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SF bug #477221: abs and divmod act oddly with -0.0 

Try to ensure that divmod(-0.0, 1.0) -> (-0.0, +0.0) across platforms.
It always did on Windows, and still does.  It didn't on Linux.  Alas,
there's no platform-independent way to write a test case for this.
Bugfix candidate.
This commit is contained in:
Tim Peters 2001-11-01 23:12:27 +00:00
parent faf0cd21ed
commit d2e40d6691
1 changed files with 26 additions and 9 deletions
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35
Objects/floatobject.c
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@ -464,17 +464,34 @@ float_divmod(PyObject *v, PyObject *w)
it will always be very close to one.
*/
div = (vx - mod) / wx;
/* note: checking mod*wx < 0 is incorrect -- underflows to
0 if wx < sqrt(smallest nonzero double) */
if (mod && ((wx < 0) != (mod < 0))) {
mod += wx;
div -= 1.0;
if (mod) {
/* ensure the remainder has the same sign as the denominator */
if ((wx < 0) != (mod < 0)) {
mod += wx;
div -= 1.0;
}
}
else {
/* the remainder is zero, and in the presence of signed zeroes
fmod returns different results across platforms; ensure
it has the same sign as the denominator; we'd like to do
"mod = wx * 0.0", but that may get optimized away */
mod = 0.0;
if (wx < 0.0)
mod = -mod;
}
/* snap quotient to nearest integral value */
floordiv = floor(div);
if (div - floordiv > 0.5)
floordiv += 1.0;
PyFPE_END_PROTECT(div)
if (div) {
floordiv = floor(div);
if (div - floordiv > 0.5)
floordiv += 1.0;
}
else {
/* div is zero - get the same sign as the true quotient */
div *= div; /* hide "div = +0" from optimizers */
floordiv = div * vx / wx; /* zero w/ sign of vx/wx */
}
PyFPE_END_PROTECT(floordiv)
return Py_BuildValue("(dd)", floordiv, mod);
}