access violation with call_with_this

[ctaggart]

I'm trying to use call_with_this like in #20, but I'm getting an access violation exception. If I choose to debug into it with Visual Studio, it shows this:

The code to reproduce is here:
https://github.com/ctaggart/typescript_ts/pull/2/files#diff-6382a243b48dc8580db0fb4e2fb6e26f
cargo run --example create

I'm using ChakraCore v1.7.0.

[ctaggart]

@darfink, ideas for how I can troubleshoot this? Is this my misunderstanding of lifetimes in Rust? I'll see about reproducing it in a short single script that I can paste here.

[ctaggart]

This works just fine, so my guess is that I'm doing something wrong with the guard and lifetimes.

extern crate chakracore;

use std::io::prelude::*;
use std::fs::File;

fn main() {
    let runtime = chakracore::Runtime::new().unwrap();
    let context = chakracore::Context::new(&runtime).unwrap();
    let guard = context.make_current().unwrap();

    // load typescript.js
    let js = "./node_modules/typescript/lib/typescript.js";
    let mut file = File::open(js).expect("unable to open the file");
    let mut contents = String::new();
    file.read_to_string(&mut contents).expect("unable to read the file");
    chakracore::script::eval(&guard, &contents).expect("invalid JavaScript code");

    // get ts variable
    let ts = guard.global().get(&guard, &chakracore::Property::new(&guard, "ts")).into_object().unwrap();

    // call createNode
    let function = ts.get(&guard, &chakracore::Property::new(&guard, "createNode")).into_function().unwrap();
    println!("got function createNode");
    let rv = function.call_with_this(&guard, &ts, &[
        &chakracore::value::Number::new(&guard, 3).into(),
        &chakracore::value::Number::new(&guard, -1).into(),
        &chakracore::value::Number::new(&guard, -1).into(),
    ]);
    println!("rv: {:?}", rv);
    let node = rv.unwrap().into_object().unwrap();

    // verify that the node kind is 3
    let kind = node.get(&guard, &chakracore::Property::new(&guard, "kind"));
    println!("kind: {:?}", kind);

}

[ctaggart]

If I introduce a struct that contains the guard, this blows up with the error. I'm not sure what I'm doing wrong with lifetimes yet.

extern crate chakracore;

use std::io::prelude::*;
use std::fs::File;

pub struct Js<'a> {
    guard: &'a chakracore::context::ContextGuard<'a>,
}

impl<'a> Js<'a> {
    pub fn new(guard: &'a chakracore::context::ContextGuard<'a>) -> Js<'a> {
        let js = "./node_modules/typescript/lib/typescript.js";
        let mut file = File::open(js).expect("unable to open the file");
        let mut contents = String::new();
        file.read_to_string(&mut contents).expect("unable to read the file");
        chakracore::script::eval(&guard, &contents).expect("invalid JavaScript code");
        Js { guard: guard }
    }
}

fn main() {
    let runtime = chakracore::Runtime::new().unwrap();
    let context = chakracore::Context::new(&runtime).unwrap();
    let guard = context.make_current().unwrap();

    let js = Js::new(&guard);
    let ts = js.guard.global().get(js.guard, &chakracore::Property::new(js.guard, "ts")).into_object().unwrap();
    
    // call createNode
    let function = ts.get(js.guard, &chakracore::Property::new(js.guard, "createNode")).into_function().unwrap();
    println!("got function createNode");
    let rv = function.call_with_this(js.guard, &ts, &[
        &chakracore::value::Number::new(js.guard, 3).into(),
        &chakracore::value::Number::new(js.guard, -1).into(),
        &chakracore::value::Number::new(js.guard, -1).into(),
    ]);
    println!("rv: {:?}", rv);
}

[ctaggart]

ping @darfink

[ctaggart]

If I pass in the ContextGuard to every function, I don't run into problems. It makes the API a bit more difficult to use, but I could probably live with it. I blogged about wrapping the TypeScript API here:

http://blog.ctaggart.com/2017/10/creating-and-printing-typescript-ast.html

[darfink]

I understand this is a belated solution, but I've identified the culprit.

The issue was never due to the lifetime introduced in conjunction with the ContextGuard, but that the contents of the source file was freed when the lexical scope exited, in this case freeing the contents variable.

Due to my previous experience with V8, I assumed ChakraCore behaved likewise regarding the parsing and execution of external JavaScript source code. Therefore I expected JsRun to parse the entire supplied source code, rendering it as a non-dependency.

I've created a fix for this by allocating a JsString instead, making ChakraCore responsible for managing the files' contents.

[darfink]

Fixed with ac890b4

[ctaggart]

Thanks @darfink! It works great.

[ctaggart]

I revised my prototype today and blogged about it. It works a lot better with this fixed.
http://blog.ctaggart.com/2018/03/creating-and-printing-typescript-ast.html