2008-08-23 James Youngman <[EMAIL PROTECTED]>
* find/parser.c (get_relative_timestamp): Check for overflow after
the fact by comparing the relatove sizes of the result and the
operands. This prevents an incorrect diagnosis of overflow when
the resulting tv_sec is correctly negative (as is normally the
case for -used).
---
find/parser.c | 30 +++++++++++++++++-------------
1 files changed, 17 insertions(+), 13 deletions(-)
diff --git a/find/parser.c b/find/parser.c
index 623b741..17db633 100644
--- a/find/parser.c
+++ b/find/parser.c
@@ -3233,9 +3233,9 @@ get_relative_timestamp (const char *str,
double sec_per_unit,
const char *overflowmessage)
{
- uintmax_t checkval;
double offset, seconds, nanosec;
-
+ static const long nanosec_per_sec = 1000000000;
+
if (get_comp_type(&str, &result->kind))
{
/* Invert the sense of the comparison */
@@ -3255,23 +3255,27 @@ get_relative_timestamp (const char *str,
*/
nanosec = modf(offset * sec_per_unit, &seconds);
nanosec *= 1.0e9; /* convert from fractional seconds to ns. */
-
+ assert (nanosec < nanosec_per_sec);
+
+ /* Perform the subtraction, and then check for overflow.
+ * On systems where signed aritmetic overflow does not
+ * wrap, this check may be unreliable. The C standard
+ * does not require this approach to work, but I am aware
+ * of no platforms where it fails.
+ */
result->ts.tv_sec = origin.tv_sec - seconds;
+ if ((origin.tv_sec < result->ts.tv_sec) != (seconds < 0))
+ {
+ /* an overflow has occurred. */
+ error (1, 0, overflowmessage, str);
+ }
+
result->ts.tv_nsec = origin.tv_nsec - nanosec;
- checkval = (uintmax_t)origin.tv_sec - seconds;
-
if (origin.tv_nsec < nanosec)
{
/* Perform a carry operation */
- result->ts.tv_nsec += 1000000000;
+ result->ts.tv_nsec += nanosec_per_sec;
result->ts.tv_sec -= 1;
- checkval -= 1;
- }
- /* Check for overflow. */
- if (checkval != result->ts.tv_sec)
- {
- /* an overflow has occurred. */
- error (1, 0, overflowmessage, str);
}
return true;
}
--
1.5.6.3
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