为什么 (1 && !A) 在 C++ 预处理器中

Question

In some c++ file I found

#ifndef
#define A (1 && !B)
#endif

(with B having a default vale that can be overridden at compile time). What is the difference with

#ifndef
#define A (!B)
#endif

Is it in order to prevent warnings on some specific compiler?
(Exact code is in the Unreal Engine, I only simplified the macro names.)

Answer 1

Nobody is perfect, not even the authors of the Unreal Engine.

Setting aside any possibility of operator overloading, the type and values of the two expressions are identical. I suspect (and it's only a hunch), that the author is forgetting that the type of (!B) is a bool in C++.

(1 && !B) is more explicitly perhaps a bool type as it contains the && operator.