CODEWITHSUNDEEP
c++variablesconstantsc-preprocessoroverwrite
blubberbernd
blubberbernd

Reputation: 3701

Priority of #define vs. const declaration

can a #define "overwrite" a const variable or vice versa? Or will it lead to a compiler error?

//ONE
#define FOO 23
const int FOO = 42;

//TWO
const int FOO = 42;
#define FOO 23

What value will FOO have in both cases, 42 or 23?

Upvotes: 0

Views: 537

Answers (1)

Sarfaraz Nawaz
Sarfaraz Nawaz

Reputation: 361352

First one will give compilation error. Macros are visible from the point of their definition.

That is, first one is equivalent to:

//ONE
#define FOO 23
const int 23= 42; //which would cause compilation error

And second one is this:

//TWO
const int FOO = 42;
#define FOO 23 //if you use FOO AFTER this line, it will be replaced by 23

Since macros are dumb, in C++ const and enum are preferred over macros. See my answer here in which I explained why macros are bad, and const and enum are better choices.

Upvotes: 8

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