Comparing two ways of initializing an int pointer

Question

Suppose I have a pointer

int *x;

Then I need to let the pointer point to an int of value, say 42.

Should I do this:

   *x = 42;

or this:

  int y = 42;
  x = &y;

? What is the usual practice?

Answer 1

After this declaration

int *x;

the pointer x either is equal to NULL (if it is declared outside any function) or has an indeterminate value. So dereferencing the pointer like

*x = 42;

invokes undefined behavior.

You can write either

int y = 42;
x = &y;

or

x = malloc( sizeof( int ) );
*x = 42;