Merged revisions 77410,77421,77450-77451 via svnmerge from
svn+ssh://pythondev@svn.python.org/python/trunk ........ r77410 | mark.dickinson | 2010-01-10 13:06:31 +0000 (Sun, 10 Jan 2010) | 1 line Remove unused BCinfo fields and an unused macro. ........ r77421 | mark.dickinson | 2010-01-11 17:15:13 +0000 (Mon, 11 Jan 2010) | 1 line Change a variable type to avoid signed overflow; replace repeated '19999' constant by a define. ........ r77450 | mark.dickinson | 2010-01-12 22:23:56 +0000 (Tue, 12 Jan 2010) | 4 lines Issue #7632: Fix a problem with _Py_dg_strtod that could lead to crashes in debug builds, for certain long numeric strings corresponding to subnormal values. ........ r77451 | mark.dickinson | 2010-01-12 22:55:51 +0000 (Tue, 12 Jan 2010) | 2 lines Issue #7632: Fix a bug in dtoa.c that could lead to incorrectly-rounded results. ........
This commit is contained in:
Mark Dickinson
parent
f845302d06
commit
81612e8778
|
|
@ -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
|
||||
|
|
|
|||
|
|
@ -7,6 +7,7 @@ import math
|
|||
from math import isinf, isnan, copysign, ldexp
|
||||
import operator
|
||||
import random, fractions
|
||||
import re
|
||||
|
||||
INF = float("inf")
|
||||
NAN = float("nan")
|
||||
|
|
@ -20,6 +21,74 @@ requires_IEEE_754 = unittest.skipUnless(
|
|||
test_dir = os.path.dirname(__file__) or os.curdir
|
||||
format_testfile = os.path.join(test_dir, 'formatfloat_testcases.txt')
|
||||
|
||||
finite_decimal_parser = re.compile(r""" # A numeric string consists of:
|
||||
(?P<sign>[-+])? # an optional sign, followed by
|
||||
(?=\d|\.\d) # a number with at least one digit
|
||||
(?P<int>\d*) # having a (possibly empty) integer part
|
||||
(?:\.(?P<frac>\d*))? # followed by an optional fractional part
|
||||
(?:E(?P<exp>[-+]?\d+))? # and an optional exponent
|
||||
\Z
|
||||
""", re.VERBOSE | re.IGNORECASE | re.UNICODE).match
|
||||
|
||||
# Pure Python version of correctly rounded string->float conversion.
|
||||
# Avoids any use of floating-point by returning the result as a hex string.
|
||||
def strtod(s, mant_dig=53, min_exp = -1021, max_exp = 1024):
|
||||
"""Convert a finite decimal string to a hex string representing an
|
||||
IEEE 754 binary64 float. Return 'inf' or '-inf' on overflow.
|
||||
This function makes no use of floating-point arithmetic at any
|
||||
stage."""
