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Re: [PATCH] Handle bit-fields in ubsan.c (PR sanitizer/58413)

On Mon, Sep 16, 2013 at 06:04:23PM +0200, Jakub Jelinek wrote:
> On Mon, Sep 16, 2013 at 05:59:28PM +0200, Marek Polacek wrote:
> > Regtested/ran bootstrap-ubsan on x86_64-linux.
> That looks wrong.  ubsan_type_descriptor shouldn't change TYPE_PRECISION of
> the type it has been called with, whether type is a bitfield or not can
> change what typedescriptor is generated, but not unrelated code.

Ok, that was weird.  What about this one?  We use the TYPE_SIZE precision
if we're dealing with bit-fields, but don't change the type in any

Ubsan testsuite passes...

2013-09-16  Marek Polacek  <>

	PR sanitizer/58413
	* ubsan.c (get_ubsan_type_info_for_type): For bit-fields, use the
	precision of its TYPE_SIZE.

--- gcc/	2013-09-16 18:13:01.075903156 +0200
+++ gcc/ubsan.c	2013-09-16 18:13:20.514974154 +0200
@@ -233,7 +233,13 @@ ubsan_source_location (location_t loc)
 static unsigned short
 get_ubsan_type_info_for_type (tree type)
-  int prec = exact_log2 (TYPE_PRECISION (type));
+  int prec = TYPE_PRECISION (type);
+  /* Handle bit-fields.  */
+  if (compare_tree_int (TYPE_SIZE (type), prec) == 1)
+    prec = tree_low_cst (TYPE_SIZE (type), 1);
+  prec = exact_log2 (prec);
   if (prec == -1)
     error ("unexpected size of type %qT", type);


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