Force evaluation order in set_date_fields (#268)

Author: chqrlie

quickjs.c

@@ -46793,7 +46793,7 @@ static __exception int get_date_fields(JSContext *ctx, JSValue obj,
             return FALSE; /* NaN */
         d = 0;        /* initialize all fields to 0 */
     } else {
-        d = dval;
+        d = dval;     /* assuming -8.64e15 <= dval <= -8.64e15 */
         if (is_local) {
             tz = -getTimezoneOffset(d);
             d += tz * 60000;
@@ -46839,33 +46839,63 @@ static double time_clip(double t) {
         return NAN;
 }
 
-/* The spec mandates the use of 'double' and it fixes the order
+/* The spec mandates the use of 'double' and it specifies the order
    of the operations */
 static double set_date_fields(double fields[], int is_local) {
-    int64_t y;
-    double days, d, h, m1;
-    int i, m, md;
-
-    m1 = fields[1];
-    m = fmod(m1, 12);
-    if (m < 0)
-        m += 12;
-    y = (int64_t)(fields[0] + floor(m1 / 12));
-    days = days_from_year(y);
-
-    for(i = 0; i < m; i++) {
-        md = month_days[i];
+    double y, m, dt, ym, mn, day, h, s, milli, time, tv;
+    int yi, mi, i;
+    int64_t days;
+    volatile double temp;  /* enforce evaluation order */
+
+    /* emulate 21.4.1.15 MakeDay ( year, month, date ) */
+    y = fields[0];
+    m = fields[1];
+    dt = fields[2];
+    ym = y + floor(m / 12);
+    mn = fmod(m, 12);
+    if (mn < 0)
+        mn += 12;
+    if (ym < -271821 || ym > 275760)
+        return NAN;
+
+    yi = ym;
+    mi = mn;
+    days = days_from_year(yi);
+    for(i = 0; i < mi; i++) {
+        days += month_days[i];
         if (i == 1)
-            md += days_in_year(y) - 365;
-        days += md;
+            days += days_in_year(yi) - 365;
+    }
+    day = days + dt - 1;
+
+    /* emulate 21.4.1.14 MakeTime ( hour, min, sec, ms ) */
+    h = fields[3];
+    m = fields[4];
+    s = fields[5];
+    milli = fields[6];
+    /* Use a volatile intermediary variable to ensure order of evaluation
+     * as specified in ECMA. This fixes a test262 error on
+     * test262/test/built-ins/Date/UTC/fp-evaluation-order.js.
+     * Without the volatile qualifier, the compile can generate code
+     * that performs the computation in a different order or with instructions
+     * that produce a different result such as FMA (float multiply and add).
+     */
+    time = h * 3600000;
+    time += (temp = m * 60000);
+    time += (temp = s * 1000);
+    time += milli;
+
+    /* emulate 21.4.1.16 MakeDate ( day, time ) */
+    tv = (temp = day * 86400000) + time;   /* prevent generation of FMA */
+    if (!isfinite(tv))
+        return NAN;
+
+    /* adjust for local time and clip */
+    if (is_local) {
+        int64_t ti = tv < INT64_MIN ? INT64_MIN : tv >= 0x1p63 ? INT64_MAX : (int64_t)tv;
+        tv += getTimezoneOffset(ti) * 60000;
     }
-    days += fields[2] - 1;
-    h = fields[3] * 3600000 + fields[4] * 60000 +
-        fields[5] * 1000 + fields[6];
-    d = days * 86400000 + h;
-    if (is_local)
-        d += getTimezoneOffset(d) * 60000;
-    return time_clip(d);
+    return time_clip(tv);
 }
 
 static JSValue get_date_field(JSContext *ctx, JSValue this_val,
@@ -47475,6 +47505,7 @@ static JSValue js_date_getTimezoneOffset(JSContext *ctx, JSValue this_val,
     if (isnan(v))
         return JS_NAN;
     else
+        /* assuming -8.64e15 <= v <= -8.64e15 */
         return JS_NewInt64(ctx, getTimezoneOffset((int64_t)trunc(v)));
 }
 

tests/test_builtin.js

@@ -84,14 +84,22 @@ function assert(actual, expected, message) {
     if (arguments.length == 1)
         expected = true;
 