|
||||
|
||||
# parse string into a pair of integers 'a' and 'b' such that
|
||||
# abs(decimal value) = a/b, and a boolean 'negative'.
|
||||
m = finite_decimal_parser(s)
|
||||
if m is None:
|
||||
raise ValueError('invalid numeric string')
|
||||
fraction = m.group('frac') or ''
|
||||
intpart = int(m.group('int') + fraction)
|
||||
exp = int(m.group('exp') or '0') - len(fraction)
|
||||
negative = m.group('sign') == '-'
|
||||
a, b = intpart*10**max(exp, 0), 10**max(0, -exp)
|
||||
|
||||
# quick return for zeros
|
||||
if not a:
|
||||
return '-0x0.0p+0' if negative else '0x0.0p+0'
|
||||
|
||||
# compute exponent e for result; may be one too small in the case
|
||||
# that the rounded value of a/b lies in a different binade from a/b
|
||||
d = a.bit_length() - b.bit_length()
|
||||
d += (a >> d if d >= 0 else a << -d) >= b
|
||||
e = max(d, min_exp) - mant_dig
|
||||
|
||||
# approximate a/b by number of the form q * 2**e; adjust e if necessary
|
||||
a, b = a << max(-e, 0), b << max(e, 0)
|
||||
q, r = divmod(a, b)
|
||||
if 2*r > b or 2*r == b and q & 1:
|
||||
q += 1
|
||||
if q.bit_length() == mant_dig+1:
|
||||
q //= 2
|
||||
e += 1
|
||||
|
||||
# double check that (q, e) has the right form
|
||||
assert q.bit_length() <= mant_dig and e >= min_exp - mant_dig
|
||||
assert q.bit_length() == mant_dig or e == min_exp - mant_dig
|
||||
|
||||
# check for overflow and underflow
|
||||
if e + q.bit_length() > max_exp:
|
||||
return '-inf' if negative else 'inf'
|
||||
if not q:
|
||||
return '-0x0.0p+0' if negative else '0x0.0p+0'
|
||||
|
||||
# for hex representation, shift so # bits after point is a multiple of 4
|
||||
hexdigs = 1 + (mant_dig-2)//4
|
||||
shift = 3 - (mant_dig-2)%4
|
||||
q, e = q << shift, e - shift
|
||||
return '{}0x{:x}.{:0{}x}p{:+d}'.format(
|
||||
'-' if negative else '',
|
||||
q // 16**hexdigs,
|
||||
q % 16**hexdigs,
|
||||
hexdigs,
|
||||
e + 4*hexdigs)
|
||||
|
||||
class GeneralFloatCases(unittest.TestCase):
|
||||
|
||||
def test_float(self):
|
||||
|
|
@ -1263,6 +1332,38 @@ class HexFloatTestCase(unittest.TestCase):
|
|||
else:
|
||||
self.identical(x, fromHex(toHex(x)))
|
||||
|
||||
class StrtodTestCase(unittest.TestCase):
|
||||
def check_string(self, s):
|
||||
expected = strtod(s)
|
||||
try:
|
||||
fs = float(s)
|
||||
except OverflowError:
|
||||
got = '-inf' if s[0] == '-' else 'inf'
|
||||
else:
|
||||
got = fs.hex()
|
||||
self.assertEqual(expected, got,
|
||||
"Incorrectly rounded str->float conversion for "
|
||||
"{}: expected {}, got {}".format(s, expected, got))
|
||||
|
||||
@unittest.skipUnless(getattr(sys, 'float_repr_style', '') == 'short',
|
||||
"applies only when using short float repr style")
|
||||
def test_bug7632(self):
|
||||
# check a few particular values that gave incorrectly rounded
|
||||
# results with previous versions of dtoa.c
|
||||
test_strings = [
|
||||
'94393431193180696942841837085033647913224148539854e-358',
|
||||
'12579816049008305546974391768996369464963024663104e-357',
|
||||
'17489628565202117263145367596028389348922981857013e-357',
|
||||
'18487398785991994634182916638542680759613590482273e-357',
|
||||
'32002864200581033134358724675198044527469366773928e-358',
|
||||
'73608278998966969345824653500136787876436005957953e-358',
|
||||
'64774478836417299491718435234611299336288082136054e-358',
|
||||
'13704940134126574534878641876947980878824688451169e-357',
|
||||
'46697445774047060960624497964425416610480524760471e-358',
|
||||
]
|
||||
for s in test_strings:
|
||||
self.check_string(s)
|
||||
|
||||
|
||||
def test_main():
|
||||
support.run_unittest(
|
||||
|
|
@ -1275,6 +1376,7 @@ def test_main():
|
|||
RoundTestCase,
|
||||
InfNanTest,
|
||||
HexFloatTestCase,
|
||||
StrtodTestCase,
|
||||
)
|
||||
|
||||
if __name__ == '__main__':
|
||||
|
|
|
|||
|
|
@ -12,6 +12,11 @@ What's New in Python 3.2 Alpha 1?
