Merge branch 'bg/compiler-beam_validator' into ccase/r13b04_dev

* bg/compiler-beam_validator:
  beam_validator: fix incorrect assumptions about GC guard BIFs

OTP-8378  In rare circumstances when using garbaging collecting guard BIFs,
          the validation pass (beam_validator) would signal that the code
          was unsafe, when it in fact was correct. (Thanks to Kiran
          Khaladkar.)

1 files changed, 9 insertions, 5 deletions

diff --git a/erts/emulator/beam/erl_bif_guard.c b/erts/emulator/beam/erl_bif_guard.c
index 8b47db10dd..440b0b4f14 100644
--- a/erts/emulator/beam/erl_bif_guard.c
+++ b/erts/emulator/beam/erl_bif_guard.c
@@ -1,19 +1,19 @@
 /*
  * %CopyrightBegin%
- * 
- * Copyright Ericsson AB 2006-2009. All Rights Reserved.
- * 
+ *
+ * Copyright Ericsson AB 2006-2010. All Rights Reserved.
+ *
  * The contents of this file are subject to the Erlang Public License,
  * Version 1.1, (the "License"); you may not use this file except in
  * compliance with the License. You should have received a copy of the
  * Erlang Public License along with this software. If not, it can be
  * retrieved online at http://www.erlang.org/.
- * 
+ *
  * Software distributed under the License is distributed on an "AS IS"
  * basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See
  * the License for the specific language governing rights and limitations
  * under the License.
- * 
+ *
  * %CopyrightEnd%
  */
 
@@ -318,6 +318,10 @@ double_to_integer(Process* p, double x)
  * The following code is used when a guard that may build on the
  * heap is called directly. They must not use HAlloc(), but must
  * do a garbage collection if there is insufficient heap space.
+ *
+ * Important note: All error checking MUST be done before doing
+ * a garbage collection. The compiler assumes that all registers
+ * are still valid if a guard BIF generates an exception.
  */
 
 #define ERTS_NEED_GC(p, need) ((HEAP_LIMIT((p)) - HEAP_TOP((p))) <= (need))