From: Tom Tromey <tom@tromey.com>
Date: Sun, 29 Jul 2018 23:29:24 +0000 (-0600)
Subject: Avoid undefined behavior in read_subrange_type
X-Git-Url: https://git.libre-soc.org/?a=commitdiff_plain;h=d359392f976d48b04a27e6a09b5b61846b0727f9;p=binutils-gdb.git

Avoid undefined behavior in read_subrange_type

-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
2018-10-03  Tom Tromey  <tom@tromey.com>

	* dwarf2read.c (read_subrange_type): Make "negative_mask"
	unsigned.
---

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index 5787d44424f..4be30330e59 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,8 @@
+2018-10-03  Tom Tromey  <tom@tromey.com>
+
+	* dwarf2read.c (read_subrange_type): Make "negative_mask"
+	unsigned.
+
 2018-10-03  Tom Tromey  <tom@tromey.com>
 
 	* findvar.c (extract_integer): Do work in an unsigned type.
diff --git a/gdb/dwarf2read.c b/gdb/dwarf2read.c
index 4a35e389e93..4013c199dad 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;