Is NULL always false?

Question

Is it safe to assume that NULL always translates to false in C?

void *somePtr = NULL;

if (!somePtr) {
  /* This will always be executed? */
}
<         


        

Answer 1

According to me, it's not always safe to assume that. Since, depending on which headers have been included in a program, it can have been redefined. But according to the standard, the null pointer constant is guaranteed not to point to any real object and has a type void *.

In our case, the declaration void *somePtr = NULL could also be void *somePtr = 0 with 0 as null pointer.

“An integer constant expression with the value 0, or such an expression cast to type void *, is called a null pointer constant. If a null pointer constant is converted to a pointer type, the resulting pointer, called a null pointer, is guaranteed to compare unequal to a pointer to any object or function.” https://www.geeksforgeeks.org/few-bytes-on-null-pointer-in-c/

That simply means, evaluating *somePtr at that specific point could result to false.

Another reference can be https://www.gnu.org/software/libc/manual/pdf/libc.pdf at page 944 A.3 about NULL Pointer Constant