getting the type of element from array C

Question

I was wondering if it is possible in C to get the type from an element in an array. I have the following code, where you have to manually specify the type, but would like to remove the second argument.

#define ForEach( func, type, list)do {\
    int num_elements = sizeof(list) / sizeof(type);\
    int iter;\
    for( iter = 0; iter < num_elements; iter++)\
        func(list[iter]);\
    }while(0)

void display(int n) {
    printf("\n%d\n", n);
}

int main(void){
    int list [] = { 1,2,3,4,5,6,7,8,9,10};
    ForEach(display, int, list);
    return 0;
}

score 3 · Answer 1 · answered Apr 14 '17 at 16:24

For the purpose of this question - You can use sizeof operator on elements of the array as -

sizeof(list[0])

If you are using GCC (or anything GNU), there is an extenstion called typeof. You can do

sizeof(typeof(list[0]))

But the C way of doing it is directly use sizeof the element.

score 0 · Answer 2 · edited May 23 '17 at 12:32

0

I don't believe it is possible. What you can do is instead of

sizeof(type)

do

sizeof(list[0])

But this may not work for malloced arrays.

Read this post

edited May 23 '17 at 12:32

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answered Apr 14 '17 at 16:28

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Why exactly won't this work with `malloc`'d arrays? As long as you use the correct type for the pointer, it should work. – Ajay Brahmakshatriya Apr 14 '17 at 16:36
1

There is a huge difference between size of an array and size of an element. Here we are doing size of the element. It will work even on malloc'd arrays. – Ajay Brahmakshatriya Apr 15 '17 at 08:16

getting the type of element from array C

2 Answers2