On Fri, Oct 26, 2012 at 1:35 AM, Shawn Steele <[email protected]> wrote: > I sort of have a fundamental problem with the solution. Eg: If it were > actually unused, it'd be GC'd. Since it isn't GC'd, something must be > holding a reference to it. So if you force it to be gone, or clear all the > properties, or whatever, seems to me that then you'd just start throwing > random errors in the code that tried to use the "freed" object? That might > be even harder to track down.
On the contrary, "TypeError: Cannot read property 'prop' of undefined", with a stack trace, is WAY easier to track down than "The RSS on my server gradually rises, until the operating system kills it, which happens about every 4 hours." Fast failure is not as good as success, but it's better than anything else. > On Thu, Oct 25, 2012 at 4:16 PM, Isaac Schlueter <[email protected]> wrote: >> It'd be really nice if JS had a way to explicitly delete an object. > > I guess you mean ... a way to set all the refs to a object to undefined. Yes, exactly. On Fri, Oct 26, 2012 at 1:20 AM, John J Barton <[email protected]> wrote: >> var obj = {} >> var foo = { ref: obj } > > I assume that in your real life, you don't know 'foo' but somehow you > know that foo.ref is never used? Well, you know that IF foo.ref is used, it's an error, and ought to throw. Also, it's quite easy to check if the property exists, and set it to a new object if so. It's common to have things like: if (!this._parser) { this._parser = new ParserThingie(); } In this example, imagine that parsers are expensive to create. So, we try to reuse them (danger!), and over time, our program grows until we have some code paths where the parsers are not getting all of their data removed properly. If the parser has a ref to an object that has a reference to some other thing, etc., then you've got a memory leak. This exact situation happened in Node's HTTP library a few months ago, and was very tedious to fix. We quite easily identified one of the things in the chain, and that it must have been linked in some way to an HTTP parser (or else it would have been GC'ed). It would have been much easier to just find the point where we know that the HTTP response object should be "finished", and forcibly remove any references to it. > Since you know "obj" can you set it to be a getter that returns undefined? Yeah, but the purpose of this is to take *away* the ref that you already *have*. What good is a getter that returns undefined, once you've already gotten it? Closing the barn door after the horse has left. > Deleting all of the properties of obj would solve the problem as well I > assume. But that is a bit more whack-a-mole, and expensive. Ultimately, what we did was move all of the addon properties on parsers to a single object, and delete that object when we re-use the http parser. _______________________________________________ es-discuss mailing list [email protected] https://mail.mozilla.org/listinfo/es-discuss
