Pointer initialization in C

Question

In C why is it legal to do

char * str = "Hello"; 

but illegal to do

int * arr = {0,1,2,3}; 

Answer 1

I guess that's just how initializers work in C. However, you can do:

int *v = (int[]){1, 2, 3}; /* C99. */ 

Answer 2

As for C89:

"A string", when used outside char array initialization, is a string literal; the standard says that when you use a string literal it's as if you created a global char array initialized to that value and wrote its name instead of the literal (there's also the additional restriction that any attempt to modify a string literal results in undefined behavior). In your code you are initializing a char * with a string literal, which decays to a char pointer and everything works fine.

However, if you use a string literal to initialize a char array, several magic rules get in action, so it is no longer "as if an array ... etc" (which would not work in array initialization), but it's just a nice way to tell the compiler how the array should be initialized.

The {1, 2, 3} way to initialize arrays keeps just this semantic: it's only for initialization of array, it's not an "array literal".