New try to fix test_time.test_AsSecondsDouble() on x86 buildbots.

vstinner · vstinner · commit ff0ed3e71cb8 · 2015-09-10T13:25:17.000+02:00
Use volatile keyword in _PyTime_AsSecondsDouble()
diff --git a/Python/pytime.c b/Python/pytime.c
@@ -332,16 +332,21 @@ _PyTime_FromMillisecondsObject(_PyTime_t *t, PyObject *obj, _PyTime_round_t roun
 double
 _PyTime_AsSecondsDouble(_PyTime_t t)
 {
+    /* volatile avoids optimization changing how numbers are rounded */
+    volatile double d;
+
     if (t % SEC_TO_NS == 0) {
         _PyTime_t secs;
         /* Divide using integers to avoid rounding issues on the integer part.
            1e-9 cannot be stored exactly in IEEE 64-bit. */
         secs = t / SEC_TO_NS;
-        return (double)secs;
+        d = (double)secs;
     }
     else {
-        return (double)t / 1e9;
+        d = (double)t;
+        d /= 1e9;
     }
+    return d;
 }
 
 PyObject *

Original file line number	Diff line number	Diff line change
`@@ -332,16 +332,21 @@ _PyTime_FromMillisecondsObject(_PyTime_t t, PyObject obj, _PyTime_round_t roun`
`332`	`332`	`double`
`333`	`333`	`_PyTime_AsSecondsDouble(_PyTime_t t)`
`334`	`334`	`{`
	`335`	`+ /* volatile avoids optimization changing how numbers are rounded */`
	`336`	`+ volatile double d;`
	`337`	`+`
`335`	`338`	`if (t % SEC_TO_NS == 0) {`
`336`	`339`	`_PyTime_t secs;`
`337`	`340`	`/* Divide using integers to avoid rounding issues on the integer part.`
`338`	`341`	`1e-9 cannot be stored exactly in IEEE 64-bit. */`
`339`	`342`	`secs = t / SEC_TO_NS;`
`340`		`- return (double)secs;`
	`343`	`+ d = (double)secs;`
`341`	`344`	`}`
`342`	`345`	`else {`
`343`		`- return (double)t / 1e9;`
	`346`	`+ d = (double)t;`
	`347`	`+ d /= 1e9;`
`344`	`348`	`}`
	`349`	`+ return d;`
`345`	`350`	`}`
`346`	`351`
`347`	`352`	`PyObject *`