GDNative C example Issue

totoro

I'm following this tutorial: https://docs.godotengine.org/en/stable/tutorials/plugins/gdnative/gdnative-c-example.html#doc-gdnative-c-example

All appeared to go well until the last few steps...

I have the following code:

extends Control

onready var data = preload("res://bin/simple.gdns").new()
#var data

# Called when the node enters the scene tree for the first time.
#func _ready():
#	data = preload("res://bin/simple.gdns").new()

func _on_Button_pressed():
	$Label.text = "Data = " + data.get_data()

... and I get the following error

Parse Error: Unexpected "Identifier" in class body.

It appears to target "onready"....?

If I move it into the _ready() function, then it's the new() which causes the issue due to being null

Is this me for using Godot 4 or can you suggest where else I may have gone wrong (it's late for me, but I've checked through the tut a few times now)

Many thanks

cybereality

Can you try load instead of preload? I recall that worked for someone with a similar issue.

totoro

Hi, thankyou, but sadly noooo... It's still saying error(5,1) which indicates to me that it may be the onready

Later I'll move onto the C++ variation as that's where I'm heading anyway, but I may also try this again from scratch.

Thankyou

Megalomaniak

Did you make sure that your Class Name matches the class name you defined in your c source?

@totoro said: ... and I get the following error

Parse Error: Unexpected "Identifier" in class body.

This definitely reads like the issue is in your C source.

@totoro said: It appears to target "onready"....?

That is likely because that is the closest the GDScript debugger can trace to the source of the problem(which is likely in your other file).

totoro

I believe I checked for the naming issue last night, as in Simple is capitalised within the C code.

I was watching GamesFromScratch tonight and he showed the following page: https://github.com/godotengine/gdnative-demos/tree/master/c/simple So I used the code from there, then compiled using the docs method using gcc and then the git method using clang.

Having shifted the gd script about, the error is now about failing to call new() on a null object. (Maybe a compiling issue?)

Sooooo... Unsure, so going to move onto the C++ example instead for now and revisit if need be

Thankyou both :)

BTW FYI I'm on Fedora 32

Megalomaniak

c code example should have instances of the word simple only in either all lower or all upercase, but not both mixed. Ie. function names are all lowercase like:


godot_variant simple_get_data(...

And the native API registers are all caps:


nativescript_api->godot_nativescript_register_method(p_handle, "SIMPLE", "get_data", attributes, get_data);

even the file name is simple.c and not Simple.c

totoro

In the git version that is the case, the docs version uses Simple:

void GDN_EXPORT godot_nativescript_init(void *p_handle) {
    godot_instance_create_func create = { NULL, NULL, NULL };
    create.create_func = &simple_constructor;

    godot_instance_destroy_func destroy = { NULL, NULL, NULL };
    destroy.destroy_func = &simple_destructor;

    nativescript_api->godot_nativescript_register_class(p_handle, "Simple", "Reference",
            create, destroy);

    godot_instance_method get_data = { NULL, NULL, NULL };
    get_data.method = &simple_get_data;

    godot_method_attributes attributes = { GODOT_METHOD_RPC_MODE_DISABLED };

    nativescript_api->godot_nativescript_register_method(p_handle, "Simple", "get_data",
            attributes, get_data);
}

https://docs.godotengine.org/en/stable/tutorials/plugins/gdnative/gdnative-c-example.html#doc-gdnative-c-example

I did however amend to SIMPLE when adapted to the git version, to no avail...

Cheers

totoro

Yeah not sure with all that, however I've followed a cpp module tutorial and it fits my needs perfectly. Other than a couple of directory changes (core/object) it was as easy as everything else in Godot... Really, great work guys n gals, thanks

Megalomaniak

Its entirely possible the gdnative tutorial is perhaps a bit out of date in some fashion.

amit42

I am also getting similar error, I followed the documentations, following are my codes

//simple.c
#include <gdnative_api_struct.gen.h>
#include <string.h>

const godot_gdnative_core_api_struct *api = NULL;
const godot_gdnative_ext_nativescript_api_struct *nativescript_api = NULL;

void *simple_constructor(godot_object *p_instance, void *p_method_data);
void simple_destructor(godot_object *p_instance, void *p_method_data, void *p_user_data);

godot_variant simple_get_data(godot_object *p_instance, void *p_method_data,
        void *p_user_data, int p_num_args, godot_variant **p_args);

void GDN_EXPORT godot_gdnative_init(godot_gdnative_init_options *p_options) {
    api = p_options->api_struct;

