From: Rob <rchristi AT robchris DOT demon DOT co DOT uk>
Newsgroups: comp.os.msdos.djgpp
Subject: Re: .h files unrecognised
Date: Tue, 17 Feb 1998 20:56:47 +0000
Organization: Spinner
Message-ID: <+AZ+QBAPmf60EwPb@robchris.demon.co.uk>
References: <34E59182 DOT 80F AT which DOT net> <34E5D9D3 DOT 5C94 AT cs DOT com>
 <+gId1FA6c350EwVR AT robchris DOT demon DOT co DOT uk> <34E8F811 DOT 3E1D AT cs DOT com>
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In article <34E8F811 DOT 3E1D AT cs DOT com>, John M. Aldrich <fighteer AT cs DOT com>
writes
>Rob wrote:
>> 
>> In article <34E5D9D3 DOT 5C94 AT cs DOT com>, John M. Aldrich <fighteer AT cs DOT com>
>> writes
>> [...]
>> >Under no circumstances should you write your program in the same
>> >directory as the system headers, nor should you copy the system headers
>> >into your program's directory.
>> [...]
>> Why not? And does this extend to .h or .hpp files one writes oneself?
>
>System headers should generally be considered part of the compiler. 
>It's considered very bad programming practice to mix them with your own
>source code, for many reasons:
>
> - Your code loses all advantages of portability, to the point of being
>totally unusable on any other compiler, or even any other computer
>running the same compiler.
> - Your code becomes extremely difficult to debug.
> - The syntax of C/C++ is designed to keep the system headers separate
>from your own by using <> brackets instead of double quotes to refer to
>them.
> - Compiler updates may change the system headers without notice,
>destroying any modifications you make and potentially overwriting your
>own code.
> - If you delete the compiler but keep your programs, you'll have to
>sort out your code from the compiler's.
>
>The proper syntax for writing programs is to refer to standard includes
>with <>, and put any definitions specific to your program in header
>files that you create yourself and refer to with "".

Thank you very much for the explanation.
>
>> I can't get RHIDE to link such .hpp files into the .cpp file in a
>> project; the linker stage simply produces crazy errors and an apparently
>> empty (but error-filled) file called: [whatever].cc. It doesn't matter
>> as I can still write, compile and link files with the same content under
>> djgpp direct in DOS. But why is this happening under the otherwise
>> excellent RHIDE?
>
>The purpose of the #include directive is to instruct the preprocessor to
>find a file and insert its code into your source.  You do NOT need to
>add header files to a project; doing so causes RHIDE to attempt to
>compile them as source code, which doesn't work and can lead to major
>errors.
I had misunderstood what projects in RHIDE were for. RHIDE tends to put
files into one project unless you tell it not to. Many thanks for
putting me straight on this.
>
>BTW, the standard extension for headers is '.h'.  '.hpp', AFAIK, is
>nonstandard, although I could be wrong.
Jesse Liberty's TYC++in24Hrs uses the .hpp suffix for files used to
store class declarations (interfaces), which the .cpp file will
#include, and which will in turn #include <iostream.h>. (This chain was
why I thought the .hpp files had to be compiled in the project). Hour 7
is where I'm at and I'll be lucky to make sense of everything first time
round!
>
Thanks a 3rd time.
Robert Christie
Spinner & Crisis, an exploration of 64-year and related cycles in history, at:
http://www.robchris.demon.co.uk/Spinner

"I may be paranoid, but that doesn't mean they're not out to get me."