temporary if an lvalue is
+	     required.  */
+	  if (fallback == fb_lvalue)
+	    {
+	      *expr_p = get_initialized_tmp_var (*expr_p, pre_p, post_p);
+	      lang_hooks.mark_addressable (*expr_p);
+	    }
 	  break;
 
 	case TREE_LIST:

gcc/testsuite/ChangeLog

+2005-04-01  Joseph S. Myers  <joseph@codesourcery.com>
+
+	PR c/17855
+	* gcc.c-torture/compile/struct-non-lval-1.c,
+	gcc.c-torture/compile/struct-non-lval-2.c,
+	gcc.c-torture/compile/struct-non-lval-3.c: New tests.
+
 2005-03-31  Janis Johnson  <janis187@us.ibm.com>
 
 	* gcc.dg/tls/tls.exp: Remove temporary file.

gcc/testsuite/gcc.c-torture/compile/struct-non-lval-1.c

+/* Bug c/17855.  */
+struct foo {char x, y, z[2];};
+struct foo f();
+void bar(int baz)
+{
+  f().z[baz] = 1;
+}

gcc/testsuite/gcc.c-torture/compile/struct-non-lval-2.c

+/* Bug c/17855, using conditional expression for non-lvalue.  */
+struct foo {char x, y, z[2];};
+struct foo p, q; int r;
+void bar(int baz)
+{
+  (r ? p : q).z[baz] = 1;
+}

gcc/testsuite/gcc.c-torture/compile/struct-non-lval-3.c

+/* Bug c/17855, using assignment for non-lvalue.  */
+struct foo {char x, y, z[2];};
+struct foo p, q;
+void bar(int baz)
+{
+  (p = q).z[baz] = 1;
+}