From 7690cbb0f9d9f7bb56edd67c06a89f116dd4f80d Mon Sep 17 00:00:00 2001
From: "Richard M. Stallman" <rms@gnu.org>
Date: Sat, 25 Jun 2005 04:31:49 +0000
Subject: [PATCH] (read1): 0.0e+NaN should make a "positive" NaN.

---
 src/lread.c | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/src/lread.c b/src/lread.c
index 9317933013e..ccc94c32dd1 100644
--- a/src/lread.c
+++ b/src/lread.c
@@ -2595,6 +2595,23 @@ read1 (readcharfun, pch, first_in_list)
 		    break;
 		  case 'N':
 		    value = zero / zero;
+
+		    /* If that made a "negative" NaN, negate it.  */
+
+		    {
+		      int i;
+		      union { double d; char c[sizeof (double)]; } u_data, u_minus_zero;
+
+		      u_data.d = value;
+		      u_minus_zero.d = - 0.0;
+		      for (i = 0; i < sizeof (double); i++)
+			if (u_data.c[i] & u_minus_zero.c[i])
+			  {
+			    value = - value;
+			    break;
+			  }
+		    }
+		    /* Now VALUE is a positive NaN.  */
 		    break;
 		  default:
 		    value = atof (read_buffer + negative);
-- 
2.39.2