Macro definition stored by preprocessor

Question

Shouldn't I be getting warning or error message after declaring macro in this way:

#define c 123
#define a b
#define b c

The code worked flawlessly - so just like variable definition, is macro definition stored somewhere?

Sergey Kalinichenko · Accepted Answer · 2020-12-21 20:32:11Z

1

This is perfectly fine, because preprocessor does not act upon macro definitions until the point of expansion. That is why the order does not matter: as long as each macro has a definition to which it could be expanded when your code makes a reference to it, the preprocessor is happy. This applies to macros that rely on other macros for their expansion.

One consequence of this behavior is that the relative order of macro declarations does not change the end result.

answered Dec 21, 2020 at 20:32

Sergey Kalinichenko

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