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[binutils-gdb] Avoid undefined behavior in extract_integer
- From: Tom Tromey <tromey at sourceware dot org>
- To: gdb-cvs at sourceware dot org
- Date: 3 Oct 2018 21:28:32 -0000
- Subject: [binutils-gdb] Avoid undefined behavior in extract_integer
https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=0101665f864383147448c5871a67286a3f7a9a28
commit 0101665f864383147448c5871a67286a3f7a9a28
Author: Tom Tromey <tom@tromey.com>
Date: Sun Jul 29 17:16:03 2018 -0600
Avoid undefined behavior in extract_integer
-fsanitize=undefined showed that extract_integer could left-shift a
negative value, which is undefined. This patch fixes the problem by
doing all the work in an unsigned type. This relies on
implementation-defined behavior, but I tend to think we are on safe
ground there. (Also, if need be, violations of this could probably be
detected, either by configure or by a static_assert.)
gdb/ChangeLog
2018-10-03 Tom Tromey <tom@tromey.com>
* findvar.c (extract_integer): Do work in an unsigned type.
Diff:
---
gdb/ChangeLog | 4 ++++
gdb/findvar.c | 2 +-
2 files changed, 5 insertions(+), 1 deletion(-)
diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index 36c4493..5787d44 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,5 +1,9 @@
2018-10-03 Tom Tromey <tom@tromey.com>
+ * findvar.c (extract_integer): Do work in an unsigned type.
+
+2018-10-03 Tom Tromey <tom@tromey.com>
+
* common/enum-flags.h (enum_flags::operator~): Add static assert.
* symfile-add-flags.h (enum symfile_add_flag): Use unsigned as
base type.
diff --git a/gdb/findvar.c b/gdb/findvar.c
index 9256833..be6c9d6 100644
--- a/gdb/findvar.c
+++ b/gdb/findvar.c
@@ -50,7 +50,7 @@ template<typename T, typename>
T
extract_integer (const gdb_byte *addr, int len, enum bfd_endian byte_order)
{
- T retval = 0;
+ typename std::make_unsigned<T>::type retval = 0;
const unsigned char *p;
const unsigned char *startaddr = addr;
const unsigned char *endaddr = startaddr + len;