Is it possible to specify the size of an array using `strlen`?

Question

Is it possible to use strlen while declaring a new string?

Example:

char a[]="Hello world";
char b[strlen(a)]; // alloc memory to string b equal to the string length of a

If not, then what is the solution if I don't want to directly enter the length of another string?

And I'm unable to use the strrev function. I get the following error

error-implicit declaration of function 'strrev' is invalid in C99

How to fix this?

Answer 1

Yes, it is possible. But you should add an extra space for the null character if you want b to be exactly the same that a.

char a[] = "Hello world";
char b[strlen(a) + 1];

I think strrev() is not included in any standard c library.