Tidy check_uvalue

Alan Modra amodra@gmail.com
Wed Aug 28 23:33:00 GMT 2019


I don't see a need to calculate "ptr = start + uvalue" then compare
"ptr" with "start" and "end".  Given "start <= end" on entry, the
"uvalue" comparison with "max_uvalue" ought to be sufficient to ensure
"start + uvalue" is bounded by "start" and "end" regardless of the
size of pointers and the unsigned dwarf_vma integer type.

	* dwarf.c (check_uvalue): Remove unnecessary pointer checks.

diff --git a/binutils/dwarf.c b/binutils/dwarf.c
index 19ae1edca7..df924e4050 100644
--- a/binutils/dwarf.c
+++ b/binutils/dwarf.c
@@ -1848,16 +1848,9 @@ check_uvalue (const unsigned char * start,
 {
   dwarf_vma max_uvalue = end - start;
 
-  /* FIXME: Testing "(start + uvalue) < start" miscompiles with gcc 4.8.3
-     running on an x86_64 host in 32-bit mode.  So we pre-compute the value
-     here.  */
-  const unsigned char * ptr = start + uvalue;
-
   /* See PR 17512: file: 008-103549-0.001:0.1.
      and PR 24829 for examples of where these tests are triggered.  */
-  if (uvalue > max_uvalue
-      || ptr > end
-      || ptr < start)
+  if (uvalue > max_uvalue)
     {
       warn (_("Corrupt attribute block length: %lx\n"), (long) uvalue);
       uvalue = max_uvalue;

-- 
Alan Modra
Australia Development Lab, IBM



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