bug#11712: 24.1.50; systime.h shouldn't cast time_t values to long

[Ulrich Mueller]

The EMACS_TIME_CMP macro defined in systime.h casts the seconds values
(which are of type time_t) to long. This is problematic on platforms
where time_t has 64 bits but long has only 32 bits, for example
GNU/Linux x64_64 systems with x32 ABI.

Attached patch should fix it.

--- emacs-orig/src/ChangeLog
+++ emacs/src/ChangeLog
@@ -1,3 +1,7 @@
+2012-06-14  Ulrich Müller  <ulm@gentoo.org>
+
+       * systime.h (EMACS_TIME_CMP): Don't cast time_t values to long.
+
 2012-06-14  Paul Eggert  <eggert@cs.ucla.edu>
 
        * .gdbinit (xgetint): Fix recently-introduced paren typo.
--- emacs-orig/src/systime.h
+++ emacs/src/systime.h
@@ -147,15 +147,12 @@
 #endif
 
 /* Compare times T1 and T2.  Value is 0 if T1 and T2 are the same.
-   Value is < 0 if T1 is less than T2.  Value is > 0 otherwise.  (Cast
-   to long is for those platforms where time_t is an unsigned
-   type, and where otherwise T1 will always be grater than T2.)  */
+   Value is < 0 if T1 is less than T2.  Value is > 0 otherwise.  */
 
 #define EMACS_TIME_CMP(T1, T2)                         \
-  ((long)EMACS_SECS (T1) - (long)EMACS_SECS (T2)       \
-   + (EMACS_SECS (T1) == EMACS_SECS (T2)               \
-      ? EMACS_USECS (T1) - EMACS_USECS (T2)            \
-      : 0))
+  (EMACS_SECS (T1) == EMACS_SECS (T2)                  \
+   ? EMACS_USECS (T1) - EMACS_USECS (T2)               \
+   : (EMACS_SECS (T1) < EMACS_SECS (T2) ? -1 : 1))
 
 /* Compare times T1 and T2 for equality, inequality etc.  */