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From: Keith Thompson <kst-u@mib.org>
Newsgroups: comp.lang.c
Subject: Re: Compiler design in C?
Date: Thu, 10 Nov 2016 13:35:32 -0800
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jacobnavia <jacob@jacob.remcomp.fr> writes:
> Le 10/11/2016 à 21:57, Gareth Owen a écrit :
>> I actually considered mentioning this, but decided against it.
>
> And the reason was?
>
> Why is the pre-processor such an "evil"?
>
> Look at this for instance: (this is the "valarraygen.c file of the ccl)
>
>    81 static int ResizeTo(ValArray *AL,size_t newcapacity)
>    82 {
>    83     ElementType *oldcontents;
>    84
>    85     if (AL->capacity == newcapacity) return 0;
>    86     oldcontents = AL->contents;
>    87     AL->contents = AL->Allocator->realloc(AL->contents,newcapacity
>                           * sizeof(ElementType));
>    88     if (AL->contents == NULL) {
>    89         AL->contents = oldcontents;
>    90         return NoMemory("ResizeTo");
>    91     }
>    92     AL->capacity = newcapacity;
>    93     AL->timestamp++;
>    94     return 1;
>    95 }
>
> ElementType is a macro. A plain #define with the name of the underlying 
> type.
>
> I find it OK, you can do a lot of things with the preprocessor.

I'm probably missing some context here, but what is the advantage of
making ElementType a macro rather than a typedef?

In particular, if ElementType is `int[3]`, then
    ElementType *oldcontents;
is a syntax error.

-- 
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"