Literal string initializer for a character array

Question

In the following rules for the case when array decays to pointer:

An lvalue [see question 2.5] of type array-of-T which appears in an expression decays (with three exceptions) into a pointer to its first element; the type of the resultant pointer is pointer-to-T.

(The exceptions are when the array is the operand of a sizeof or & operator, or is a literal string initializer for a character array.)

How to understand the case when the array is "literal string initializer for a character array"? Some example please.

Thanks!

Answer 1

The three exceptions where an array does not decay into a pointer are the following:

Exception 1. — When the array is the operand of sizeof.

int main() {    int a[10];    printf("%zu", sizeof(a)); /* prints 10 * sizeof(int) */     int* p = a;    printf("%zu", sizeof(p)); /* prints sizeof(int*) */ } 

Exception 2. — When the array is the operand of the & operator.

int main() {     int a[10];     printf("%p", (void*)(&a)); /* prints the array's address */      int* p = a;     printf("%p", (void*)(&p)); /*prints the pointer's address */ } 

Exception 3. — When the array is initialized with a literal string.

int main() {     char a[] = "Hello world"; /* the literal string is copied into a local array which is destroyed after that array goes out of scope */      char* p = "Hello world"; /* the literal string is copied in the read-only section of memory (any attempt to modify it is an undefined behavior) */ }