On Nov 10, 11:26 am, "David Parks" <[EMAIL PROTECTED]> wrote:
> Hi, I've been playing with the very simple script shown below. I've set up
> an embedded debugger application so I can watch the script execution line by
> line.
>
> What I have been trying to answer is exactly how garbage collection works in
> Rhino.
>
> In this example I have defined a variable "x" on line 1, then, on line 2 I
> decide I no longer need the variable, so I set it to null.
>
> At each line of the script, the debugger pauses and I am performing the
> following steps:
> 1) run System.gc()
> 2) this.wait(5000)
> 3) printing out a list of all variables stored in the top-level
> scope
>
> At some point I was hoping that x would be de-allocated (removed from the
> scope), however it never happens, it always remains visible in the top level
> scope.
>
> What is necessary for a variable to be garbage collected? I will be
> executing a large number of concurrent scripts, and memory is of concern to
> me.
>
> Thanks!
> David
>
> ______________________________________________________
>
> var x=1;
> x=null;
> var y=2;
> z=3;
> function goHere(a){
> var b=5;
> c=6;
> return (a+b+c);}
>
> var d = goHere(10);
> y = null;
> var f = c;
> var g=true;
>
> ______________________________________________________
>
> Results (with only outputting the value of "x"):
>
> At Line #: 1 : [var x = 1;]
> x: [EMAIL PROTECTED]
> At Line #: 2 : [x = null;]
> x: 1.0
> At Line #: 3 : [var y = 2;]
> x: null
> At Line #: 4 : [z = 3;]
> x: null
> At Line #: 10 : [var d = goHere(10);]
> x: null
> At Line #: 5 : [function goHere(a) {]
> At Line #: 6 : [ var b = 5;]
> At Line #: 7 : [ c = 6;]
> At Line #: 8 : [ return (a + b + c);]
> At Line #: 11 : [ y = null;]
> x: null
> At Line #: 12 : [var f = c;]
> x: null
> At Line #: 13 : [var g = true;]
> x: null
>
> Process finished with exit code 0
> ______________________________________________________
If you want to remove variable "x" from the scope, try "delete x".
Otherwise Rhino must keep "x" defined--people would be surprised if
setting a variable to null resulted in the variable itself
disappearing!
More generally, you'll presumably want to have a different scope for
each script execution. When you're done with each script you can then
release the reference to the scope and the entire scope should be
available for collection.
Thanks,
Norris
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