c - sizeof for a null terminated const char*

Question

const char* a;

how do I make sure that string 'a' is null terminated? when a = "abcd" and I do sizeof(a), I get 4. Does that mean its not null-terminated? if it were, I would have gotten 5 ?

Answer 1

sizeof(a) gives you the size of the pointer, not of the array of characters the pointer points to. It's the same as if you had said sizeof(char*).

You need to use strlen() to compute the length of a null-terminated string (note that the length returned does not include the null terminator, so strlen("abcd") is 4, not 5). Or, you can initialize an array with the string literal:

char a[] = "abcd";
size_t sizeof_a = sizeof(a); // sizeof_a is 5, because 'a' is an array not a pointer

The string literal "abcd" is null terminated; all string literals are null terminated.