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From: Keith Thompson <kst-u@mib.org>
Newsgroups: comp.lang.c
Subject: Re: C Translator
Date: Thu, 28 Mar 2019 19:02:33 -0700
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Bart <bc@freeuk.com> writes:
[...]
> Here are some weird constructs that I didn't know you could do:
>
>        switch (len & 31) {
>          do {
>            case  0: dest[pos -  1] = src[pos -  1];
>            case 31: dest[pos -  2] = src[pos -  2];
>            ....
>            case  2: dest[pos - 31] = src[pos - 31];
>            case  1: dest[pos - 32] = src[pos - 32];
>          } while ((pos -= 32) != 0);

Do a web search for "Duff's Device".

[SNIP]

> Compared to those, this is nothing:
>
>     extern fn(void) {....}

Missing return type.  Are you compiling in C90 mode, or did you just
leave it out?

> A function is marked as 'extern', but is defined here anyway. Since such 
> a definition must only be visible in one module, what is the point of 
> 'extern'?

The syntax for an function-definition permits a storage-class-specifier.
A constraint requires it to be either "extern" or "static" (6.9.1p4).

A function-definition has external linkage by default.  Adding the
"extern" keyword is redundant but harmless (like adding "auto" to a
block-scope object declaration).  Which means that you can declare it
and refer to it in another translation unit.  (With "static" you
couldn't do that.)

> (Apparently the point is that there is a macro added to the start of 
> both a function declaration AND its definition, and that macro happens 
> to include 'extern'. That no one will ever see 'extern' because it's 
> hidden, doesn't matter. This sort of goings on doesn't seem to be meant 
> for anyone to read.)

Did this inconvenience you in some way?  Did you implement your own C
compiler without paying attention to the C standard?

> Can anyone blame me for considering C a crude language little different 
> from assembly? In assembly, also, you can write chaotic code with no 
> logical structure.

I don't blame you for considering it any way you like.  I do blame you
for endlessly whining about it.

-- 
Keith Thompson (The_Other_Keith) kst-u@mib.org  <http://www.ghoti.net/~kst>
Will write code for food.
void Void(void) { Void(); } /* The recursive call of the void */