sizeof() showing different output

Question

Here is a snippet of C99 code:

int main(void)
{
    char c[] = "\0";
    printf("%d %d\n", sizeof(c), strlen(c));

    return 0;
}

The program is outputting 2 0. I do not understand why sizeof(c) implies 2 seeing as I defined c to be a string literal that is immediately NULL terminated. Can someone explain why this is the case? Can you also provide a (some) resource(s) where I can investigate this phenomenon further on my own time.

Answer 1

didn't understand why size of is showing 2.

A string literal has an implicit terminating null character, so the ch[] is actually \0\0, so the size is two. From section 6.4.5 String literals of the C99 standard (draft n1124), clause 5:

In translation phase 7, a byte or code of value zero is appended to each multibyte character sequence that results from a string literal or literals

As for strlen(), it stops counting when it encounters the first null terminating character. The value returned is unrelated to the sizeof the array that is containing the string. In the case of ch[], zero will be returned as the first character in the array is a null terminator.

Answer 2

In C, "" means: give me a string and null terminate it for me.

For example arr[] = "A" is completely equivalent to arr[] = {'A', '\0'};

Thus "\0" means: give me a string containing a null termination, then null terminate it for me.

arr [] = "\0"" is equivalent to arr[] = {'\0', '\0'};