What's the meaning of #define without replacement in C/C++? [duplicate]

Question

This question already has answers here:

Are empty macro definitions allowed in C? How do they behave? (3 answers)

Closed 9 years ago.

I encountered some codes as the following:

#define MY_IDENTIFIER
void someCode() 
{
    ...
    MY_IDENTIFIER
    ...
}

What's the upper code doing ?

Answer 1

Absolutely nothing. The pre-processor is simply replacing MY_IDENTIFIER with nothing wherever it encounters it.