Status: Untriaged
Owner: ----
CC: [email protected]
Labels: Type-Bug Priority-Medium HW-IA32 OS-Windows
New issue 4369 by [email protected]: Wrong execution result (around
computation involving Math.floor(-0), maybe?)
https://code.google.com/p/v8/issues/detail?id=4369
Version: V8 4.5.103.14 (Chrome 45.0.2454.26 beta-m 32-bits)
OS: Windows7 x64
Version: V8 4.6.62 (Chrome 46.0.2478.0 canary 32-bits)
OS: Windows7 x64
It did not reproduce on 64-bits Chrome on MacOSX and Linux.
I haven't checked 64-bits Windows Chrome yet.
What steps will reproduce the problem?
1. Open the attached HTML file in Chrome.
2. Open JavaScript console. (Ctrl-Shift-J)
3. Reload (F5) several times.
What is the expected output?
The console should show "(3000x) true".
What do you see instead?
Something like "(187x) true" "false" "(2812x) true".
The reproduction code (quoted below) is a smallest reduction I could get
from my real JS app.
It should always be the case that q.y == -(1-1) == -0 but it sometimes
(once per hundreds of runs) keeps being 1.
function f(p) {
var yy = -(p.y - 1);
var xx = Math.floor(yy) - 2; // This line should be no-op, but needed to
reproduce the issue.
p.y = yy;
}
function test() {
var y = 1;
var q = {y: y};
f(q);
console.log(q.y != 1);
}
for(var n=0; n!=3000; ++n)
test();
I tried several variations of the code above, and as far as I tested all
the cases I got such wrong values involved computing Math.floor(-0). So it
may be something around there, but it's just my wild guess.
+yangguo, according to this issue tracker log you look familiar around
Math.floor stuff. Could you help triaging the issue?
Attachments:
floor.html 325 bytes
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