C - Difference between "char var[]" and "char *var" ?

Question

I am expecting that both following vectors have the same representation in RAM:

char a_var[] = "XXX\x00";
char *p_var  = "XXX";

But strange, a call to a library function of type f(char argument[]) crushs the running application if I call it using f(p_var). But using f(a_var) is Ok!

Why?

Answer 1

At a guess, the function f modifies the contents of the string passed to it.

Answer 2

The first creates an array of char containing the string. The contents of the array can be modified. The second creates a character pointer which points to a string literal. String literals cannot be modified.

Answer 3

Nice question.

It's answered on section 6 of the C-FAQ.

Answer 4

Arrays can be treated (generally) as pointers but that doesn't mean that they are always interchangeable. As the other said, your p_var points to a literal, something static that cannot be changed. It can point to something else (e.g. p_var = &a_var[0]) but you can't change the original value that you specified by quotes....

A similar problem is when you are define a variable as an array in one file, and then extern-use it as a pointer.

Regards