re PR c++/36408 (ICE with statement expression in template)

Fix PR c++/36408

gcc/cp/ChangeLog:

	PR c++/36408
	* cp-tree.h (empty_expr_stmt_p): Declare ...
	* semantics.c (empty_expr_stmt_p): ... this.
	* pt.c (tsubst_copy_and_build) <STMT_EXPR>: Use it.

gcc/testsuite/ChangeLog:
	PR c++/36408
	* g++.dg/template/stmtexpr2.C: New test.

From-SVN: r154731

gcc/cp/ChangeLog

+2009-11-28  Dodji Seketeli  <dodji@redhat.com>
+
+	PR c++/36408
+	* cp-tree.h (empty_expr_stmt_p): Declare ...
+	* semantics.c (empty_expr_stmt_p): ... this.
+	* pt.c (tsubst_copy_and_build) <STMT_EXPR>: Use it.
+
 2009-11-27  Paolo Carlini  <paolo.carlini@oracle.com>
 
 	PR c++/38656

gcc/cp/cp-tree.h

@@ -5074,6 +5074,7 @@ extern tree begin_stmt_expr			(void);
 extern tree finish_stmt_expr_expr		(tree, tree);
 extern tree finish_stmt_expr			(tree, bool);
 extern tree stmt_expr_value_expr		(tree);
+bool empty_expr_stmt_p				(tree);
 extern tree perform_koenig_lookup		(tree, VEC(tree,gc) *);
 extern tree finish_call_expr			(tree, VEC(tree,gc) **, bool,
 						 bool, tsubst_flags_t);

gcc/cp/pt.c

@@ -12544,6 +12544,11 @@ tsubst_copy_and_build (tree t,
 	stmt_expr = finish_stmt_expr (stmt_expr, false);
 	cur_stmt_expr = old_stmt_expr;
 
+	/* If the resulting list of expression statement is empty,
+	   fold it further into void_zero_node.  */
+	if (empty_expr_stmt_p (cur_stmt_expr))
+	  cur_stmt_expr = void_zero_node;
+
 	return stmt_expr;
       }
 

gcc/cp/semantics.c

@@ -1847,6 +1847,32 @@ stmt_expr_value_expr (tree stmt_expr)
   return t;
 }
 
+/* Return TRUE iff EXPR_STMT is an empty list of
+   expression statements.  */
+
+bool
+empty_expr_stmt_p (tree expr_stmt)
+{
+  tree body = NULL_TREE;
+
+  if (expr_stmt)
+    {
+      if (TREE_CODE (expr_stmt) == EXPR_STMT)
+	body = EXPR_STMT_EXPR (expr_stmt);
+      else if (TREE_CODE (expr_stmt) == STATEMENT_LIST)
+	body = expr_stmt;
+    }
+
+    if (body)
+      {
+	if (TREE_CODE (body) == STATEMENT_LIST)
+	  return tsi_end_p (tsi_start (body));
+	else
+	  return empty_expr_stmt_p (body);
+      }
+  return false;
+}
+
 /* Perform Koenig lookup.  FN is the postfix-expression representing
    the function (or functions) to call; ARGS are the arguments to the
    call.  Returns the functions to be considered by overload

gcc/testsuite/ChangeLog

+2009-11-28  Dodji Seketeli  <dodji@redhat.com>
+
+	PR c++/36408
+	* g++.dg/template/stmtexpr2.C: New test.
+
 2009-11-28  Richard Guenther  <rguenther@suse.de>
 
 	PR tree-optimization/42183

gcc/testsuite/g++.dg/template/stmtexpr2.C

+// Contributed by Dodji Seketeli <dodji@redhat.com>
+// Origin: PR c++/36408
+// { dg-options "" }
+// { dg-do compile }
+
+template<int>
+void
+foo()
+{
+  int i = ({ }); // { dg-error "void value not ignored" }
+}
+
+template<int>
+void
+bar()
+{
+  int i = ({ ({}); }); // { dg-error "void value not ignored" }
+}
+
+int
+main ()
+{
+  foo<0> ();
+  bar<0> ();
+}
+