在 C++ 中定义类时使用 #define 宏

Question

#define EXPORT_SPEC 

class EXPORT_SPEC CBoard {
.......
}

What is the use or purpose of EXPORT_SPEC in the above class definition.

how this class definition is different from normal class definition.

Ur help is highly appreciated.

Answer 1

None is the answer to your question. The macro has no value so it will be "removed" by the pre-processor. As el.pescado said, macros like this are used to build libraries (as opposed to stand-alone apps).

Answer 2

The point of the #define use is to specify a non-changing value. In the case you are mentioning, you would be able to set the name of a class according to some preference set in that #define call. Eg

#define CLASS_NAME "Employee"

class CLASS_NAME something {
...
}

In this case, you can change the class / object name by the #define call. I don't know if there is too much use in that, or at least not too much that I can think of.

This question was also addressed here .