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Date: Sat, 12 Mar 2022 23:35:36 -0800
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Subject: Tracking PHP Objects In PHP C-API
From: sutabi@gmail.com (Joseph Montanez)

Hello,

What I am trying to do is hold onto another PHP object in an internal
struct.

 I.E:

<?php
$camera3d = new Camera3D();
$camera3d->position = new Vector3();
$camera3d->position->x++;

The reason for this is that the Camera3D struct has additional data I
need to track, so it cannot be an object of raw values.

// Vector3, 3 components
typedef struct Vector3 {
        float x; // Vector x component
        float y; // Vector y component
        float z; // Vector z component
} Vector3;

// Camera, defines position/orientation in 3d space
typedef struct Camera3D {
        Vector3 position; // Camera position
        Vector3 target; // Camera target it looks-at
        Vector3 up; // Camera up vector (rotation over its axis)
        float fovy; // Camera field-of-view apperture in Y (degrees)
in perspective, used as near plane width in orthographic
        int projection; // Camera projection: CAMERA_PERSPECTIVE or
CAMERA_ORTHOGRAPHIC
} Camera3D;

The idea is that when the $camera3d->position is modified, and when I
want to use the internal camera struct, I'll pull back the other PHP
object's internal values.

Right now it looks like this between Vector3 and Camera3D.

typedef struct _php_raylib_vector3_object {
        Vector3 vector3;
        HashTable *prop_handler;
        zend_object std;
} php_raylib_vector3_object;

typedef struct _php_raylib_camera3d_object {
        Camera3D camera3d;
        HashTable *prop_handler;
        php_raylib_vector3_object *position; // $camera3d->position
        php_raylib_vector3_object *target; // $camera3d->target
        php_raylib_vector3_object *up; // $camera3d->up
        zend_object std;
} php_raylib_camera3d_object;

I've looked at the PHP LibXML extension, its using its own reference
counting, while SQLITE only uses efree() when deconstructing. The
general issue I am running into is that other values are being
assigned, or worst memory being corrupted, this crashing.

Its terms of the getting for the camera3d position object, I make sure
to add a gc ref when providing the object.

// If someone calls $camera3d->position
static zend_object *
php_raylib_camera3d_get_position(php_raylib_camera3d_object *obj) /*
{{{ */
{
    GC_ADDREF(&obj->position->std);
    return &obj->position->std;
}
/* }}} */

Then for the setter I delref and addref.
// If someone calls $camera3d->position = new Vector3d(1,2,3);
static int php_raylib_camera3d_set_position(php_raylib_camera3d_object
*obj, zval *newval) /* {{{ */
{
    int ret = SUCCESS;
    if (Z_TYPE_P(newval) == IS_NULL) {
        // Cannot set this to null...
        return ret;
    }
    php_raylib_vector3_object *phpPosition = Z_VECTOR3_OBJ_P(newval);
    GC_ADDREF(&phpPosition->std);
    GC_DELREF(&obj->position->std);
    obj->position = phpPosition;
    obj->camera3d.position = phpPosition->vector3;
    return ret;
}
/* }}} */

All is okay until when I need to update the internal Camera3D struct
via an update function called before it used:
// This takes the PHP objects of positon, target and up and assigns
those values back to the raw camera struct.
void php_raylib_camera3d_update_intern(php_raylib_camera3d_object *intern) {
    intern->camera3d.position = intern->position->vector3; //
intern->position is php_raylib_vector3_object *
    intern->camera3d.target = intern->target->vector3; //
intern->position is php_raylib_vector3_object *
    intern->camera3d.up = intern->up->vector3; // intern->position is
php_raylib_vector3_object *
}

This works for the first time, but after creates an access error. Am I
missing something when tracking? When I need to provide a PHP object I
assumed I need to GC_ADDREF and the same was when replaced GC_DELREF.
But when it's initialized or accessed internally do I need to continue
to use those macros? I looked like LibXML as it has a similar concept
but it's manually tracked references. SQLite3 also does something
similar but only calls efree() when the root object is freed.

I have the code available for how it's constructed.
https://github.com/joseph-montanez/raylib-php/blob/develop/camera3d.c


Thanks,
Joseph Montanez


Thanks,
Joseph Montanez