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Issue 7632: fix a dtoa.c bug (bug 6) causing incorrect rounding. Tests to follow.

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This commit is contained in:
Mark Dickinson 2010-01-14 13:14:49 +00:00
parent 03774fac62
commit 50b60c612e
1 changed files with 6 additions and 9 deletions
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15
Python/dtoa.c
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@ -1204,7 +1204,7 @@ static int
bigcomp(U *rv, const char *s0, BCinfo *bc) bigcomp(U *rv, const char *s0, BCinfo *bc)
{ {
Bigint *b, *d; Bigint *b, *d;
int b2, bbits, d2, dd, i, nd, nd0, p2, p5; int b2, bbits, d2, dd, i, nd, nd0, odd, p2, p5;
dd = 0; /* silence compiler warning about possibly unused variable */ dd = 0; /* silence compiler warning about possibly unused variable */
nd = bc->nd; nd = bc->nd;
@ -1237,6 +1237,9 @@ bigcomp(U *rv, const char *s0, BCinfo *bc)
b = lshift(b, ++i); b = lshift(b, ++i);
if (b == NULL) if (b == NULL)
return -1; return -1;
/* record whether the lsb of rv/2^(bc->scale) is odd: in the exact halfway
case, this is used for round to even. */
odd = b->x[0] & 2;
b->x[0] |= 1; b->x[0] |= 1;
p2 -= p5 + i; p2 -= p5 + i;
@ -1291,7 +1294,7 @@ bigcomp(U *rv, const char *s0, BCinfo *bc)
dd = -1; dd = -1;
goto ret; goto ret;
} }
/* Compare b/d with s0 */ /* Compare b/d with s0 */
for(i = 0; i < nd0; i++) { for(i = 0; i < nd0; i++) {
b = multadd(b, 10, 0); b = multadd(b, 10, 0);
@ -1329,14 +1332,8 @@ bigcomp(U *rv, const char *s0, BCinfo *bc)
ret: ret:
Bfree(b); Bfree(b);
Bfree(d); Bfree(d);
if (dd > 0) if (dd > 0 || (dd == 0 && odd))
dval(rv) += sulp(rv, bc); dval(rv) += sulp(rv, bc);
else if (dd == 0) {
/* Exact half-way case: apply round-even rule. */
if (word1(rv) & 1)
dval(rv) += sulp(rv, bc);
}
return 0; return 0;
} }