Thread: Runtime formation and execution at runtime

Thanks matsp. Very good idea.

I have made some syntax changes to your program and it works very good. Really a good idea.

Code:

#include <stdio.h>
#include <stdlib.h>

#define ADD_VAR(t, x) add_var(#t, #x, &x)
#define REMOVE_VAR(x) remove_var(#x)

int total = 0;
typedef struct {
    char *type_list;
    char *name_list;
    void *addr_list;
    } store_list;

store_list *store = NULL;

void add_var(const char *type, const char *name, void *addr)
{
   total++;
   store = realloc(store, total * sizeof(store_list));
   /* Store type, name and addr in some sort of stack/list/array/etc.  */
   store[total-1].type_list = type;
   store[total-1].name_list = name;
   store[total-1].addr_list = (int *) addr;
}

void remove_var(const char *name)
{
    /* // remove the last added variable of that name.  */
}

const char *get_fmt(const char *type)
{
    const static struct {
                char *type;
                char *fmt;
                } table[] =
                            {
                                { "int", "%d" },
                                { "char *", "%s" },
                                { NULL, NULL }
                            };
                int i;

                for(i = 0; table[i].type; i++)
                {
                    if(strcmp(type, table[i].type) == 0)
                        return table[i].fmt;
                }
                return NULL;
}

void print_var(const char *name)
{
    int i = 0;
    store_list *found;

    found = NULL;

    /* Find name in list.  */
    for (i=0; i<total; i++)
    {
        if (strcmp(store[i].name_list, name) == 0)
        {
            found = &store[i];
        }
    }

    if (found)
    {
        const char *fmt = get_fmt(found->type_list);
        char buffer[100];
        if (!fmt)
            printf("Unknown format %s\n", found->type_list);
        else
        {
            sprintf(buffer, "%s = %s\n", name, fmt);
            if (strcmp(fmt, "%d") == 0)
            {
                printf(buffer, *(int *)found->addr_list);
            }
            else if (strcmp(fmt, "%s") == 0)
            {
                printf(buffer, (char *)found->addr_list);
            }
        }
    }
    else
    {
        printf("Could not find variable\n");
    }
}

int main()
{
    int x = 8;
    int y = 7;
    char str[20] = "foo";
    char name[20];;

    ADD_VAR(char *, str);
    ADD_VAR(int, x);
    ADD_VAR(int, y);

    scanf("%s", name);
    print_var(name);

/*
    REMOVE_VAR(str);
    REMOVE_VAR(y);
    REMOVE_VAR(x);
*/
}

You are right. I know you had just pointed out the general structire of the program. I just completed it for the benefit of others too. (without remove).

I have used realloc so that only needed space is allocated (as against array). I could have used linked list, but I wanted some quick testing.

This is just a prototype program.

Thanks for a very good idea.