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Merged revisions 77452 via svnmerge from

Browse source 
svn+ssh://pythondev@svn.python.org/python/branches/py3k

................
  r77452 | mark.dickinson | 2010-01-12 23:04:19 +0000 (Tue, 12 Jan 2010) | 23 lines

  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.
  ........
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This commit is contained in:
Mark Dickinson 2010-01-12 23:09:26 +00:00
parent d7966fca12
commit 466725136d
4 changed files with 167 additions and 36 deletions
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89
Python/dtoa.c
View file

@ -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. */
if (!(dig = quorem(b,d))) {
b = multadd(b, 10, 0); /* very unlikely */
if (b == NULL) {
Bfree(d);
return -1;
}
dig = quorem(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;
}
/* 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.;