Re: header files including other files

On Thu, 06 Sep 2007 22:37:34 +0000, Peter Harrison wrote:

Sorry if this is out of place here. Comp.lang.C would probably be better
but I left my flameproof underwear at work.

Really I guess I am asking advice about source code organisation.

I have a C langage project - a small robot. I want to use the various
types defined in stdint.h such as uint8_t, uint16_t and so on as I
expect the code to get ported to other processors.

Now, in any particular module, the module header file declares exported
functions and variables and so needs to know the types. Is it considered
acceptable to include the stdint.h header in the module header or is it
better to include it in the source code. Now I have written it out loud,
I suppose the latter is best as the header file never gets compiled,
just included with other compilation units.

In a similar vein, the hardware definitions for the location of the
buttons, LEDs, motor drivers etc all live in a single header file called
hardware.h. In here, I have included the processor definitions header as
the actual names of the ports and pins are closely dependent upon the
actual processor used. This is the only place in the project where the
processor header is included. Is it better to do this?

I would be grateful for anyone who can point me at a good resource
recommeding how best to organize modules and their headers. From a lot
of browsing about, everyone semms to just do their own thing but there
must be good and bad practice out there to learn from.

Pete

Unless you are doing something _very_ weird you should _always_ include
predecessor header files in successor header files. Your header files
should be designed so that you can plop one into an empty "C" file and
compile it with no errors. Furthermore, they should be designed so that
you can put them into a "C" file in any order and have a successful,
predictable compile.

So the other thing you should do is guard the contents of your header
file. So, for instance, at the start of header.h you should have

/////////////////////////
// file: header.h
// -- etc --
//

#ifndef HEADER_H
#define HEADER_H

// (put your header stuff here)

#endif // HEADER_H

If you don't do this, then the second time the compiler encounters
header.h (because you've included it everywhere) all hell will break loose.

--
Tim Wescott
Control systems and communications consulting
http://www.wescottdesign.com

Need to learn how to apply control theory in your embedded system?
"Applied Control Theory for Embedded Systems" by Tim Wescott
Elsevier/Newnes, http://www.wescottdesign.com/actfes/actfes.html
.