I agree, but for a blog post it is more concise (IS_CONST or anything that is long would take up a lot more screen real estate on my phone).

To determine if an expression is constant in C, one must determine if an expression in C is constant.

Would you expect IS_CONST to evaluate to the constant? With a name like that I would expect it to evaluate to true/false.

C here is asserting that the value inside is a constant and then evaluating to that constant.

Uh, you are right. C is the right name. It throws.

I mixed it up with a similar compile-time constness check in some of my libraries, where I decided if const of not. gcc throws, only clang could give me a proper answer.