Initializing a dynamically allocated array with a specific value in C

Question

So, I have dynamically allocated memory for an array and I want initialize all its values to a specific value (which is an element of an enumeration).

Here's what I've done so far:

    typedef enum{APPLE, BANANA, ORANGE} fruit;
    typedef struct Smoothie Smoothie;
    struct Smoothie {
        fruit* tab;
    };

This is all the structures I've defined so far. Now, to create the "Smoothie", I do the following:

    Smoothie init(size_t n) {
         Smoothie* juice = malloc(sizeof(Smoothie));
         if (juice == NULL) {
             //error msg in case the allocation has failed.
         }
         juice->tab = calloc(n, sizeof(fruit));
         if (juice->tab == NULL) {
              //error msg in case the allocation has failed.
         }
         memset(juice->tab, APPLE, n*sizeof(fruit));
         return *juice;
    }

My question is the following. From what I've been able to read on the internet, I know that calloc() already initializes all the values of the array at 0. In an enumeration, all the elements have a numerical value (by default, my enumeration has the following values: Apple = 0 BANANA = 1 ORANGE = 2). So, since I want to initialize all the values of my array to APPLE, is it very useful to use memset() ?

In other words, what happens if I do not use memset()? How can I be sure that the compiler will understand that the values in my array are fruit variables and not just integers?

PS: I know that I could use a loop ot initilize my array, but the whole point of this is to actually avoid using the loop.

Answer 1

So, since I want to initialize all the values of my array to APPLE, is it very useful to use memset()?

No. memset() fills an area with a byte value. The size of an enum can vary, but it is normally an int, which is larger than a byte. You will fill your memory with something undefined. (Except of course for the enum member with the value 0)

How can I be sure that the compiler will understand that the values in my array are fruit variables and not just integers?

You already did that by declaring it of type fruit. But it doesn't help much, because the conversion between integer and enum value in C is implicit.

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All in all, if you need to initialize memory to an enum value other than 0, you will need to write a loop. If you indeed want the value corresponding to 0, calloc() will do, it doesn't matter as 0 is still 0 :)