From dea306fe784789b0d9b7f63cd53f3b492d3a691d Mon Sep 17 00:00:00 2001
From: Paul Eggert <eggert@cs.ucla.edu>
Date: Wed, 7 Jun 2006 05:52:27 +0000
Subject: (integer_overflow): New function. (eval4, eval3): Check for integer
 overflow.

---
 src/expr.c | 38 +++++++++++++++++++++++++++++++++++---
 1 file changed, 35 insertions(+), 3 deletions(-)

diff --git a/src/expr.c b/src/expr.c
index c5b1ae87b..ab36350e5 100644
--- a/src/expr.c
+++ b/src/expr.c
@@ -175,6 +175,13 @@ syntax_error (void)
   error (EXPR_INVALID, 0, _("syntax error"));
 }
 
+/* Report an integer overflow for operation OP and exit.  */
+static void
+integer_overflow (char op)
+{
+  error (EXPR_FAILURE, ERANGE, "%c", op);
+}
+
 int
 main (int argc, char **argv)
 {
@@ -631,12 +638,26 @@ eval4 (bool evaluate)
 	  if (!toarith (l) || !toarith (r))
 	    error (EXPR_INVALID, 0, _("non-numeric argument"));
 	  if (fxn == multiply)
-	    val = l->u.i * r->u.i;
+	    {
+	      val = l->u.i * r->u.i;
+	      if (! (l->u.i == 0 || val / l->u.i == r->u.i))
+		integer_overflow ('*');
+	    }
 	  else
 	    {
 	      if (r->u.i == 0)
 		error (EXPR_INVALID, 0, _("division by zero"));
-	      val = fxn == divide ? l->u.i / r->u.i : l->u.i % r->u.i;
+	      if (l->u.i < - INTMAX_MAX && r->u.i == -1)
+		{
+		  /* Some x86-style hosts erroneously raise an
+		     exception for INT_MIN / -1 and INT_MIN % -1, so
+		     handle these problematic cases specially.  */
+		  if (fxn == divide)
+		    integer_overflow ('/');
+		  val = 0;
+		}
+	      else
+		val = fxn == divide ? l->u.i / r->u.i : l->u.i % r->u.i;
 	    }
 	}
       freev (l);
@@ -672,7 +693,18 @@ eval3 (bool evaluate)
 	{
 	  if (!toarith (l) || !toarith (r))
 	    error (EXPR_INVALID, 0, _("non-numeric argument"));
-	  val = fxn == plus ? l->u.i + r->u.i : l->u.i - r->u.i;
+	  if (fxn == plus)
+	    {
+	      val = l->u.i + r->u.i;
+	      if ((val < l->u.i) != (r->u.i < 0))
+		integer_overflow ('+');
+	    }
+	  else
+	    {
+	      val = l->u.i - r->u.i;
+	      if ((l->u.i < val) != (r->u.i < 0))
+		integer_overflow ('-');
+	    }
 	}
       freev (l);
       freev (r);
-- 
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