Issue #7632: Fix one more case of incorrect rounding for str -> float
conversion (see bug 5 in the issue tracker).
diff --git a/Python/dtoa.c b/Python/dtoa.c
index 77117b9..aa577f2 100644
--- a/Python/dtoa.c
+++ b/Python/dtoa.c
@@ -1381,12 +1381,8 @@
goto ret;
}
s0 = s;
- y = z = 0;
for(nd = nf = 0; (c = *s) >= '0' && c <= '9'; nd++, s++)
- if (nd < 9)
- y = 10*y + c - '0';
- else if (nd < 16)
- z = 10*z + c - '0';
+ ;
nd0 = nd;
if (c == '.') {
c = *++s;
@@ -1406,15 +1402,7 @@
nz++;
if (c -= '0') {
nf += nz;
- for(i = 1; i < nz; i++)
- if (nd++ < 9)
- y *= 10;
- else if (nd <= DBL_DIG + 1)
- z *= 10;
- if (nd++ < 9)
- y = 10*y + c;
- else if (nd <= DBL_DIG + 1)
- z = 10*z + c;
+ nd += nz;
nz = 0;
}
}
@@ -1465,32 +1453,59 @@
}
goto ret;
}
- bc.e0 = e1 = e -= nf;
+ e -= nf;
+ if (!nd0)
+ nd0 = nd;
+
+ /* strip trailing zeros */
+ for (i = nd; i > 0; ) {
+ /* scan back until we hit a nonzero digit. significant digit 'i'
+ is s0[i] if i < nd0, s0[i+1] if i >= nd0. */
+ --i;
+ if (s0[i < nd0 ? i : i+1] != '0') {
+ ++i;
+ break;
+ }
+ }
+ e += nd - i;
+ nd = i;
+ if (nd0 > nd)
+ nd0 = nd;
/* Now we have nd0 digits, starting at s0, followed by a
* decimal point, followed by nd-nd0 digits. The number we're
* after is the integer represented by those digits times
* 10**e */
- if (!nd0)
- nd0 = nd;
+ bc.e0 = e1 = e;
/* Summary of parsing results. The parsing stage gives values
- * s0, nd0, nd, e, y and z such that:
+ * s0, nd0, nd, e, sign, where:
*
- * - nd >= nd0 >= 1
+ * - s0 points to the first significant digit of the input string s00;
*
- * - the nd significant digits are in s0[0:nd0] and s0[nd0+1:nd+1]
- * (using the usual Python half-open slice notation)
+ * - nd is the total number of significant digits (here, and
+ * below, 'significant digits' means the set of digits of the
+ * significand of the input that remain after ignoring leading
+ * and trailing zeros.
*
- * - the absolute value of the number represented by the original input
- * string is n * 10**e, where n is the integer represented by the
- * concatenation of s0[0:nd0] and s0[nd0+1:nd+1]
+ * - nd0 indicates the position of the decimal point (if
+ * present): so the nd significant digits are in s0[0:nd0] and
+ * s0[nd0+1:nd+1] using the usual Python half-open slice
+ * notation. (If nd0 < nd, then s0[nd0] necessarily contains
+ * a '.' character; if nd0 == nd, then it could be anything.)
*
- * - the first significant digit is nonzero
+ * - e is the adjusted exponent: the absolute value of the number
+ * represented by the original input string is n * 10**e, where
+ * n is the integer represented by the concatenation of
+ * s0[0:nd0] and s0[nd0+1:nd+1]
*
- * - the last significant digit may or may not be nonzero; (some code
- * currently assumes that it's nonzero; this is a bug)
+ * - sign gives the sign of the input: 1 for negative, 0 for positive
+ *
+ * - the first and last significant digits are nonzero
+ */
+
+ /* put first DBL_DIG+1 digits into integer y and z.
*
* - y contains the value represented by the first min(9, nd)
* significant digits
@@ -1500,6 +1515,16 @@
* gives the value represented by the first min(16, nd) sig. digits.
*/
+ y = z = 0;
+ for (i = 0; i < nd; i++) {
+ if (i < 9)
+ y = 10*y + s0[i < nd0 ? i : i+1] - '0';
+ else if (i < DBL_DIG+1)
+ z = 10*z + s0[i < nd0 ? i : i+1] - '0';
+ else
+ break;
+ }
+
k = nd < DBL_DIG + 1 ? nd : DBL_DIG + 1;
dval(&rv) = y;
if (k > 9) {