From: Mark Dickinson <dickinsm@gmail.com>
Date: Wed, 13 Jan 2010 19:02:37 +0000 (+0000)
Subject: Clarify that sulp expects a nonnegative input, but that +0.0 is fine.
X-Git-Tag: v2.7a3~164
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=5818e0125395b88b5e3c69dacdb50d5562628cd2;p=thirdparty%2FPython%2Fcpython.git

Clarify that sulp expects a nonnegative input, but that +0.0 is fine.
---

diff --git a/Python/dtoa.c b/Python/dtoa.c
index 504ad1f8cfff..e953f09c01e7 100644
--- a/Python/dtoa.c
+++ b/Python/dtoa.c
@@ -1130,11 +1130,11 @@ quorem(Bigint *b, Bigint *S)
     return q;
 }
 
-/* version of ulp(x) that takes bc.scale into account.
+/* sulp(x) is a version of ulp(x) that takes bc.scale into account.
 
-   Assuming that x is finite and nonzero, and x / 2^bc.scale is exactly
-   representable as a double, sulp(x) is equivalent to 2^bc.scale * ulp(x /
-   2^bc.scale). */
+   Assuming that x is finite and nonnegative (positive zero is fine
+   here) and x / 2^bc.scale is exactly representable as a double,
+   sulp(x) is equivalent to 2^bc.scale * ulp(x / 2^bc.scale). */
 
 static double
 sulp(U *x, BCinfo *bc)
@@ -1147,8 +1147,10 @@ sulp(U *x, BCinfo *bc)
         word1(&u) = 0;
         return u.d;
     }
-    else
+    else {
+        assert(word0(x) || word1(x)); /* x != 0.0 */
         return ulp(x);
+    }
 }
 
 /* The bigcomp function handles some hard cases for strtod, for inputs