From: Paul Eggert <eggert@cs.ucla.edu>
Date: Fri, 1 Jan 2021 20:55:35 +0000 (-0800)
Subject: Add overflow check for INPUT_EVENT_POS_MIN
X-Git-Tag: emacs-28.0.90~4435
X-Git-Url: http://git.eshelyaron.com/gitweb/?a=commitdiff_plain;h=a1f603f0a388a519771ef77ae18f44a448a81c5a;p=emacs.git

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.
---

diff --git a/src/keyboard.c b/src/keyboard.c
index 0cf7adae741..d2f0cb405f0 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.  */