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

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Submitter Tom Tromey
Date Oct. 2, 2018, 4:44 a.m.
Message ID <20181002044420.17628-6-tom@tromey.com>
Download mbox | patch
Permalink /patch/29614/
State New
Headers show

Comments

Tom Tromey - Oct. 2, 2018, 4:44 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
2018-10-01  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(-)

Patch

diff --git a/gdb/dwarf2read.c b/gdb/dwarf2read.c
index 4a35e389e9..4013c199da 100644
--- a/gdb/dwarf2read.c
+++ b/gdb/dwarf2read.c
@@ -17709,7 +17709,7 @@  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,
@@ -17842,7 +17842,7 @@  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;