In C, is the condition : "if(a != NULL)" the same as the condition "if(a)"? [duplicate]

Question

Let's say a is a pointer, and after allocating memory for it, I want to check if the memory was allocated successfully, I've seen two ways doing this :

if(a != NULL)

if(a)

What is the difference between the first and second statements ?

Answer 1

is the condition : if(a != NULL) the same as the condition if(a)?

They achieve the same purpose. The only real difference is in readability.

---

Their effect is the same, since they will result in the same thing.

NULL is a macro that is almost always 0, so:

if(a != NULL)

is equivalent to:

if(a != 0)

which is pretty similar to:

if(a)

since it will check if the expression a evaluates to true.

So, if a is a pointer, they will be the same. If it's not, then it will depend on how NULL is defined (which as I said is almost always 0).