Re: Concerning the necessity of include guards

From	David Brown <david.brown@hesbynett.no>
Newsgroups	comp.lang.c
Subject	Re: Concerning the necessity of include guards
Date	2020-02-24 22:37 +0100
Organization	A noiseless patient Spider
Message-ID	<r31fnc$t6b$1@dont-email.me> (permalink)
References	<20200224220814.34562e1774fd4d2c65f171a0@gmail.com> <87k14b4vv1.fsf@bsb.me.uk>

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On 24/02/2020 20:40, Ben Bacarisse wrote:
> Anton Shepelev <anton.txt@gmail.com> writes:
> 
>> A reviewer has recently declared it a fault in my library
>> that its .h file does not use an include guard, whereas I
>> deliberately decided not to use one, because the library
>> exports only functions, but no types.  Its header file is
>> therefore designed for inclusion into .c files, but not into
>> other .h files.
> 
> What "export" means is not 100% clear in C.  You mean, I think, is that
> the .h file declares, and possibly defines, only functions.  If it only
> declares functions (probably the usual meaning of "export"), then I
> can't see how it can matter if someone includes it in another .h file.
> 
>> What is your opinion?  Is it good practice to wrap each and
>> every header file in an include guard?
> 
> If there are no definitions at all, I think I wouldn't bother.  But I'd
> understand if someone wants it done as a matter of habit.
> 

It should not make any difference to any code using this header.  But as 
you say, many people would feel it looks more like a complete and 
ready-to-user header file if the guards are included.  Certainly it will 
be useful if other features (types, macros, etc.) are added at a later date.

Include guards also make the compilation more efficient (many compilers 
have very fast skipping of duplicate headers with include guards).  I 
can't imagine the effect will be measurable if you just have a few 
function declarations, but it can be a reason people have for such habits.

To the OP - why did you choose not to have a guard?

Thread

Concerning the necessity of include guards Anton Shepelev <anton.txt@gmail.com> - 2020-02-24 22:08 +0300
  Re: Concerning the necessity of include guards Bonita Montero <Bonita.Montero@gmail.com> - 2020-02-24 20:28 +0100
  Re: Concerning the necessity of include guards Ben Bacarisse <ben.usenet@bsb.me.uk> - 2020-02-24 19:40 +0000
    Re: Concerning the necessity of include guards David Brown <david.brown@hesbynett.no> - 2020-02-24 22:37 +0100
      Re: Concerning the necessity of include guards Anton Shepelev <anton.txt@g{oogle}mail.com> - 2020-02-25 14:13 +0300
        Re: Concerning the necessity of include guards David Brown <david.brown@hesbynett.no> - 2020-02-25 13:03 +0100
          Re: Concerning the necessity of include guards Anton Shepelev <anton.txt@gmail.com> - 2020-02-29 01:14 +0300
            Re: Concerning the necessity of include guards Bart <bc@freeuk.com> - 2020-02-28 22:36 +0000
              Re: Concerning the necessity of include guards Anton Shepelev <anton.txt@gmail.com> - 2020-02-29 13:28 +0300
            Re: Concerning the necessity of include guards Jorgen Grahn <grahn+nntp@snipabacken.se> - 2020-02-29 00:08 +0000
            Re: Concerning the necessity of include guards Richard Damon <Richard@Damon-Family.org> - 2020-02-29 07:05 -0500
            Re: Concerning the necessity of include guards David Brown <david.brown@hesbynett.no> - 2020-03-01 15:01 +0100
  Re: Concerning the necessity of include guards Lew Pitcher <lew.pitcher@digitalfreehold.ca> - 2020-02-24 14:52 -0500
    Re: Concerning the necessity of include guards Bonita Montero <Bonita.Montero@gmail.com> - 2020-02-24 21:19 +0100
      Re: Concerning the necessity of include guards Lew Pitcher <lew.pitcher@digitalfreehold.ca> - 2020-02-24 15:48 -0500
        Re: Concerning the necessity of include guards Bonita Montero <Bonita.Montero@gmail.com> - 2020-02-24 21:53 +0100
          Re: Concerning the necessity of include guards Lew Pitcher <lew.pitcher@digitalfreehold.ca> - 2020-02-24 17:26 -0500
            Re: Concerning the necessity of include guards David Brown <david.brown@hesbynett.no> - 2020-02-25 00:08 +0100
              Re: Concerning the necessity of include guards Thiago Adams <thiago.adams@gmail.com> - 2020-02-24 15:24 -0800
                Re: Concerning the necessity of include guards Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2020-02-24 22:20 -0800
                Re: Concerning the necessity of include guards David Brown <david.brown@hesbynett.no> - 2020-02-25 09:52 +0100
            Re: Concerning the necessity of include guards Bonita Montero <Bonita.Montero@gmail.com> - 2020-02-25 08:12 +0100
              Re: Concerning the necessity of include guards David Brown <david.brown@hesbynett.no> - 2020-02-25 09:55 +0100
                Re: Concerning the necessity of include guards Bonita Montero <Bonita.Montero@gmail.com> - 2020-02-25 10:35 +0100
                Re: Concerning the necessity of include guards David Brown <david.brown@hesbynett.no> - 2020-02-25 13:13 +0100
                Re: Concerning the necessity of include guards Bonita Montero <Bonita.Montero@gmail.com> - 2020-02-25 13:50 +0100
                Re: Concerning the necessity of include guards David Brown <david.brown@hesbynett.no> - 2020-02-25 18:33 +0100
                Re: Concerning the necessity of include guards Bonita Montero <Bonita.Montero@gmail.com> - 2020-02-25 18:38 +0100
                Re: Concerning the necessity of include guards David Brown <david.brown@hesbynett.no> - 2020-02-25 18:42 +0100
                Re: Concerning the necessity of include guards Bonita Montero <Bonita.Montero@gmail.com> - 2020-02-25 18:46 +0100
                Re: Concerning the necessity of include guards Bart <bc@freeuk.com> - 2020-02-25 19:35 +0000
                Re: Concerning the necessity of include guards David Brown <david.brown@hesbynett.no> - 2020-02-25 21:18 +0100
                Re: Concerning the necessity of include guards Bonita Montero <Bonita.Montero@gmail.com> - 2020-02-26 06:40 +0100
                Re: Concerning the necessity of include guards James Kuyper <jameskuyper@alumni.caltech.edu> - 2020-02-25 12:12 -0800
                Re: Concerning the necessity of include guards James Kuyper <jameskuyper@alumni.caltech.edu> - 2020-02-25 11:55 -0800
                Re: Concerning the necessity of include guards David Brown <david.brown@hesbynett.no> - 2020-02-25 21:37 +0100
                Re: Concerning the necessity of include guards scott@slp53.sl.home (Scott Lurndal) - 2020-02-26 02:39 +0000
                Re: Concerning the necessity of include guards Real Troll <real.troll@trolls.com> - 2020-02-25 23:10 -0400
                Re: Concerning the necessity of include guards chad <cdalten@gmail.com> - 2020-02-27 05:39 -0800
  Re: Concerning the necessity of include guards Jorgen Grahn <grahn+nntp@snipabacken.se> - 2020-02-24 22:23 +0000
  Re: Concerning the necessity of include guards Tim Rentsch <tr.17687@z991.linuxsc.com> - 2020-02-24 21:17 -0800
    Re: Concerning the necessity of include guards Guillaume <message@bottle.org> - 2020-02-25 13:03 +0100

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