An optimal debugger would show the textual location in the source code where live references to a particular object were created. Optimally, it would be possible to get the references during debug mode via the "tooltip" that comes up when hovering over a variable.
Isaac could then solve his problem trivially by adding a debugger where he would have called free and look at what other places in the source are still holding references. On Fri, Oct 26, 2012 at 12:34 PM, John J Barton <[email protected] > wrote: > On Fri, Oct 26, 2012 at 11:58 AM, Isaac Schlueter <[email protected]> wrote: > > So, yes, you can certainly use debugging tools to find which objects > > are leaking. But, there are times when you have a program where > > something is leaking, and you read through the code, and see that > > there is no possible way that it could be leaking (but it is, as > > reality sometimes stubbornly refuses to be told what to do.) > > > > Use-after-free bugs are not great, but they are relatively easy to > > track down. And, in general, a program that crashes when it does > > something wrong, is handling it exactly right. Slowly leaking memory > > is much harder to diagnose, and usually much harder to correct. > ... > > > > Yehuda's "action at a distance" complaint is definitely a valid > > concern. However, note that an object can't be freed unless you have > > a reference to the object. Thus, any code that would set my reference > > to undefined could only do so if it was also capable of mutating the > > object in any other way (adding/removing properties, etc.) > > > > So, we already have this: > > > > function () { > > // acquire a ref from some external code > > // no way of knowing what else is sharing this object > > var x = func() > > x.foo = 'bar' > > // other code... > > doAnotherThing() > > // not guaranteed! > > assert(x.foo === 'bar') > > FWIW, Querypoint debugging will be able to tell you "where was x.foo > changed?". > > > } > > > > Whenever you have a reference to an object that is shared with some > > other code, there's the potential for action at a distance. > > Seems like other questions we'd like to answer include "where was the > object refed by 'x' defined?" "Where are other references to that > object taken?" "Where was any property of 'x' written?" These seem > feasible. > > jjb > _______________________________________________ > es-discuss mailing list > [email protected] > https://mail.mozilla.org/listinfo/es-discuss > -- Yehuda Katz (ph) 718.877.1325
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