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Re: Question about extern declaration

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On Sun, 18 Sep 2016 23:06:47 +0000, Kenny McCormack wrote:

> So, what, really, is the difference between the two forms (specifically,
> in an extern statement)?

One is a pointer to a pointer, the other is an array of pointers.

Arrays and pointers are equivalent in some contexts, but not all. If you
use an array as a "value", the value is a pointer to the first element.
This covers enough cases that it's not that hard to mislead yourself that
there's no difference between them.

It also doesn't help that C allows you to declare a function parameter as
an array even though what's actually being passed is a pointer. Presumably
this feature exists for "documentation", i.e. to distinguish a pointer to
a single value from a pointer to the first of many values.

The equivalence doesn't apply to any other variable declaration (extern,
"static" global, global with external linkage, "static" local, automatic
local), because in those cases you can declare variables which are
actually arrays, whereas function parameters can't be arrays.

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Question about extern declaration gazelle@shell.xmission.com (Kenny McCormack) - 2016-09-18 23:06 +0000
  Re: Question about extern declaration supercat@casperkitty.com - 2016-09-18 16:33 -0700
  Re: Question about extern declaration BartC <bc@freeuk.com> - 2016-09-19 01:02 +0100
    Re: Question about extern declaration Ben Bacarisse <ben.usenet@bsb.me.uk> - 2016-09-19 01:23 +0100
      Re: Question about extern declaration BartC <bc@freeuk.com> - 2016-09-19 10:40 +0100
  Re: Question about extern declaration m.labanowicz@gmail.com - 2016-09-19 03:27 -0700
  Re: Question about extern declaration Nobody <nobody@nowhere.invalid> - 2016-09-19 13:38 +0100
    Re: Question about extern declaration Keith Thompson <kst-u@mib.org> - 2016-09-19 11:46 -0700

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