Index: Python/dtoa.c
===================================================================
--- Python/dtoa.c	(revision 77361)
+++ Python/dtoa.c	(working copy)
@@ -1142,7 +1142,7 @@
 dsign = bc->dsign;
 nd = bc->nd;
 nd0 = bc->nd0;
- p5 = nd + bc->e0 - 1;
+ p5 = nd + bc->e0;
 speccase = 0;
 if (rv->d == 0.) { /* special case: value near underflow-to-zero */
 /* threshold was rounded to zero */
@@ -1227,17 +1227,21 @@
 }
 }
 
- /* Now b/d = exactly half-way between the two floating-point values */
- /* on either side of the input string. Compute first digit of b/d. */
+ /* Now 10*b/d = exactly half-way between the two floating-point values */
+ /* on either side of the input string. If b>= d, round down. */
+ if (cmp(b, d)>= 0) {
+ dd = -1;
+ goto ret;
+ }
 
- if (!(dig = quorem(b,d))) {
- b = multadd(b, 10, 0); /* very unlikely */
- if (b == NULL) {
- Bfree(d);
- return -1;
- }
- dig = quorem(b,d);
+ /* Compute first digit of 10*b/d. */
+ b = multadd(b, 10, 0);
+ if (b == NULL) {
+ Bfree(d);
+ return -1;
 }
+ dig = quorem(b, d);
+ assert(dig < 10); /* Compare b/d with s0 */ Index: Lib/test/floating_points.txt =================================================================== --- Lib/test/floating_points.txt (revision 77361) +++ Lib/test/floating_points.txt (working copy) @@ -1019,3 +1019,10 @@ +43723334984997307E-26 +10182419849537963E-24 -93501703572661982E-26 + +# A value that caused a crash in debug builds for Python>= 2.7, 3.1
+# See http://bugs.python.org/issue7632
+2183167012312112312312.23538020374420446192e-370
+
+# Another value designed to test a corner case of Python's strtod code.
+0.99999999999999999999999999999999999999999e+23
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