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From: Keith Thompson <kst-u@mib.org>
Newsgroups: comp.lang.c
Subject: Re: Set the result of void function
Date: Thu, 28 Sep 2017 09:25:25 -0700
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Xref: csiph.com comp.lang.c:120454

Malcolm McLean <malcolm.arthur.mclean@gmail.com> writes:
[...]
> Consider this
>
> /*
>    DNA base pairing partner
> */
> char partner(char base)
> {
>    switch(base)
>    {
>       case 'A' : return 'T';
>       case 'C' : return 'G';
>       case 'G': return 'C':
>      case 'T': return 'A':
>      default: assert(0);
>    }
> }
>
> The function cannot legitimately be called with anything other
> than one of the four DNA bases. But it isn't clear what it should
> do if assertions are turned off. Returning garbage is probably
> a reasonable answer. If we return 0 people might start relying
> on the behaviour and mis-use the function as an "isDNABase().

I might consider adding `return '?';` after the assert, so that
when NDEBUG is defined errors show consistent symptoms.  Seeing '?'
in the output is a clue that soomething is wrong.

On the other hand, leaving off the return means that a sufficiently
clever compiler might be able to diagnose some such errors at compile
time.

-- 
Keith Thompson (The_Other_Keith) kst-u@mib.org  <http://www.ghoti.net/~kst>
Working, but not speaking, for JetHead Development, Inc.
"We must do something.  This is something.  Therefore, we must do this."
    -- Antony Jay and Jonathan Lynn, "Yes Minister"