FreeTDS Development Group

["Lowden, James K" <LowdenJK AT bernstein.com>]

> From: Craig A. Berry [mailto:craigberry AT mac.com]
> Sent: December 15, 2003 2:28 AM
>
>> I understand that using different names prevents 
>> accidentally linking in the wrong iconv functions. 
> 
> Or generating linker warnings due to a multiply defined symbol.
> 
>> OTOH, any time we use preprocessor magic, we
>> make understanding our work just that much harder.  I'm not 
>> sure what the best answer is. 
> 
> How hard is it to understand a one-line macro?   You wouldn't even
> need to understand it unless you were reading config.h to find out
> about the particulars of your environment.  We are not talking about
> an #ifdef jungle sprouting up throughout the code, we are just
> talking about a one-time preprocessor override for each function.
> 
> I hope this doesn't sound grumpy.  I've probably read the wrong
> books, listened to the wrong records, and otherwise corrupted my
> mind, but I honestly don't understand the preprocessor allergy that
> keeps popping up here, especially in light of all the other risks
> that are considered preferable.

Well, Craig, you *do* sound a little grumpy, but probably with cause.  I was
relying on my experience, which certainly doesn't encompass all linkers.
Even though no one's complained to date about linker problems with our
libiconv replacement, Frediano's choice (and your defense of it) will
probably save us headaches in the 0.62 release.  

My "allergy" to the preprocessor is based on what I think is received
wisdom, that the preprocessor requires the programmer to expand the macro in
his head in order to understand what the compiler is seeing.  That, and too
many years of C++, where I learned that the preprocessor is both bad and
obsolete.  Which it is.  ;-)

I agree, there are trade-offs, and the most convincing one you pointed out
is that linker errors almost defy human interpretation.  Anyone who can fix
a multiply defined symbol error can read (and would prefer) a macro
redefining a local name.  

Thanks for doing the research and making the case.  

Regards, 

--jkl

P.S.  Did your research say anything about the priority of object files vs.
libraries?  If you link in iconv.o, rather than iconv.a, will the linker pay
any more attention?  AFAIK, there are no standards that govern any of this;
it's just a matter of practice.  

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