Is this allowed under the standard?
Is it required to compile?
Does it have the semantics I would expect?

   #if 0   // was ...
     // old code
   #else   // changing to ...
     // new code
   #endif  // ... end change

thanks,

-jeff


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Jeffrey Juliano (juliano@cs.unc.edu) wrote:

>    #if 0   // was ...
>      // old code
>    #else   // changing to ...
>      // new code
>    #endif  // ... end change

> Is this allowed under the standard?

Yes.

> Is it required to compile?

Yes.

> Does it have the semantics I would expect?

If you expect that the comments after your #if/#else/#endif are ignored,
then yes.

The standard says that legal comments are replaced by a non-newline
whitespace, and end of line comments are legal at the end of *any* line.
As long as you don't do line continuation with a backslash, like:

#if 0  // was ... \
func();

you are OK.  The line continuation above results in the function call
becoming part of the #if 0, and thus, part of the *comment* after the
#if 0, which would probably not be what you intended.

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