master a1f603f 2/3: Add overflow check for INPUT_EVENT_POS_MIN

[Paul Eggert]

branch: master
commit a1f603f0a388a519771ef77ae18f44a448a81c5a
Author: Paul Eggert <eggert@cs.ucla.edu>
Commit: Paul Eggert <eggert@cs.ucla.edu>

    Add overflow check for INPUT_EVENT_POS_MIN
    
    * src/keyboard.c (INPUT_EVENT_POS_MIN): Don’t assume (-1 -
    INPUT_EVENT_POS_MAX) fits into ptrdiff_t.  This fixes a
    purely-theoretical problem that cannot occur on two’s-complement
    arithmetic.  The Solaris 10 compiler still complains incorrectly,
    but oh well.
---
 src/keyboard.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/src/keyboard.c b/src/keyboard.c
index 0cf7ada..d2f0cb4 100644
--- a/src/keyboard.c
+++ b/src/keyboard.c
@@ -3647,7 +3647,8 @@ kbd_buffer_unget_event (struct selection_input_event 
*event)
 #define INPUT_EVENT_POS_MAX \
   ((ptrdiff_t) min (PTRDIFF_MAX, min (TYPE_MAXIMUM (Time) / 2, \
                                      MOST_POSITIVE_FIXNUM)))
-#define INPUT_EVENT_POS_MIN (-1 - INPUT_EVENT_POS_MAX)
+#define INPUT_EVENT_POS_MIN (PTRDIFF_MIN < -INPUT_EVENT_POS_MAX \
+                            ? -1 - INPUT_EVENT_POS_MAX : PTRDIFF_MIN)
 
 /* Return a Time that encodes position POS.  POS must be in range.  */