[v2,05/10] Avoid undefined behavior in read_subrange_type

Message ID 20180830024416.23386-6-tom@tromey.com
State Superseded
Headers show
Series
  • Enable undefined behavior sanitizer
Related show

Commit Message

Tom Tromey Aug. 30, 2018, 2:44 a.m.
-fsanitize=undefined pointed out an undefined shift of a negative
value in read_subrange_type.  The fix is to do the work in an unsigned
type, where this is defined.

gdb/ChangeLog
2018-08-29  Tom Tromey  <tom@tromey.com>

	* dwarf2read.c (read_subrange_type): Make "negative_mask"
	unsigned.
---
 gdb/ChangeLog    | 5 +++++
 gdb/dwarf2read.c | 4 ++--
 2 files changed, 7 insertions(+), 2 deletions(-)

-- 
2.13.6

Patch

diff --git a/gdb/dwarf2read.c b/gdb/dwarf2read.c
index 8834d08a1c6..86ef1c4040b 100644
--- a/gdb/dwarf2read.c
+++ b/gdb/dwarf2read.c
@@ -17682,7 +17682,7 @@  read_subrange_type (struct die_info *die, struct dwarf2_cu *cu)
   int low_default_is_valid;
   int high_bound_is_count = 0;
   const char *name;
-  LONGEST negative_mask;
+  ULONGEST negative_mask;
 
   orig_base_type = die_type (die, cu);
   /* If ORIG_BASE_TYPE is a typedef, it will not be TYPE_UNSIGNED,
@@ -17815,7 +17815,7 @@  read_subrange_type (struct die_info *die, struct dwarf2_cu *cu)
      the bounds as signed, and thus sign-extend their values, when
      the base type is signed.  */
   negative_mask =
-    -((LONGEST) 1 << (TYPE_LENGTH (base_type) * TARGET_CHAR_BIT - 1));
+    -((ULONGEST) 1 << (TYPE_LENGTH (base_type) * TARGET_CHAR_BIT - 1));
   if (low.kind == PROP_CONST
       && !TYPE_UNSIGNED (base_type) && (low.data.const_val & negative_mask))
     low.data.const_val |= negative_mask;