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Groups > comp.lang.c.moderated > #521

Re: why do some writers declare and define variables separately

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On 25.10.2013 03:10, Francis Glassborow wrote:

> int i;
>
> Defines an uninitialised int (i.e. assigns storage for an int value but
> does not initialise it) and then binds the name i to that storage.

Actually that's only one of four things the above line can mean.

The above is correct only if that line appears inside a statement block. 
  In that case it defines an automatic, block-scoped, un-initializaed 
variable.

If that line appears inside a struct or union type declaration, it 
declares an element of said struct or union type.

If the same line appears outside any block, it can do one of two things:

a) it can define a variable of static duration and external linkage, 
with implied initialization to zero, or
b) it can act the same as if you had written "extern int i;", i.e. be a 
pure declaration.

The distinction between a) and b) is ruled by the somewhat complicated 
concept of a "tentative definition".
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why do some writers declare and define variables separately yoodavid <odimegwudavid@yahoo.fr> - 2013-09-18 16:42 -0500
  Re: why do some writers declare and define variables separately mt <mahdert@gmail.com> - 2013-10-03 13:37 -0500
    Re: why do some writers declare and define variables separately James Kuyper <jameskuyper@verizon.net> - 2013-10-08 16:38 -0500
      Re: why do some writers declare and define variables separately ThosRTanner <ttanner2@bloomberg.net> - 2013-10-22 16:36 -0500
        Re: why do some writers declare and define variables separately Jens Schmidt <Jens.Schmidt-HH@gmx.de> - 2013-10-24 20:10 -0500
        Re: why do some writers declare and define variables separately Francis Glassborow <francis.glassborow@btinternet.com> - 2013-10-24 20:10 -0500
          Re: why do some writers declare and define variables separately Hans-Bernhard Bröker <HBBroeker@t-online.de> - 2013-10-25 19:36 -0500

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