Wrong null callback parameter treating about bindings-generator

[Teivaz]

bool js_gaf_GAFAsset_create(JSContext *cx, uint32_t argc, jsval *vp)
{
    jsval *argv = JS_ARGV(cx, vp);
    bool ok = true;
    if (argc == 2) {
        std::string arg0;
        std::function<void (std::basic_string<char> *)> arg1;
        ok &= jsval_to_std_string(cx, argv[0], &arg0);
        do {
            std::shared_ptr<JSFunctionWrapper> func(new JSFunctionWrapper(cx, JS_THIS_OBJECT(cx, vp), argv[1]));
            auto lambda = [=](std::basic_string<char>* larg0) -> void {
                jsval largv[1];
                do {
                    if (larg0) {
                        js_proxy_t *jsProxy = js_get_or_create_proxy<std::basic_string<char>>(cx, (std::basic_string<char>*)larg0);
                        largv[0] = OBJECT_TO_JSVAL(jsProxy->obj);
                    } else {
                        largv[0] = JSVAL_NULL;
                    }
                } while (0);
                jsval rval;
                bool ok = func->invoke(1, &largv[0], rval);
                if (!ok && JS_IsExceptionPending(cx)) {
                    JS_ReportPendingException(cx);
                }
            };
            arg1 = lambda;
        } while(0)
        ;
        JSB_PRECONDITION2(ok, cx, false, "js_gaf_GAFAsset_create : Error processing arguments");
        gaf::GAFAsset* ret = gaf::GAFAsset::create(arg0, arg1);
        jsval jsret = JSVAL_NULL;
        do {
        if (ret) {
            js_proxy_t *jsProxy = js_get_or_create_proxy<gaf::GAFAsset>(cx, (gaf::GAFAsset*)ret);
            jsret = OBJECT_TO_JSVAL(jsProxy->obj);
        } else {
            jsret = JSVAL_NULL;
        }
    } while (0);
        JS_SET_RVAL(cx, vp, jsret);
        return true;
    }
    JS_ReportError(cx, "js_gaf_GAFAsset_create : wrong number of arguments");
    return false;
}

where

typedef std::function<void(std::string*)> Delegate_t;
GAFAsset* GAFAsset::create(const std::string& gafFilePath, Delegate_t delegate)
{
    std::string path;
    ...
    if(delegate)
    {
        delegate(&path)
    }
    ...
}

After calling delegate the following line in generated binding will produce crash:

largv[0] = OBJECT_TO_JSVAL(jsProxy->obj);

as jsProxy is a null pointer;

[Teivaz]

How about enclosing lambda in

do {
    if (!JSVAL_IS_NULL(argv[1]))
    {
        std::shared_ptr<JSFunctionWrapper> func(new JSFunctionWrapper(cx, JS_THIS_OBJECT(cx, vp), argv[1]));
        auto lambda = [=](std::basic_string<char>* larg0) -> void {
                ...
        };
        arg1 = lambda;
    }
    else
    {
        arg1 = nullptr;
    }
} while(0);

[pandamicro]

Hi, @Teivaz Thanks for your suggestions and your pull request, I agree with the general idea and I have commented on your PR, please take a look.