|
|||
Core and Builtins
|
||||
-----------------
|
||||
|
||||
- Issue #7632: Fix a crash in dtoa.c that occurred in debug builds
|
||||
when parsing certain long numeric strings corresponding to subnormal
|
||||
values. Also fix a number of bugs in dtoa.c that could lead to
|
||||
incorrectly rounded results when converting strings to floats.
|
||||
|
||||
- The __complex__ method is now looked up on the class of instances to make it
|
||||
consistent with other special methods.
|
||||
|
||||
|
|
|
|||
|
|
@ -200,10 +200,11 @@ typedef union { double d; ULong L[2]; } U;
|
|||
#define STRTOD_DIGLIM 40
|
||||
#endif
|
||||
|
||||
#ifdef DIGLIM_DEBUG
|
||||
extern int strtod_diglim;
|
||||
#else
|
||||
#define strtod_diglim STRTOD_DIGLIM
|
||||
/* maximum permitted exponent value for strtod; exponents larger than
|
||||
MAX_ABS_EXP in absolute value get truncated to +-MAX_ABS_EXP. MAX_ABS_EXP
|
||||
should fit into an int. */
|
||||
#ifndef MAX_ABS_EXP
|
||||
#define MAX_ABS_EXP 19999U
|
||||
#endif
|
||||
|
||||
/* The following definition of Storeinc is appropriate for MIPS processors.
|
||||
|
|
@ -269,8 +270,7 @@ extern int strtod_diglim;
|
|||
typedef struct BCinfo BCinfo;
|
||||
struct
|
||||
BCinfo {
|
||||
int dp0, dp1, dplen, dsign, e0, inexact;
|
||||
int nd, nd0, rounding, scale, uflchk;
|
||||
int dp0, dp1, dplen, dsign, e0, nd, nd0, scale;
|
||||
};
|
||||
|
||||
#define FFFFFFFF 0xffffffffUL
|
||||
|
|
@ -1130,6 +1130,26 @@ quorem(Bigint *b, Bigint *S)
|
|||
return q;
|
||||
}
|
||||
|
||||
/* 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). */
|
||||
|
||||
static double
|
||||
sulp(U *x, BCinfo *bc)
|
||||
{
|
||||
U u;
|
||||
|
||||
if (bc->scale && 2*P + 1 - ((word0(x) & Exp_mask) >> Exp_shift) > 0) {
|
||||
/* rv/2^bc->scale is subnormal */
|
||||
word0(&u) = (P+2)*Exp_msk1;
|
||||
word1(&u) = 0;
|
||||
return u.d;
|
||||
}
|
||||
else
|
||||
return ulp(x);
|
||||
}
|
||||
|
||||
/* return 0 on success, -1 on failure */
|
||||
|
||||
|
|
@ -1142,7 +1162,7 @@ bigcomp(U *rv, const char *s0, BCinfo *bc)
|
|||
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 +1247,21 @@ bigcomp(U *rv, const char *s0, BCinfo *bc)
|
|||
}
|
||||
}
|
||||
|
||||
/* 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 */
|
||||
/* 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 */
|
||||
|
||||
|
|
@ -1285,12 +1309,12 @@ bigcomp(U *rv, const char *s0, BCinfo *bc)
|
|||
else if (dd < 0) {
|
||||
if (!dsign) /* does not happen for round-near */
|
||||
retlow1:
|
||||
dval(rv) -= ulp(rv);
|
||||
dval(rv) -= sulp(rv, bc);
|
||||
}
|
||||
else if (dd > 0) {
|
||||
if (dsign) {
|
||||
rethi1:
|
||||
dval(rv) += ulp(rv);
|
||||
dval(rv) += sulp(rv, bc);
|
||||
}
|
||||
}
|
||||
else {
|
||||
|
|
@ -1312,13 +1336,12 @@ _Py_dg_strtod(const char *s00, char **se)
|
|||
int esign, i, j, k, nd, nd0, nf, nz, nz0, sign;
|
||||
const char *s, *s0, *s1;
|
||||
double aadj, aadj1;
|
||||
Long L;
|
||||
U aadj2, adj, rv, rv0;
|
||||
ULong y, z;
|
||||
ULong y, z, L;
|
||||
BCinfo bc;
|
||||
Bigint *bb, *bb1, *bd, *bd0, *bs, *delta;
|
||||
|
||||
sign = nz0 = nz = bc.dplen = bc.uflchk = 0;
|
||||
sign = nz0 = nz = bc.dplen = 0;
|
||||
dval(&rv) = 0.;
|
||||
for(s = s00;;s++) switch(*s) {
|
||||
case '-':
|
||||
|
|
@ -1413,11 +1436,11 @@ _Py_dg_strtod(const char *s00, char **se)
|
|||
s1 = s;
|
||||
while((c = *++s) >= '0' && c <= '9')
|
||||
L = 10*L + c - '0';
|
||||
if (s - s1 > 8 || L > 19999)
|
||||
if (s - s1 > 8 || L > MAX_ABS_EXP)
|
||||
/* Avoid confusion from exponents
|
||||
* so large that e might overflow.
