[v2.0.11] Invalid Memory Read/Write with JsRT.ahk on FreeLibrary call Topic is solved

[RaptorX]

I am wondering if anybody else is experiencing this issue reported by one of the people I work with:

Seems like after the JsRT.ahk library created by @lexikos exits and tries to free the loaded dll, Autohotkey tries to read an invalid location in memory and we end up getting an error on program exit

Code: Select all

; plugin.js file
function filter_data(selected_text)
{
	return [ { text : 'hey man'} ];
}

Code: Select all

; test.ahk file
#SingleInstance

#Include <JsRT>

js_plugin := (JsRT.Edge)()
plugin_code := FileRead(A_ScriptDir "\plugin.js")
try js_plugin.Exec(plugin_code)
catch Error as e
	msgbox e.What " " e.Message

com_matches := js_plugin.filter_data("test test")

matches := []
loop com_matches.length
{
	match := com_matches.%A_Index-1%
	matches.Push({text : "hi"})
}

MsgBox matches.length

Everything works great until after pressing the OK button on the message box and we end up with this error:

Error IMG

image.png (159.5 KiB) Viewed 801 times

Any ideas whether this is an Autohotkey bug or am I doing something wrong here?

[thqby]

com_matches := 0
Perhaps it is necessary to release objects from JSRT before exiting

[thqby]

These objects follow the default release order when the script exits.

Code: Select all

com_matches := unset
js_plugin := unset
matches := unset

[V2User]

JsRT.ahk library created by @lexikos

May you give a link of this library for me? I would appreciate it.

[wineguy]

@V2User https://github.com/Lexikos/ActiveScript.ahk/tree/master

[RaptorX]

These objects follow the default release order when the script exits.

Code: Select all

com_matches := unset
js_plugin := unset
matches := unset

sadly this doesnt help with the issue:

image.png (55.83 KiB) Viewed 603 times

[thqby]

The above code simulates the order in which the objects are released when the script exits, you must release them in the correct order to avoid this error.

Code: Select all

com_matches := matches := unset
js_plugin := unset

[V2User]

@V2User https://github.com/Lexikos/ActiveScript.ahk/tree/master

Thank you very much!

[RaptorX]

The above code simulates the order in which the objects are released when the script exits, you must release them in the correct order to avoid this error.

Code: Select all

com_matches := matches := unset
js_plugin := unset

Sadly this makes no difference.

[thqby]

This is a typo. matches is not an object from JsRT, match is.

[lexikos]

It is by design that the main JsRT object's destructor calls FreeLibrary. The program can't know whether there are any objects implemented by the library still referenced by the script, and the library itself probably doesn't keep track of how many of its objects are "alive". Even if it did, I'm not sure that the library could or should prevent itself from being unloaded.

I recall seeing similar problems with ActiveX in old scripts, where it was necessary to destroy the GUI before the script exits (or maybe it was because the script explicitly unloaded the library on exit). Otherwise, the process would crash on exit, because the GUI was destroyed after the ActiveX library was unloaded.

It might have been better to omit the FreeLibrary call and instead load the library exactly once, locking it in for the lifetime of the process. However, since (iirc) it isn't possible to have JScript within a WebBrowser control and JsRT working in the same process, allowing JsRT to be unloaded might provide some flexibility.