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authorTom Tromey <tom@tromey.com>2018-07-29 20:23:33 -0600
committerTom Tromey <tom@tromey.com>2018-10-03 15:19:06 -0600
commit20562150d8a894bc91657c843ee88c508188e32e (patch)
treeb211b0f74e83b41e417b21e6e9faa905b49acc4e /gdb/c-exp.y
parentd359392f976d48b04a27e6a09b5b61846b0727f9 (diff)
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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 <tom@tromey.com> * c-exp.y (parse_number): Work in unsigned. Remove casts.
Diffstat (limited to 'gdb/c-exp.y')
-rw-r--r--gdb/c-exp.y10
1 files changed, 4 insertions, 6 deletions
diff --git a/gdb/c-exp.y b/gdb/c-exp.y
index 0326ee0..09e31d2 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)
{