|
||||
*/
|
||||
e = 19999; /* safe for 16 bit ints */
|
||||
e = (int)MAX_ABS_EXP; /* safe for 16 bit ints */
|
||||
else
|
||||
e = (int)L;
|
||||
if (esign)
|
||||
|
|
@ -1555,11 +1578,11 @@ _Py_dg_strtod(const char *s00, char **se)
|
|||
/* Put digits into bd: true value = bd * 10^e */
|
||||
|
||||
bc.nd = nd;
|
||||
bc.nd0 = nd0; /* Only needed if nd > strtod_diglim, but done here */
|
||||
bc.nd0 = nd0; /* Only needed if nd > STRTOD_DIGLIM, but done here */
|
||||
/* to silence an erroneous warning about bc.nd0 */
|
||||
/* possibly not being initialized. */
|
||||
if (nd > strtod_diglim) {
|
||||
/* ASSERT(strtod_diglim >= 18); 18 == one more than the */
|
||||
if (nd > STRTOD_DIGLIM) {
|
||||
/* ASSERT(STRTOD_DIGLIM >= 18); 18 == one more than the */
|
||||
/* minimum number of decimal digits to distinguish double values */
|
||||
/* in IEEE arithmetic. */
|
||||
i = j = 18;
|
||||
|
|
@ -1767,10 +1790,8 @@ _Py_dg_strtod(const char *s00, char **se)
|
|||
/* accept rv */
|
||||
break;
|
||||
/* rv = smallest denormal */
|
||||
if (bc.nd >nd) {
|
||||
bc.uflchk = 1;
|
||||
if (bc.nd >nd)
|
||||
break;
|
||||
}
|
||||
goto undfl;
|
||||
}
|
||||
}
|
||||
|
|
@ -1786,10 +1807,8 @@ _Py_dg_strtod(const char *s00, char **se)
|
|||
else {
|
||||
dval(&rv) -= ulp(&rv);
|
||||
if (!dval(&rv)) {
|
||||
if (bc.nd >nd) {
|
||||
bc.uflchk = 1;
|
||||
if (bc.nd >nd)
|
||||
break;
|
||||
}
|
||||
goto undfl;
|
||||
}
|
||||
}
|
||||
|
|
@ -1801,10 +1820,8 @@ _Py_dg_strtod(const char *s00, char **se)
|
|||
aadj = aadj1 = 1.;
|
||||
else if (word1(&rv) || word0(&rv) & Bndry_mask) {
|
||||
if (word1(&rv) == Tiny1 && !word0(&rv)) {
|
||||
if (bc.nd >nd) {
|
||||
bc.uflchk = 1;
|
||||
if (bc.nd >nd)
|
||||
break;
|
||||
}
|
||||
goto undfl;
|
||||
}
|
||||
aadj = 1.;
|
||||
|
|
|
|||
Loading…
Reference in New Issue