C function prototyping and large projects.

[Doug Philips]

LineEaterHappiness++

I've used the following method on a medium sized project that run on
PC clones under microsoft windows.  The development environment started
out as plain DOS (3.1) using MicroSoft C version 4.0.  About 3 months
into the project we switched to using the Mortice Kern systems
package (ksh, diff, awk, sed, etc.).  The microsoft compiler's ability to
generate prototypes was the only mechanism used to generate prototypes.
The underlying assumption was that the more that could be done automaticlly,
the more it would be correct.

For each source file F.c, there is a corresponding "internal
interface" file F.i, which is the prototype output of the compiler having
been run on F.c.  This file is included only by F.c.  Since the
compiler was good enough to augment the prototypes with comments that
indicate "global" functions, a simple script was used to extract the
global routine prototypes into a file called "global.rtn", which was
included by all source files.  The rationale here is that since C
would allow the function to be called anyway, it was best to make sure
the prototypes were available.  This meant adding new functions to a
modules "external interface" was as easy as adding the routine and
using it.

Since it was too agonizingly slow to always compute these files, the
makefile was doctored to break the dependency between F.c and F.i.
Everytime I knew I made an interface change I would remove the F.i
file.  The rule for generating "global.rtn" would run a script.  The
script would generate a potential new file, but install it only if it
was a change from the old version.  About once a day, sometimes twice,
I would remove all the generated files (.i, .o, etc) and let the world
rebuild just to make sure.  A good time to go get a coke, or whatever.

Since then I've read a book called "Portable C and Unix System
Programming" which had ideas similar to this.  I don't remember the
author (it's not in front of me now), but I THINK it was "Lapin".

-Doug Philips
ARPA:  Doug.Philips at k.cs.cmu.edu
-- 
Doug Philips                  "All that is gold does not glitter,
Carnegie-Mellon University       Not all those who wander are lost..."
dwp at cs.cmu.edu                     -J.R.R. Tolkien