Question

void sizeof_test2();

void sizeof_test2()
{
    int array[5];
    size_t arr_size = sizeof(array);

    printf( "sizeof:\n"
            "array = %d\n"
            "arr_size = %d\n", sizeof(array), sizeof(arr_size));
}

GCC compiler output:

sizeof_test2.c: In function `sizeof_test2':  
sizeof_test2.c:6: error: `size_t' undeclared (first use in this function)  
sizeof_test2.c:6: error: (Each undeclared identifier is<br>
reported only once sizeof_test2.c:6: error: for each function it<br>
appears in.) sizeof_test2.c:6: error: parse error before "arr_size"<br>
sizeof_test2.c:10: error: `arr_size' undeclared (first use in this<br>
function) make[2]:  [build/Debug/Cygwin-Windows/sizeof_test2.o]<br>
Error 1 make[1]:  [.build-conf] Error 2<br>  

Don’t know why I’m getting this error, what’s the correct way of displaying a size_t type through printf?

Answer 1

size_t type is defined in stddef.h header (and other headers, for example stdio.h).

Note that in your program your are using printf function so you already have to include stdio.h.