Fix code which depends on signed overflow in C (which isn't defined in C)

[mc-butler]

Important

This issue was migrated from Trac:

Origin	https://midnight-commander.org/ticket/2989
Reporter	vda (@dvlasenk)

The warnings are:

src/vfs/smbfs/helpers/lib/time.c:177:16: warning: assuming signed overflow does not occur when assuming that (X - c) > X is always false [-Wstrict-overflow]
src/vfs/smbfs/helpers/lib/time.c:181:16: warning: assuming signed overflow does not occur when assuming that (X + c) < X is always false [-Wstrict-overflow]

and they seems to be valid, and gcc people do intend to make gcc play tricks under "signed overflow is undefined, so we can assume it never happens" banner.

The patch was sent by email with subject line
"Fix code which depends on signed overflow in C (which isn't defined in C)".
For your easy reference, it is just:

             /* no entry will cover more than 6 months */
-            low = t - MAX_DST_WIDTH / 2;
-            if (t < low)
+            if (t > TIME_T_MIN + MAX_DST_WIDTH / 2)
+                low = t - MAX_DST_WIDTH / 2;
+            else
                 low = TIME_T_MIN;

-            high = t + MAX_DST_WIDTH / 2;
-            if (high < t)
+            if (t < TIME_T_MAX - MAX_DST_WIDTH / 2)
+                high = t + MAX_DST_WIDTH / 2;
+            else
                 high = TIME_T_MAX;

[mc-butler]

Changed by andrew_b (@aborodin) on Aug 31, 2013 at 8:27 UTC (comment 1)

• Component changed from mc-core to mc-vfs

[mc-butler]

Changed by andrew_b (@aborodin) on Apr 5, 2015 at 7:03 UTC (comment 2)

• Status changed from new to closed
• Milestone Future Releases deleted
• Resolution set to wontfix

Samba code used in mc is ancient and should be rewritten totally (see #1).