On Jul 25, 2015, at 10:37 , Carl Hoefs <[email protected]> wrote:
>
> Effectively, what the compiler does with a #define _is_ a global replace.

It’s not, though. Not in general.

1. It’s not global. A #define can be undefined and redefined.

2. It’s not unique. IIRC, the appearance of the define symbol inside its own 
definition is *not* subject to macro expansion.

3. Macro expansion happens as a separate lexical pass over the input. For 
example, if source lines are not compiled as a result of a define/if then it’s 
not clear what replacement might be suitable at refactoring. Or again, token 
pasting may simply produce incorrect results if macro names are arbitrarily 
changed around them.




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