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.
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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.
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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.
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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.
........
diff --git a/Python/dtoa.c b/Python/dtoa.c
index 4f8bab7..1fe20f4 100644
--- a/Python/dtoa.c
+++ b/Python/dtoa.c
@@ -200,10 +200,11 @@
#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 @@
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 @@
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 @@
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 @@
}
}
- /* 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 @@
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 @@
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 @@
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 @@
/* 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 @@
/* accept rv */
break;
/* rv = smallest denormal */
- if (bc.nd >nd) {
- bc.uflchk = 1;
+ if (bc.nd >nd)
break;
- }
goto undfl;
}
}
@@ -1786,10 +1807,8 @@
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 @@
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.;