From 4dd1b46077b2ae7331f274f7888733de5166445c Mon Sep 17 00:00:00 2001 From: Tom Tromey Date: Fri, 17 Aug 2018 20:19:13 -0600 Subject: [PATCH] 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 * dwarf2read.c (read_signed_leb128): Work in ULONGEST. --- gdb/ChangeLog | 4 ++++ gdb/dwarf2read.c | 6 +++--- 2 files changed, 7 insertions(+), 3 deletions(-) diff --git a/gdb/ChangeLog b/gdb/ChangeLog index 97ee73bab3..9731c99a6a 100644 --- a/gdb/ChangeLog +++ b/gdb/ChangeLog @@ -1,3 +1,7 @@ +2018-10-03 Tom Tromey + + * dwarf2read.c (read_signed_leb128): Work in ULONGEST. + 2018-10-03 Tom Tromey * c-exp.y (parse_number): Work in unsigned. Remove casts. diff --git a/gdb/dwarf2read.c b/gdb/dwarf2read.c index 4013c199da..7004299a91 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; } -- 2.34.1