From: Michaël Cadilhac <michael.cadilhac@lrde.org>
Date: Mon, 1 Oct 2007 09:17:29 +0000 (+0000)
Subject: (Fexpt): Manually check for overflows, so that a power
X-Git-Tag: emacs-pretest-23.0.90~10559
X-Git-Url: http://git.eshelyaron.com/gitweb/?a=commitdiff_plain;h=2742fe306859d828cbeff3ae0371e2217b09cd4c;p=emacs.git

(Fexpt): Manually check for overflows, so that a power
of a non-zero value can't yield zero.
---

diff --git a/src/ChangeLog b/src/ChangeLog
index 70fbaad280e..e71218880bc 100644
--- a/src/ChangeLog
+++ b/src/ChangeLog
@@ -1,3 +1,8 @@
+2007-10-01  Micha,Ak(Bl Cadilhac  <michael@cadilhac.name>
+
+	* floatfns.c (Fexpt): Manually check for overflows, so that a power
+	of a non-zero value can't yield zero.
+
 2007-09-29  Stefan Monnier  <monnier@iro.umontreal.ca>
 
 	* term.c (term_clear_mouse_face, term_mouse_highlight)
diff --git a/src/floatfns.c b/src/floatfns.c
index 6ad9b95686e..a20f7981bf0 100644
--- a/src/floatfns.c
+++ b/src/floatfns.c
@@ -454,7 +454,7 @@ DEFUN ("expt", Fexpt, Sexpt, 2, 2, 0,
      (arg1, arg2)
      register Lisp_Object arg1, arg2;
 {
-  double f1, f2;
+  double f1, f2, f3;
 
   CHECK_NUMBER_OR_FLOAT (arg1);
   CHECK_NUMBER_OR_FLOAT (arg2);
@@ -500,8 +500,11 @@ DEFUN ("expt", Fexpt, Sexpt, 2, 2, 0,
   else if ((f1 == 0.0 && f2 < 0.0) || (f1 < 0 && f2 != floor(f2)))
     domain_error2 ("expt", arg1, arg2);
 #endif
-  IN_FLOAT2 (f1 = pow (f1, f2), "expt", arg1, arg2);
-  return make_float (f1);
+  IN_FLOAT2 (f3 = pow (f1, f2), "expt", arg1, arg2);
+  /* Check for overflow in the result.  */
+  if (f1 != 0.0 && f3 == 0.0)
+    range_error ("expt", arg1);
+  return make_float (f3);
 }
 
 DEFUN ("log", Flog, Slog, 1, 2, 0,