From 20562150d8a894bc91657c843ee88c508188e32e Mon Sep 17 00:00:00 2001 From: Tom Tromey Date: Sun, 29 Jul 2018 20:23:33 -0600 Subject: [PATCH] Avoid undefined behavior in parse_number -fsanitize=undefined pointed out that c-exp.y relied on undefined behavior here: if (c != 'l' && c != 'u') n *= base; ...when a large hex constant "just fit" into a LONGEST, causing the high bit to be set. This fixes the problem by having the function work in an unsigned type. gdb/ChangeLog 2018-10-03 Tom Tromey * c-exp.y (parse_number): Work in unsigned. Remove casts. --- gdb/ChangeLog | 4 ++++ gdb/c-exp.y | 10 ++++------ 2 files changed, 8 insertions(+), 6 deletions(-) diff --git a/gdb/ChangeLog b/gdb/ChangeLog index 4be30330e59..97ee73bab38 100644 --- a/gdb/ChangeLog +++ b/gdb/ChangeLog @@ -1,3 +1,7 @@ +2018-10-03 Tom Tromey + + * c-exp.y (parse_number): Work in unsigned. Remove casts. + 2018-10-03 Tom Tromey * dwarf2read.c (read_subrange_type): Make "negative_mask" diff --git a/gdb/c-exp.y b/gdb/c-exp.y index 0326ee090e1..09e31d2283a 100644 --- a/gdb/c-exp.y +++ b/gdb/c-exp.y @@ -1760,10 +1760,8 @@ static int parse_number (struct parser_state *par_state, const char *buf, int len, int parsed_float, YYSTYPE *putithere) { - /* FIXME: Shouldn't these be unsigned? We don't deal with negative values - here, and we do kind of silly things like cast to unsigned. */ - LONGEST n = 0; - LONGEST prevn = 0; + ULONGEST n = 0; + ULONGEST prevn = 0; ULONGEST un; int i = 0; @@ -1922,7 +1920,7 @@ parse_number (struct parser_state *par_state, on 0x123456789 when LONGEST is 32 bits. */ if (c != 'l' && c != 'u' && n != 0) { - if ((unsigned_p && (ULONGEST) prevn >= (ULONGEST) n)) + if (unsigned_p && prevn >= n) error (_("Numeric constant too large.")); } prevn = n; @@ -1940,7 +1938,7 @@ parse_number (struct parser_state *par_state, the case where it is we just always shift the value more than once, with fewer bits each time. */ - un = (ULONGEST)n >> 2; + un = n >> 2; if (long_p == 0 && (un >> (gdbarch_int_bit (parse_gdbarch (par_state)) - 2)) == 0) { -- 2.30.2