semantics.c (begin_stmt_expr): Avoid duplicating the effect of the expression in templates.

	* semantics.c (begin_stmt_expr): Avoid duplicating the effect of
	the expression in templates.
	(finish_stmt_expr): Likewise.

From-SVN: r19469

gcc/cp/ChangeLog

+Tue Apr 28 13:22:01 1998  Mark Mitchell  <mmitchell@usa.net>
+
+	* semantics.c (begin_stmt_expr): Avoid duplicating the effect of
+	the expression in templates.
+	(finish_stmt_expr): Likewise.
+
 1998-04-28  Brendan Kehoe  <brendan@cygnus.com>
 
 	* decl2.c (ambiguous_decl): Fix NAME parm to be a tree, not int.

gcc/cp/semantics.c

@@ -761,14 +761,18 @@ finish_parenthesized_expr (expr)
   return expr;
 }
 
-/* Begin a statement-expression.  Returns a new RTL_EXPR if
-   appropriate. */
+/* Begin a statement-expression.  The value returned must be passed to
+   finish_stmt_expr.  */
 
 tree 
 begin_stmt_expr ()
 {
   keep_next_level ();
-  return processing_template_decl ? NULL_TREE : expand_start_stmt_expr(); 
+  /* If we're processing_template_decl, then the upcoming compound
+     statement will be chained onto the tree structure, starting at
+     last_tree.  We return last_tree so that we can later unhook the
+     compound statement.  */
+  return processing_template_decl ? last_tree : expand_start_stmt_expr(); 
 }
 
 /* Finish a statement-expression.  RTL_EXPR should be the value
@@ -807,6 +811,14 @@ finish_stmt_expr (rtl_expr, expr)
     }
   else
     result = expr;
+
+  if (processing_template_decl)
+    {
+      /* Remove the compound statement from the tree structure; it is
+	 now saved in the BIND_EXPR.  */
+      last_tree = rtl_expr;
+      TREE_CHAIN (last_tree) = NULL_TREE;
+    }
   
   return result;
 }

gcc/testsuite/g++.old-deja/g++.pt/stmtexpr2.C

+extern "C" void abort();
+
+int i;
+
+void g()
+{
+  i++;
+}
+
+template <class T>
+void f(T)
+{
+  __extension__ ({g();});
+}
+
+int main()
+{
+  f(3.0);
+  if (i != 1)
+    abort();
+
+  return 0;
+}
+