Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!tut.cis.ohio-state.edu!ucbvax!decwrl!labrea!glacier!jbn
From: jbn@glacier.STANFORD.EDU (John B. Nagle)
Newsgroups: comp.software-eng
Subject: Re: Recursive #includes
Keywords: recursive includes, modularity
Message-ID: <18136@glacier.STANFORD.EDU>
Date: 27 Feb 89 18:52:18 GMT
References: <570@marob.MASA.COM> <2630@pegasus.ATT.COM>
Reply-To: jbn@glacier.UUCP (John B. Nagle)
Organization: Stanford University
Lines: 24

In article <2630@pegasus.ATT.COM> psrc@pegasus.ATT.COM (Paul S. R. Chisholm) writes:
>In article <570@marob.MASA.COM>, samperi@marob.MASA.COM (Dominick Samperi) writes:
>> <contents of foo.h>:
>> 
>> #ifndef H_FOO
>> #define H_FOO
>>...stuff...
>> #endif

      It does add to your compile times, since the entire file you're not
including has to be read and parsed.  

      I support the idea that #include should not include files "already
included".  The exact semantics of this need to be carefully defined,
so that it's well-defined whether #include <stdio.h> and "#include
"stdio.h" are considered to be identical, and the implications of pathnames
need to be thought out.  But it's a good idea.

      Given this, it would be normal for all .h files to contain includes
for any .h files they require, and creators of .c files could totally ignore
the internal dependency problems of the library.

      For those rare situations when you really want to insert a file
more than once, a new command, perhaps "#insert" should be defined.