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From: john@auspyr.UUCP (John Weald)
Newsgroups: comp.lang.c
Subject: Scope of externals definitions
Message-ID: <8959@auspyr.UUCP>
Date: Tue, 8-Sep-87 13:52:21 EDT
Article-I.D.: auspyr.8959
Posted: Tue Sep  8 13:52:21 1987
Date-Received: Thu, 10-Sep-87 05:39:27 EDT
Reply-To: john@auspyr.UUCP (John Weald)
Organization: Austec, Inc. San Jose
Lines: 53


What does the dpANSI standard have to say about the following?

The following program compiles (does not link of course) on 3b5 SVR2:

In the file foo.c:

main()
{
	extern int foo;

	foo++;

	f();
}

f()
{
	/* Same "foo" as above */
	foo++;
}

K&R have this to say on the subject:

Page 76, section 4.5 "Scope Rules":
	The scope of an external variable lasts from the point at which it
	is declared in a source file to the end of that file. ...
		(Some discussion about declarations deleted)
	On the other hand, the lines
		extern int sp;
		extern double val[];
	*declare* for the rest of the file that sp is an int and that
	val is a double array.

Page 206, section 11.1 "Lexical Scope":
	The lexical scope of identifiers declared in external definitions
	persists from the definition through the end of the source file
	in which they appear.


On our uVAX running VMS 4.5 (C v2.3) the variable "foo" only has scope
within the function block. It gives the message:

	"foo" is not declared within the scope of this usage


The key words appear to be "though the end of the file."

Any comments?

John Weald,	Austec, Inc.	San Jose.
-- 
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