Question

This came up as one of the code review comments.

Is it a good idea to check for NULL before calling delete for any object?

I do understand delete operator checks for NULL internally and is redundant but the argument put forth was delete as an operator can be overloaded and if the overloaded version doesn’t check for the NULL it may crash. So is it safe and reasonable to assume that if and when delete will be overloaded it will check for the NULL or not?
In my understanding its reasonable to assume the first case that overloaded delete shall take care of the NULL check, and the review point doesn’t hold good. What do you think?

Answer 1

No, don’t check for null. The standard says that delete (T*)0; is valid. It will just complicate your code for no benefits. If operator delete is overloaded it’s better to check for null in the implementation of the operator. Just saves code lines and bugs.

EDIT: This answer was accepted and upvoted, yet, in my opinion, it was not very informative. There is one missing piece in all answers here, and, for conscience sake, let me add this last piece here.

The standard actually says in [basic.stc.dynamic], at least since C++03:

Any allocation and/or deallocation functions defined in a C++ program, including the default versions in the library, shall conform to the semantics specified in 3.7.4.1 and 3.7.4.2.

Where the referenced sections, as well as some other places in the standard listed in other answers, say that the semantics of passing a null pointer are a no-op.