OpenEuphoria

1. Attempting to subscript an atom Error[SOLVED]

• Posted by Icy_Viking Oct 14, 2022
• 1008 views
• Last edited Oct 17, 2022

Hello all,

When trying to wrap the add-on functions for Allegro, I came across this error: Attempting to subscript an atom

I posted the code from where the error is coming from. Let me know if more code is needed. I am using the FFI.e I'm not sure why I would get that error as it just returning a boolean variable.

Wrapper code

include std/ffi.e 
 
include allegro.e 
 
export constant prim = open_dll("allegro_primitives-5.2"), --this needed to have .dll added to the end 
 
				xal_get_allegro_primitives_version = define_c_func(prim,"al_get_allegro_primitives_version",{},C_UINT) --this was missing a "+" 
				 
public function al_get_allegro_primitives_version() 
	return c_func(xal_get_allegro_primitives_version,{}) 
end function 
 
 
export constant xal_init_primitives_addon = define_c_func(prim,"+al_init_primitives_addon",{},C_BOOL), 
				xal_is_primitives_addon_initialized = define_c_func(prim,"+al_is_primitives_addon_initialized",{},C_BOOL), 
				xal_shutdown_primitives_addon = define_c_proc(prim,"+al_shutdown_primitives_addon",{}), 
				xal_draw_prim = define_c_func(prim,"+al_draw_prim",{C_POINTER,C_POINTER,C_POINTER,C_INT,C_INT,C_INT},C_INT), 
				xal_draw_indexed_prim = define_c_func(prim,"+al_draw_indexed_prim",{C_POINTER,C_POINTER,C_POINTER,C_POINTER,C_INT,C_INT},C_INT), 
				xal_draw_vertex_buffer = define_c_func(prim,"+al_draw_vertex_buffer",{C_POINTER,C_POINTER,C_INT,C_INT,C_INT},C_INT), 
				xal_draw_indexed_buffer = define_c_func(prim,"+al_draw_indexed_buffer",{C_POINTER,C_POINTER,C_POINTER,C_INT,C_INT,C_INT},C_INT) 
				 
public function al_init_primitives_addon() 
	return c_func(xal_init_primitives_addon,{}) --error is coming from this line 
end function 
 
public function al_is_primitives_addon_initialized() 
	return c_func(xal_is_primitives_addon_initialized,{}) 
end function 
 
public procedure al_shutdown_primitives_addon() 
	c_proc(xal_shutdown_primitives_addon,{}) 
end procedure 

Demo program

--Simple Display Window demo 
--Draw primitive shapes 
 
include allegro.e 
include keycodes.e 
include std/ffi.e 
 
include primitives.e 
 
procedure main() 
 
 atom x = al_install_system(ALLEGRO_VERSION_INT,0) 
  
 atom a = al_init_primitives_addon() 
  
 if x = -1 then 
 	puts(1,"Failed to init Allegro!\n") 
 	abort(0) 
 end if 
  
 if a = -1 then 
 	puts(1,"Failed to init addon!\n") 
 	abort(0) 
 end if 
  
 atom dis = al_create_display(800,600) 
  
 if dis = -1 then 
 	puts(1,"Failed to create display!\n") 
 	abort(0) 
 end if 
  
 al_set_window_title(dis,"Primitive Demo") 
  
 sequence BLUE = al_map_rgb(0,0,255) 
 
 al_draw_line(10,10,10,10,BLUE,10)  
 
 al_flip_display() 
   
 al_rest(5.0) 
  
 al_destroy_display(dis) 
	 
end procedure 
 
main() 
 

3. Re: Attempting to subscript an atom Error

• Posted by Icy_Viking Oct 15, 2022
• 941 views

public function al_init_primitives_addon()  
object x 
 
          x = c_func(xal_init_primitives_addon,{}) --error is coming from this line  
 
return x 
end function  
 

export constant xal_init_primitives_addon = define_c_func(prim,"+al_init_primitives_addon",{},C_INT),  

 object a = al_init_primitives_addon()  

Thanks for trying to help Chris, but it didn't work. Same error came up.

5. Re: Attempting to subscript an atom Error

• Posted by Icy_Viking Oct 16, 2022
• 878 views

export constant xal_init_primitives_addon = define_c_func(prim,"+al_init_primitives_addon",{C_INT},C_BOOL),  
 
public function al_init_primitives_addon()  
	return c_func(xal_init_primitives_addon, 0) --error is coming from this line  
end function  
  
 

7. Re: Attempting to subscript an atom Error

• Posted by irv Oct 16, 2022
• 862 views

type xfn(atom x) -- type is your friend 
return x > -1 
end type 
 
export xfn  
  xal_init_primitives_addon = define_c_func(prim,"+al_init_primitives_addon",{},C_BOOL),              
  xal_is_primitives_addon_initialized = define_c_func(prim,"+al_is_primitives_addon_initialized",{},C_BOOL),  
  xal_shutdown_primitives_addon = define_c_proc(prim,"+al_shutdown_primitives_addon",{}),  
  xal_draw_prim = define_c_func(prim,"+al_draw_prim",{C_POINTER,C_POINTER,C_POINTER,C_INT,C_INT,C_INT},C_INT) 

9. Re: Attempting to subscript an atom Error[SOLVED]

• Posted by ghaberek (admin) Oct 17, 2022
• 819 views

Sorry I had a busy weekend so I wasn't able to reply in time. The problem here is simply that define_c_func() is returning -1 because it could not find the function name, and c_func() isn't checking the function ID correctly. I will get some more error-checking added soon to help with this.

FYI for anyone reading along, and I'll make sure the documentation reflects this as well, the indication of STDCALL (no plus) or CDECL (with plus) calling convention only affects 32-bit Windows and nothing else and I encourage everyone to use 64-bit Euphoria if they are on a 64-bit platform (which they should be) where the plus is silently ignored.

This is the core of the issue. I'm currently using negative function IDs in the wrappers for c_func/proc to avoid collision with the positive function IDs returned by the interpreter's own define_c_func/proc. I just need a few checks in there and then I'll call crash() if the ID is not valid, as the interpreter would do.

You can see the offending code and its lack of error checking here: https://github.com/ghaberek/libffi-euphoria/blob/main/include/std/ffi.e#L900

I'm entertaining the idea of adding some library name guessing features to open_dll(), which would help avoid needing a bunch of ifdef PLATFORM then blocks or having a bunch of failed attempts to load libraries that don't exist.

So for libraries that have a common root name, you'd just call open_dll("foobar") and it would try foobar.dll, libfoobar.so, etc. based on the current platform.

-Greg

11. Re: Attempting to subscript an atom Error[SOLVED]

• Posted by mitgedanken Oct 19, 2022
• 741 views

Sorry, but I must say something: You all are fantastic!