float_divmod(): the code wasn't sick enough to stop the MS optimizer

tim-one · tim-one · commit 4e8ab5db38c8 · 2001-11-01T23:59:56.000Z
from optimizing away mod's sign adjustment when mod == 0; so it got
the intended result only in the debug build.
diff --git a/Objects/floatobject.c b/Objects/floatobject.c
@@ -476,7 +476,7 @@ float_divmod(PyObject *v, PyObject *w)
 		   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;
+		mod *= mod;  /* hide "mod = +0" from optimizer */
 		if (wx < 0.0)
 			mod = -mod;
 	}

Original file line number	Diff line number	Diff line change
`@@ -476,7 +476,7 @@ float_divmod(PyObject v, PyObject w)`
`476`	`476`	`fmod returns different results across platforms; ensure`
`477`	`477`	`it has the same sign as the denominator; we'd like to do`
`478`	`478`	`"mod = wx * 0.0", but that may get optimized away */`
`479`		`- mod = 0.0;`
	`479`	`+ mod = mod; / hide "mod = +0" from optimizer */`
`480`	`480`	`if (wx < 0.0)`
`481`	`481`	`mod = -mod;`
`482`	`482`	`}`