Re: [avr-gcc-list] Best practice for external variable (newbie-ish question)

[David Kelly]

On Nov 20, 2005, at 1:16 AM, Joerg Wunsch wrote:

> As Russell already mentioned, the best way to maintain that is by
> placing a single declaration of the variable into a central header
> file that is included from all source files.

Or in the event all the functions that need to access the global  
variable are in the same source file just drop the whole "extern"  
thing and simply declare the variable outside of a function before  
its first use. Then don't bother to restate it as "extern" inside a  
function because as you have already demonstrated that method is  
prone to error, and because the function already knows about that  
variable.

The only time I use "extern" is for prototyping in #include files.  
Even so, the variable has to be declared somewhere without "extern"  
and outside of a function in order to create the allocation. Make  
sure you #include the prototype file in the source file which creates  
the storage for the variable because avr-gcc will bellyache if the  
two do not match. This is one of the ways one makes the compiler  
double-check one's work.

--
David Kelly N4HHE, address@hidden
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Whom computers would destroy, they must first drive mad.