[Python-checkins] CVS: python/dist/src/Objects floatobject.c,2.104,2.105

2001年11月01日 15:12:29 -0800

Update of /cvsroot/python/python/dist/src/Objects
In directory usw-pr-cvs1:/tmp/cvs-serv12223/python/Objects
Modified Files:
	floatobject.c 
Log Message:
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.
Index: floatobject.c
===================================================================
RCS file: /cvsroot/python/python/dist/src/Objects/floatobject.c,v
retrieving revision 2.104
retrieving revision 2.105
diff -C2 -d -r2.104 -r2.105
*** floatobject.c	2001年11月01日 21:51:15	2.104
--- floatobject.c	2001年11月01日 23:12:27	2.105
***************
*** 465,479 ****
 	*/
 	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;
 	}
 	/* snap quotient to nearest integral value */
! 	floordiv = floor(div);
! 	if (div - floordiv > 0.5)
! 		floordiv += 1.0;
! 	PyFPE_END_PROTECT(div)
 	return Py_BuildValue("(dd)", floordiv, mod);
 }
--- 465,496 ----
 	*/
 	div = (vx - mod) / wx;
! 	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 */
! 	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);
 }