#endif //

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3 total messages Started by Michael Cook Wed, 06 Mar 1996 20:51

#3607

Author: Michael Cook
Date: Wed, 06 Mar 1996 20:51

12 lines
1071 bytes

Is it legal to have //-style comments within a preprocessor directive?  If so,
that'd mean C++ compilers would be precluded from using ISO C preprocessors.

Michael.


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Re: #endif //

#3619

Author: Steve Clamage
Date: Wed, 06 Mar 1996 21:56

30 lines
2039 bytes

In article fsf@erawan.cognex.com, Michael Cook <mcook@cognex.com> writes:
>Is it legal to have //-style comments within a preprocessor directive?

Yes.

>  If so,
>that'd mean C++ compilers would be precluded from using ISO C preprocessors.

Preprocessing is not a separate translation step according to the C and
C++ language definitions. The preprocessing need not be an identifiable
step, nor is there any requirement to provide preprocessed output.

If an implementation chooses to make preprocessing a separate step (or
a separable step) it may do so. The preprocessing rules for C and C++ are 
not quite the same, due to //-comments in C++, so a shared preprocessor
would have to take that into account. Such shared preprocessors typically
take a command-line flag to say whether it is dealing with C or C++ code.

C will almost certainly adopt //-comments, and some C compilers currently
accept them anyway. Thus, the point will soon be moot.

---
Steve Clamage, stephen.clamage@eng.sun.com
---
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Re: #endif //

#3622

Author: Zefram
Date: Fri, 08 Mar 1996 17:07

19 lines
1698 bytes

Michael Cook  <mcook@cognex.com> wrote:
>Is it legal to have //-style comments within a preprocessor directive?  If so,
>that'd mean C++ compilers would be precluded from using ISO C preprocessors.

That is correct.  Comments are converted into spaces before
preprocessing occurs.  In practice, it is common for a single
preprocessor program to have two modes of operation, one in which //
starts a comment and one in which it does not.  That preprocessor can
then be used for both languages.  (Actually other options are needed
too, controlling which digraphs are recognised.)

-zefram
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