# HG changeset patch
# User Jerry James <james@xemacs.org>
# Date 1267562557 25200
# Node ID 207dad9e74f79373e58cbb863ae56f03a237dd8d
# Parent  818eeb72e0fbed6b97b7da770416f7340838e3eb
Signal an error upon reading 1/0.
Thanks to Ben Wing for finding the problem.  See xemacs-patches message with ID
<870180fe1003021239k77d81203xb7b6f94ce83208b3@mail.gmail.com> and also
<d7ba68911002240223u36bb87c2nf4ccfde06b5519cc@mail.gmail.com> in xemacs-beta.

diff -r 818eeb72e0fb -r 207dad9e74f7 src/ChangeLog
--- a/src/ChangeLog	Tue Mar 02 13:25:45 2010 -0700
+++ b/src/ChangeLog	Tue Mar 02 13:42:37 2010 -0700
@@ -1,3 +1,8 @@
+2010-03-02  Jerry James  <james@xemacs.org>
+
+	* lread.c (read_atom): Signal a read error upon encountering a
+	ratio constant with a zero denominator.
+
 2010-03-02  Aidan Kehoe  <kehoea@parhasard.net>
 
 	* eval.c (print_multiple_value):
diff -r 818eeb72e0fb -r 207dad9e74f7 src/lread.c
--- a/src/lread.c	Tue Mar 02 13:25:45 2010 -0700
+++ b/src/lread.c	Tue Mar 02 13:42:37 2010 -0700
@@ -1982,8 +1982,14 @@
 	  if (*read_ptr == '+')
 	    read_ptr++;
 	  ratio_set_string (scratch_ratio, read_ptr, 0);
-	  ratio_canonicalize (scratch_ratio);
-	  return Fcanonicalize_number (make_ratio_rt (scratch_ratio));
+	  if (bignum_sign (ratio_denominator (scratch_ratio)) != 0) {
+	    ratio_canonicalize (scratch_ratio);
+	    return Fcanonicalize_number (make_ratio_rt (scratch_ratio));
+	  }
+	  return Fsignal (Qinvalid_read_syntax,
+			  list2 (build_msg_string
+				 ("Invalid ratio constant in reader"),
+				 make_string ((Ibyte *) read_ptr, len)));
 	}
 #endif
       if (isfloat_string (read_ptr))