Runtime formation and execution at runtime

This is a discussion on Runtime formation and execution at runtime within the C Programming forums, part of the General Programming Boards category; Thanks matsp. Very good idea. I have made some syntax changes to your program and it works very good. Really ...

  1. #16
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    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);
    */
    }

  2. #17
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    I suppose I should have pointed out that I just typed it in, with no compilation/checking - it was meant to show the concept, not really be a complete solution...

    And calling realloc every time is probably not a very clever way to make sure you have enough memory for the variables... Keep a "high water mark", and only call realloc if you go over that limit.

    --
    Mats
    Compilers can produce warnings - make the compiler programmers happy: Use them!
    Please don't PM me for help - and no, I don't do help over instant messengers.

  3. #18
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    Location
    PA, USA
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    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.

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