diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 6d5ce8b27c2b..c6992fcb24fe 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,9 @@
+2001-01-04  Mark Mitchell  <mark@codesourcery.com>
+
+	* tree.c (copy_node): Remove documentation about obstacks.
+	(buidl1): Check that nobody tries to build 2-argument nodes this
+	way.
+
 2001-01-04  Kaveh R. Ghazi  <ghazi@caip.rutgers.edu>
 
 	* sparc.h (PREDICATE_CODES): Delete fp_sethi_p, fp_mov_p and
diff --git a/gcc/cp/ChangeLog b/gcc/cp/ChangeLog
index 7404a1a001ba..e86de6119cb8 100644
--- a/gcc/cp/ChangeLog
+++ b/gcc/cp/ChangeLog
@@ -1,3 +1,8 @@
+2001-01-04  Mark Mitchell  <mark@codesourcery.com>
+
+	* call.c (build_conv): Don't use build1 for USER_CONV.
+	* pt.c (tsubst_copy): Or for PREINCREMENT_EXPR and similar nodes.
+
 2001-01-03  Joseph S. Myers  <jsm28@cam.ac.uk>
 
 	* lex.c (lang_init): Call c_common_lang_init.
diff --git a/gcc/tree.c b/gcc/tree.c
index a836b99ea2aa..865aacd6e6a3 100644
--- a/gcc/tree.c
+++ b/gcc/tree.c
@@ -469,10 +469,7 @@ make_lang_type (code)
 }
 
 /* Return a new node with the same contents as NODE except that its
-   TREE_CHAIN is zero and it has a fresh uid.  Unlike make_node, this
-   function always performs the allocation on the CURRENT_OBSTACK;
-   it's up to the caller to pick the right obstack before calling this
-   function.  */
+   TREE_CHAIN is zero and it has a fresh uid.  */
 
 tree
 copy_node (node)
@@ -2424,6 +2421,13 @@ build1 (code, type, node)
     kind = e_kind;
 #endif
 
+#ifdef ENABLE_CHECKING
+  if (TREE_CODE_CLASS (code) == '2' 
+      || TREE_CODE_CLASS (code) == '<'
+      || TREE_CODE_LENGTH (code) != 1)
+    abort ();
+#endif /* ENABLE_CHECKING */
+
   length = sizeof (struct tree_exp);
 
   t = ggc_alloc_tree (length);