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Re: Refactoring a #define definition
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Re: Refactoring a #define definition


  • Subject: Re: Refactoring a #define definition
  • From: Quincey Morris <email@hidden>
  • Date: Sat, 25 Jul 2015 18:03:44 +0000

On Jul 25, 2015, at 10:37 , Carl Hoefs <email@hidden> 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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