re PR c++/79822 (ICE with void statement expression)

	PR c++/79822
	* constexpr.c (cxx_eval_statement_list): Treat empty ({ }) like
	({ (void) 0; }).

	* g++.dg/cpp0x/constexpr-79822.C: New test.

From-SVN: r245925

gcc/cp/ChangeLog

+2017-03-06  Jakub Jelinek  <jakub@redhat.com>
+
+	PR c++/79822
+	* constexpr.c (cxx_eval_statement_list): Treat empty ({ }) like
+	({ (void) 0; }).
+
 2017-03-06  Jason Merrill  <jason@redhat.com>
 
 	Revert "Allow deduction guides to look into primary template."

gcc/cp/constexpr.c

@@ -3725,8 +3725,9 @@ cxx_eval_statement_list (const constexpr_ctx *ctx, tree t,
 {
   tree_stmt_iterator i;
   tree local_target;
-  /* In a statement-expression we want to return the last value.  */
-  tree r = NULL_TREE;
+  /* In a statement-expression we want to return the last value.
+     For empty statement expression return void_node.  */
+  tree r = void_node;
   if (!jump_target)
     {
       local_target = NULL_TREE;

gcc/testsuite/ChangeLog

+2017-03-06  Jakub Jelinek  <jakub@redhat.com>
+
+	PR c++/79822
+	* g++.dg/cpp0x/constexpr-79822.C: New test.
+
 2017-03-06  Richard Biener  <rguenther@suse.de>
 
 	PR tree-optimization/79894

gcc/testsuite/g++.dg/cpp0x/constexpr-79822.C

+// PR c++/79822
+// { dg-do compile }
+// { dg-options "" }
+
+bool
+foo ()
+{
+  bool a = ({ }) && false;		// { dg-error "could not convert" }
+  bool b = ({ ; }) && false;		// { dg-error "could not convert" }
+  bool c = ({ (void) 1; }) && false;	// { dg-error "could not convert" }
+  return a && b && c;
+}