Hi Guys
I wanted to demonstrate a bad memory bug that seems to apply to all the CC apps that I tried.
The leak is relevant to all the persistent engines. It probably has been around from the beginning of ExtendScript.
If one has a function and that function has a nested function in the form of var foo = function then all the nested functions within the wrapper function will be stuck in memory and every time one call the outer function the inner functions will be created (which is not necessarily great) and stored in memory. Garbage collection will not help.
Here's a simple example
No leak
function outer() {
function inner1(){}
function inner2(){}
function inner3(){}
}
// At this point we should have 4 functions in memory
outer();
outer();
outer();
outer();
// At this point we should still only have 4 functions in memory
// At this point we have 4 functions in memory
Leak
function outer() {
var inner1 = function(){};
function inner2(){}
function inner3(){}
}
// At this point we should have 4 functions in memory
outer();
outer();
outer();
outer();
// At this point we should still only have 4 functions in memory
// AT THIS POINT WE HAVE 16 FUNCTIONS IN MEMORY
Note it's not just the "var" function that leaks, the "var" function causes all the functions to leak.
The are 2 possible work-arounds that I can think of.
1) Don't use "var" functions, this is not generally recommended and linters will show errors if you do that freely but it might still be an option here.
2) Use Prototypes the instead of inner functions, this has the pro of not having the inner functions created on each calling or the outer function and the con of a lack of privacy.
I was wondering if others had any comments on this.
Also Marc Autret​ one posted a fancy dancy memory listing script using an undocumented $ method and a flashy UI I thought that might be useful for investigating but I can't find it. So if anyone can share a link for that it would be appreciated.
The below snippet demonstrates the leak, The $.leak function is probably similar to the summary difference function by Dirk Becker​ his site was offline and I decided to write my own version.
Don't forget to escape the #targetengine line if not executing in InDesign.
// DEMO
#targetengine transient // Comment this line out is not on InDesign
$.leak = $.leak || function(){
var oldSummary, newSummary, summaryObject, diffObject, key, diffArrray, report, count, value;
oldSummary = this.oldSummary || {};
newSummary = $.summary();
summaryObject = {};
diffObject = {};
newSummary.replace(/(\d+) (\S+)/g, function(whole, count, prop){
var diff;
count = +count;
summaryObject[prop] = count;
diff = count - (oldSummary[prop] || 0);
if (diff) {
diffObject[prop] = diff;
}
});
for (key in oldSummary){
if(!summaryObject[key]){
diffObject[key] = -oldSummary[key];
}
}
this.oldSummary = summaryObject;
diffArrray = [];
for (key in diffObject){
value = diffObject[key];
if (value > 0) { value = '+' + value;}
diffArrray.push([key, '\t' + value , '\t' + summaryObject[key]]);
}
diffArrray.sort(function(a,b){
if (a[1] === b[1]) { return 0;}
if (+a[1] > +b[1]) { return -1;}
return 1;
});
count = diffArrray.length;
if(!count) {return 'No change from last $.leak()';}
report = diffArrray.join('\n').replace(/,/g, ': ');
return count + ' memory change' + (count > 1 ? 's' : '') + '\n' + diffArrray.join('\n').replace(/,/g, ': ');
};
$.leak();
$.leak();
function withVarFunction(){
// As soon as we have a var foo = function all inner functions leak!
var innerFunction1 = function(){};
function innerFunction2(){};
function innerFunction3(){};
}
withVarFunction();
withVarFunction = null;
$.gc();
$.gc();
alert('withVarFunction\n' +$.leak());
function withoutVarFunction(){
function innerFunction1 (){};
function innerFunction2(){};
function innerFunction3(){};
}
withoutVarFunction();
$.gc();
$.gc();
alert('withoutVarFunction\n' +$.leak());
withoutVarFunction = null;
$.gc();
$.gc();
alert('After null\n' +$.leak());
Regards
Trevor
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