sizeof for a character array

Question

why do I get results 6, and then 8 by from the following code? I searched through the posts but cannot find an exact match of my question. Thanks.

#include <stdio.h>

void getSize(const char *str)
{
        printf("%d\n", sizeof(str)/sizeof(char));
}

int main()
{
        char str[]="hello";
        printf("%d\n", sizeof(str)/sizeof(char));
        getSize(str);
}

Answer 1

In your getSize() function, str is a pointer. Therefore sizeof(str) returns the size of a pointer. (which is 8 bytes in this case)

In your main() function, str is an array. Therefore sizeof(str) returns the size of the array.

This is one of the subtle differences between arrays and pointers.