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[binutils-gdb] Avoid undefined behavior in read_signed_leb128
- From: Tom Tromey <tromey at sourceware dot org>
- To: gdb-cvs at sourceware dot org
- Date: 3 Oct 2018 21:28:52 -0000
- Subject: [binutils-gdb] Avoid undefined behavior in read_signed_leb128
https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=4dd1b46077b2ae7331f274f7888733de5166445c
commit 4dd1b46077b2ae7331f274f7888733de5166445c
Author: Tom Tromey <tom@tromey.com>
Date: Fri Aug 17 20:19:13 2018 -0600
Avoid undefined behavior in read_signed_leb128
-fsanitize=undefined pointed out that read_signed_leb128 had an
undefined left-shift when processing the final byte of a 64-bit leb:
runtime error: left shift of 127 by 63 places cannot be represented in type 'long int'
and an undefined negation:
runtime error: negation of -9223372036854775808 cannot be represented in type 'long int'; cast to an unsigned type to negate this value to itself
Both of these problems are readily avoided by havinng
read_signed_leb128 work in an unsigned type, and then casting to the
signed type at the return.
gdb/ChangeLog
2018-10-03 Tom Tromey <tom@tromey.com>
* dwarf2read.c (read_signed_leb128): Work in ULONGEST.
Diff:
---
gdb/ChangeLog | 4 ++++
gdb/dwarf2read.c | 6 +++---
2 files changed, 7 insertions(+), 3 deletions(-)
diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index 97ee73b..9731c99 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,5 +1,9 @@
2018-10-03 Tom Tromey <tom@tromey.com>
+ * dwarf2read.c (read_signed_leb128): Work in ULONGEST.
+
+2018-10-03 Tom Tromey <tom@tromey.com>
+
* c-exp.y (parse_number): Work in unsigned. Remove casts.
2018-10-03 Tom Tromey <tom@tromey.com>
diff --git a/gdb/dwarf2read.c b/gdb/dwarf2read.c
index 4013c19..7004299 100644
--- a/gdb/dwarf2read.c
+++ b/gdb/dwarf2read.c
@@ -19627,7 +19627,7 @@ static LONGEST
read_signed_leb128 (bfd *abfd, const gdb_byte *buf,
unsigned int *bytes_read_ptr)
{
- LONGEST result;
+ ULONGEST result;
int shift, num_read;
unsigned char byte;
@@ -19639,7 +19639,7 @@ read_signed_leb128 (bfd *abfd, const gdb_byte *buf,
byte = bfd_get_8 (abfd, buf);
buf++;
num_read++;
- result |= ((LONGEST) (byte & 127) << shift);
+ result |= ((ULONGEST) (byte & 127) << shift);
shift += 7;
if ((byte & 128) == 0)
{
@@ -19647,7 +19647,7 @@ read_signed_leb128 (bfd *abfd, const gdb_byte *buf,
}
}
if ((shift < 8 * sizeof (result)) && (byte & 0x40))
- result |= -(((LONGEST) 1) << shift);
+ result |= -(((ULONGEST) 1) << shift);
*bytes_read_ptr = num_read;
return result;
}