-    if (actual === expected)
-        return;
-
-    if (actual !== null && expected !== null
-    &&  typeof actual == 'object' && typeof expected == 'object'
-    &&  actual.toString() === expected.toString())
-        return;
-
+    if (typeof actual === typeof expected) {
+        if (actual === expected) {
+            if (actual !== 0 || (1 / actual) === (1 / expected))
+                return;
+        }
+        if (typeof actual === 'number') {
+            if (isNaN(actual) && isNaN(expected))
+                return true;
+        }
+        if (typeof actual === 'object') {
+            if (actual !== null && expected !== null
+            &&  actual.constructor === expected.constructor
+            &&  actual.toString() === expected.toString())
+                return;
+        }
+    }
     throw Error("assertion failed: got |" + actual + "|" +
                 ", expected |" + expected + "|" +
                 (message ? " (" + message + ")" : ""));
@@ -594,20 +602,54 @@ function test_date()
     assert(d.toISOString(), "2017-09-22T18:10:11.091Z");
     a = Date.parse(d.toISOString());
     assert((new Date(a)).toISOString(), d.toISOString());
+    s = new Date("2020-01-01T01:01:01.123Z").toISOString();
+    assert(s,    "2020-01-01T01:01:01.123Z");
+    // implementation defined behavior
     s = new Date("2020-01-01T01:01:01.1Z").toISOString();
-    assert(s ==  "2020-01-01T01:01:01.100Z");
+    assert(s,    "2020-01-01T01:01:01.100Z");
     s = new Date("2020-01-01T01:01:01.12Z").toISOString();
-    assert(s ==  "2020-01-01T01:01:01.120Z");
-    s = new Date("2020-01-01T01:01:01.123Z").toISOString();
-    assert(s ==  "2020-01-01T01:01:01.123Z");
+    assert(s,    "2020-01-01T01:01:01.120Z");
     s = new Date("2020-01-01T01:01:01.1234Z").toISOString();
-    assert(s ==  "2020-01-01T01:01:01.123Z");
+    assert(s,    "2020-01-01T01:01:01.123Z");
     s = new Date("2020-01-01T01:01:01.12345Z").toISOString();
-    assert(s ==  "2020-01-01T01:01:01.123Z");
+    assert(s,    "2020-01-01T01:01:01.123Z");
     s = new Date("2020-01-01T01:01:01.1235Z").toISOString();
-    assert(s ==  "2020-01-01T01:01:01.124Z");
+    assert(s ==  "2020-01-01T01:01:01.124Z" ||      // QuickJS
+           s ==  "2020-01-01T01:01:01.123Z");       // nodeJS
     s = new Date("2020-01-01T01:01:01.9999Z").toISOString();
-    assert(s ==  "2020-01-01T01:01:02.000Z");
+    assert(s ==  "2020-01-01T01:01:02.000Z" ||      // QuickJS
+           s ==  "2020-01-01T01:01:01.999Z");       // nodeJS
+
+    assert(Date.UTC(2017), 1483228800000);
+    assert(Date.UTC(2017, 9), 1506816000000);
+    assert(Date.UTC(2017, 9, 22), 1508630400000);
+    assert(Date.UTC(2017, 9, 22, 18), 1508695200000);
+    assert(Date.UTC(2017, 9, 22, 18, 10), 1508695800000);
+    assert(Date.UTC(2017, 9, 22, 18, 10, 11), 1508695811000);
+    assert(Date.UTC(2017, 9, 22, 18, 10, 11, 91), 1508695811091);
+
+    assert(Date.UTC(NaN), NaN);
+    assert(Date.UTC(2017, NaN), NaN);
+    assert(Date.UTC(2017, 9, NaN), NaN);
+    assert(Date.UTC(2017, 9, 22, NaN), NaN);
+    assert(Date.UTC(2017, 9, 22, 18, NaN), NaN);
+    assert(Date.UTC(2017, 9, 22, 18, 10, NaN), NaN);
+    assert(Date.UTC(2017, 9, 22, 18, 10, 11, NaN), NaN);
+    assert(Date.UTC(2017, 9, 22, 18, 10, 11, 91, NaN), 1508695811091);
+
+    // TODO: Fix rounding errors on Windows/Cygwin.
+    if (!['win32', 'cygwin'].includes(os.platform)) {
+        // from test262/test/built-ins/Date/UTC/fp-evaluation-order.js
+        assert(Date.UTC(1970, 0, 1, 80063993375, 29, 1, -288230376151711740), 29312,
+               'order of operations / precision in MakeTime');
+        assert(Date.UTC(1970, 0, 213503982336, 0, 0, 0, -18446744073709552000), 34447360,
+               'precision in MakeDate');
+    }
+    //assert(Date.UTC(2017 - 1e9, 9 + 12e9), 1506816000000);  // node fails this
+    assert(Date.UTC(2017, 9, 22 - 1e10, 18 + 24e10), 1508695200000);
+    assert(Date.UTC(2017, 9, 22, 18 - 1e10, 10 + 60e10), 1508695800000);
+    assert(Date.UTC(2017, 9, 22, 18, 10 - 1e10, 11 + 60e10), 1508695811000);
+    assert(Date.UTC(2017, 9, 22, 18, 10, 11 - 1e12, 91 + 1000e12), 1508695811091);
 }
 
 function test_regexp()