Thread: dynamically allocate a structure

I am programming C on a VAX. I am trying to define a structure using an extern variable.

struct RF_MOVES rf_move_struct_p[rf_max_moves_ex]

The value, rf_max_moves_ex, is derived by reading a system logical early in a calling program. The value is then assigned to an extern variable. The structure is then defined in one of the calling program using the extern variable. When I compile this, I get the following message:

In the declaration of "rf_move_struct_p", "rf_max_moves_ex" is not constant, but occurs in a context that requires a constant expression.

I am pretty sure you can do this in VB, but that is not an option, looking for a way to accomplish this using C. Any suggestions would be greatly appreciated.

> struct RF_MOVES rf_move_struct_p[rf_max_moves_ex]

Is declared like this
struct RF_MOVES *rf_move_struct_p;


And space is actually allocated (when you know rf_max_moves_ex) as follows

rf_move_struct_p = malloc ( rf_max_moves_ex * sizeof(struct RF_MOVES) );

You can then access rf_move_struct_p[i] like any normal array.

Don't forget to
#include <stdlib.h>

And please remember to use a C compiler to compile it

Thanks for the timely reply

I tried your suggestion and I am now getting quite a few compiler errors in the statements where I reference the structure

rf_move_struct_p[i-y].move_status = MR$_NO_LOAD;
.................^
%CC-E-NEEDPOINTER, In this statement, "rf_move_struct_p" has a signed int type,
but occurs in a context that requires a pointer.
at line number 4364 in file
_______________________________
Here's a synopsis of what's happening:
_______________________________

In the calling program I defined the following (as suggested) above the main:
struct RF_MOVES *rf_move_struct_p;

later, I call the calling program with

sts$value = crp_build_link_list_part(&p_cat_id_no, rf_move_struct_p);

This compiles cleanly. In the called program, the prototype is

int crp_build_link_list_part (user_input_cat_id_no, rf_move_struct_p)

and I have the statement below the main

rf_move_struct_p = malloc(rf_max_moves_ex * sizeof(struct RF_MOVES));

When I compile the program I get the message listed at the top for all the times the structure is referenced. This is probably simple, but I'm not seeing it. I tried using the -> reference, but I got the same results.

Thanks for your help so far

> This compiles cleanly. In the called program, the prototype is
> int crp_build_link_list_part (user_input_cat_id_no, rf_move_struct_p)

Doesn't look much like a prototype to me

Should be something like

int crp_build_link_list_part ( int *user_input_cat_id_no, struct RF_MOVES * rf_move_struct_p) ;