    // Now find our extensions.
    for (unsigned int i = 0; i < api->num_extensions; i++) {
        switch (api->extensions[i]->type) {
            case GDNATIVE_EXT_NATIVESCRIPT: {
                nativescript_api = (godot_gdnative_ext_nativescript_api_struct *)api->extensions[i];
            }; break;
            default: break;
        }
    }
}

void GDN_EXPORT godot_gdnative_terminate(godot_gdnative_terminate_options *p_options) {
    api = NULL;
    nativescript_api = NULL;
}

void GDN_EXPORT godot_nativescript_init(void *p_handle) {
    godot_instance_create_func create = { NULL, NULL, NULL };
    create.create_func = &simple_constructor;

    godot_instance_destroy_func destroy = { NULL, NULL, NULL };
    destroy.destroy_func = &simple_destructor;

    nativescript_api->godot_nativescript_register_class(p_handle, "simple", "Node2D",
            create, destroy);

    godot_instance_method get_data = { NULL, NULL, NULL };
    get_data.method = &simple_get_data;

    godot_method_attributes attributes = { GODOT_METHOD_RPC_MODE_DISABLED };

    nativescript_api->godot_nativescript_register_method(p_handle, "simple", "get_data",
            attributes, get_data);
}
typedef struct user_data_struct {
    char data[256];
} user_data_struct;

void *simple_constructor(godot_object *p_instance, void *p_method_data) {
    user_data_struct *user_data = api->godot_alloc(sizeof(user_data_struct));
    strcpy(user_data->data, "World from GDNative!");

    return user_data;
}
void simple_destructor(godot_object *p_instance, void *p_method_data, void *p_user_data) {
    api->godot_free(p_user_data);
}
godot_variant simple_get_data(godot_object *p_instance, void *p_method_data,
        void *p_user_data, int p_num_args, godot_variant **p_args) {
    godot_string data;
    godot_variant ret;
    user_data_struct *user_data = (user_data_struct *)p_user_data;

    api->godot_string_new(&data);
    api->godot_string_parse_utf8(&data, user_data->data);
    api->godot_variant_new_string(&ret, &data);
    api->godot_string_destroy(&data);

    return ret;
}


//gdscript
extends Node2D
func _ready():
	var data = load("res://main.gdns").new()
	data.get_data()
	pass 
func _process(delta):
	$player.position.x += 5*delta

getting following errors

E 0:00:00.522   get_dynamic_library_symbol_handle: Can't resolve symbol godot_gdnative_init, error: 127.
  <C++ Error>   Method failed. Returning: ERR_CANT_RESOLVE
  <C++ Source>  platform/windows/os_windows.cpp:2415 @ get_dynamic_library_symbol_handle()
  <Stack Trace> main.gd:7 @ _ready()

E 0:00:00.529   initialize: Failed to obtain godot_gdnative_init symbol
  <C++ Source>  modules/gdnative/gdnative.cpp:360 @ initialize()
  <Stack Trace> main.gd:7 @ _ready()

E 0:00:00.537   get_symbol: No valid library handle, can't get symbol from GDNative object
  <C++ Source>  modules/gdnative/gdnative.cpp:501 @ get_symbol()
  <Stack Trace> main.gd:7 @ _ready()

E 0:00:00.544   init_library: No nativescript_init in "res://native c/bin/lib-windows.dll" found
  <C++ Source>  modules/gdnative/nativescript/nativescript.cpp:1506 @ init_library()
  <Stack Trace> main.gd:7 @ _ready()

peniwize

I have encountered this exact same problem (line 9 fails with error about null object). I tried renaming Simple to simple in simple.c and it still didn't work. I also tried adding script class name simple to simple.gdns and that didn't help. I also noticed that attempting to use onready to initialize a variable to the label in the scene does not work (see attached image):

onready var _label = get_node("Label")

Has support for the onready keyword been dropped in 4.x?

DaveTheCoder

Has support for the onready keyword been dropped in 4.x? I haven't seen the official documentation, but I read in a post that it's been changed to something like this in 4.x:

@onready
var ...

peniwize

Thank you DaveTheCoder! That does resolve the Unexpected "Identifier" in class body error. Unfortunately I'm still getting the Attempt to call function 'new' in base 'NativeScript' on a null instance. error on line 9. I'll post if/when I figure it out.

DaveTheCoder

I see that the onready change for 4.x is documented here: https://docs.godotengine.org/en/latest/tutorials/scripting/gdscript/gdscript_basics.html#onready-annotation

Maybe that version of the documentation could be helpful for the other error.