How to resolve the "storage size of variable isn't known" error

Take a look at the code in C below that defines struct xyx ​and initializes an object of that struct:

#include <stdio.h>
struct xyx {
    int x;
    int y;
};
int main(void)
{
    struct xyz a;
    a.x = 100;
    printf("%d\n", a.x);
    return 0;
}

Executing the code above gives the error main.c:13:16: storage size of ‘a’ isn’t known.

Have a look at the code again!

In our main, we have created the object a of struct type xyz; however, our struct declaration above had the name xyx.

The compiler is unable to identify the amount of space that needs to be allocated to x because there is no pre-defined or user-defined struct xyz; hence, it gives the error that the storage size of a is not known.

The solution is pretty simple, xyz just needs to be changed to xyx. Take a look at the working code below:

#include <stdio.h>
struct xyx {
    int x;
    int y;
    char c;
    char str[20];
    int arr[2];
};
int main(void)
{
    struct xyx a;
    a.x = 100;
    printf("%d\n", a.x);
    return 0;
}

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