Constants in conditionals

[Paul Tomblin]

jef at well.sf.ca.us (Jef Poskanzer) writes:

>In the referenced message, pt at geovision.gvc.com wrote:
>}Sorry, but #ifdef or #if is SOOO basic, that if you don't know how to use
>}it (or refuse to for wierd reasons), you loose.

>Using "if" for conditional compilation instead of "#if" has one major
>advantage: the outshipped code continues to get checked for syntax
>errors.  For machine-dependent code you probably don't want this,
>otherwise you probably do.  But you're right, you do have to check
>the generated assembly code to make sure your compiler is doing
>the right thing.  These days, most do.

I think you'd be making a mistake in assuming that because code still
compiles without error that it is still correct.  "If it's not exercised,
it's not correct" is a good assumption that any future maintainer of the code
would have to make.  Code around here that is "#if 0"ed out, is usually
expunged the next time a bug shows up it that area of code.  If it's 
"if (FALSE)"ed out, it will be expunged the first time it's spotted. 
(And the coder will get a talking to!  PCC doesn't do the right thing.)

We use #ifdef for two reasons: Machine dependant code, and debugging. 
When trying out new things, or temporarily removing something to try
another approach, we tend to put in #ifdefs, but we try and remove them
when we are done.  Anything else is asking for maintainence headaches.
(I know, I'm in charge of maintainence!)
-- 
Paul Tomblin, Department of Redundancy Department.       ! My employer does 
The Romanian Orphans Support Group needs your help,      ! not stand by my
Ask me for details.                                      ! opinions.... 
pt at geovision.gvc.com or {cognos,uunet}!geovision!pt      ! Me neither.