Re: Concatenated if and preprocessor

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Sujet : Re: Concatenated if and preprocessor
De : jameskuyper (at) *nospam* alumni.caltech.edu (James Kuyper)
Groupes : comp.lang.c
Date : 13. Mar 2025, 17:07:05
Autres entêtes
Organisation : A noiseless patient Spider
Message-ID : <vqv0ia$3g4dg$1@dont-email.me>
References : 1
User-Agent : Mozilla Thunderbird
On 3/13/25 11:44, pozz wrote:
Consider this code:
 
if (cond1) {
...
} else if (cond2) {
...
} else if (cond3) {
...
}
 
I want to activate every single if with a macro preprocessor. All the
combinations are possible: only the first, only the second, only the
third, the first and second... and so on.
 
What's the best method to have a clean code that is always compiled
without errors?

The cleanest way to do this involves trusting the compiler to quietly
remove unused branches:

#ifdef COND1
    if (cond1) }
    } else
#endif

#ifdef COND2
    if (cond2) {
    } else
#endif

#ifdef COND3
    if (cond3 ) {
    }
#else
    ; // Alternatively, use {}
#endif

Date Sujet#  Auteur
13 Mar 25 * Concatenated if and preprocessor26pozz
13 Mar 25 +- Re: Concatenated if and preprocessor1David Brown
13 Mar 25 +- Re: Concatenated if and preprocessor1James Kuyper
13 Mar 25 +- Re: Concatenated if and preprocessor1Kaz Kylheku
13 Mar 25 +- Re: Concatenated if and preprocessor1bart
13 Mar 25 +* Re: Concatenated if and preprocessor3Tim Rentsch
14 Mar 25 i`* Re: Concatenated if and preprocessor2Lynn McGuire
14 Mar 25 i `- Re: Concatenated if and preprocessor1Tim Rentsch
13 Mar 25 +- Re: Concatenated if and preprocessor1James Kuyper
14 Mar 25 `* Re: Concatenated if and preprocessor17pozz
14 Mar 25  +- Re: Concatenated if and preprocessor1David Brown
14 Mar 25  +- Re: Concatenated if and preprocessor1Dan Purgert
14 Mar 25  +* Re: Concatenated if and preprocessor12Tim Rentsch
14 Mar 25  i`* Re: Concatenated if and preprocessor11Richard Harnden
14 Mar 25  i +* Re: Concatenated if and preprocessor9Tim Rentsch
14 Mar 25  i i`* Re: Concatenated if and preprocessor8Keith Thompson
14 Mar 25  i i +* Re: Concatenated if and preprocessor3Richard Harnden
14 Mar 25  i i i`* Re: Concatenated if and preprocessor2Tim Rentsch
15 Mar 25  i i i `- Re: Concatenated if and preprocessor1David Brown
14 Mar 25  i i +* Re: Concatenated if and preprocessor3Tim Rentsch
15 Mar 25  i i i`* Re: Concatenated if and preprocessor2Keith Thompson
15 Mar 25  i i i `- Re: Concatenated if and preprocessor1Tim Rentsch
15 Mar 25  i i `- Re: Concatenated if and preprocessor1David Brown
15 Mar 25  i `- Re: Concatenated if and preprocessor1Lawrence D'Oliveiro
14 Mar 25  +- Re: Concatenated if and preprocessor1Keith Thompson
15 Mar 25  `- Re: Concatenated if and preprocessor1James Kuyper

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