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Asked: 2026-06-10T14:54:34+00:00

Another question about the C standard. I have tested this and I always get

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Another question about the C standard. I have tested this and I always get NULL < ptr true, where ptr is any pointer different from NULL. But I know that the Standard says that pointer arithmetic and comparison is only defined inside the bounds of an array. I’m just not sure if the particular comparison NULL < ptr is legal.

Edit: I have been reading K&R and I found the following quote:

Any pointer can be meaningfully compared for equality or inequality with zero. But the behavior is undefined for arithmetic or comparisons with pointers that do not point to members of the same array.

I’m not sure if this affects the answers already given to this question. In any case, I am still unsure whether p > NULL is always guaranteed or not to return true, where p is a pointer !=NULL.

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  1. Editorial Team

    NULL < ptr is invalid: a null pointer cannot be relationally compared. To do so yields undefined behavior.

    You are correct that you can only relationally compare pointers that point into the same object (either to elements in an array or subobjects of an aggregate). Since a null pointer does not point at any object, you can’t relationally compare it with anything.

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