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From: ron@argus.UUCP (Ron DeBlock)
Newsgroups: comp.sys.atari.st
Subject: Re: C question
Summary: static, extern, auto
Message-ID: <1381@argus.UUCP>
Date: 6 Dec 89 17:45:24 GMT
References: <8912050802.AA12717@ucbvax.Berkeley.EDU> <875@lzaz.ATT.COM> <74734@tut.cis.ohio-state.edu>
Reply-To: ron@argus.UUCP (Ron DeBlock)
Organization: NJ Inst of Tech, Newark NJ
Lines: 56

Someone asked why
	main()
	{
		char fred[] = "hello";
		....
won't work, and a bunch of answers followed.  Some made no sense, others
were close, but I haven't seen the complete answere yet.  So here it is:


The error from the compiler on this line is probably something like:
	"No initialization of automatic agragate."

This means that an aggragate structure (an arry, struct or union) that is
automatically allocat cannot be pre-initialized.  Automatics are any
variables declared INSIDE of a function (this excludes the functions 
arguments).  For non-aggragate variables, (int, *, cha the compiler
will generate storage and code to initialize.  It does not do so for
aggragates.

The solution is to make the variable non-automatic.  Someone mentioned
declaring the array as 
	static char fred[]
which will work just fine.  Global variables are also not automatic,
so moving the declaration outside of main() will also work.

C provides the keyword "auto" to make variables automatic.  I've
never seen it used, since it is only valid within functi (or block)
scope and it is the default.

The "static" keyword has an interesting side effect: a global symbol
declared as static only has file scope.  This allows you to create
global vaiables and functions which are visible only within a file:

	static int foo;
	int bar;

	static int bas()
	{
		...
	}

	int baf()
	{
		...
	}



baf() and bar may be declareas extern in other files and used normally.
However, foo and bas() CANNOT be referenced outside of the file!  This is 
sometimes useful if you want to be sure that certain variables or functions
cannot be accessed from other code.
-- 
Ron DeBlock	N2JSO
Net: ...!rutgers!galaxy!argus
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