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From: chris@mimsy.UUCP (Chris Torek)
Newsgroups: comp.lang.c
Subject: Re: C pointer to a function
Message-ID: <8804@mimsy.UUCP>
Date: Mon, 28-Sep-87 09:01:32 EDT
Article-I.D.: mimsy.8804
Posted: Mon Sep 28 09:01:32 1987
Date-Received: Tue, 29-Sep-87 04:26:09 EDT
References: <501@acf3.NYU.EDU>
Distribution: na
Organization: U of Maryland, Dept. of Computer Science, Coll. Pk., MD 20742
Lines: 59
Keywords: static pointer function

In article <501@acf3.NYU.EDU> hazzah@acf3.NYU.EDU (Ali Hazzah) writes:
>Consider the function foo, defined as:

>static char *foo(name)
>char *name;
>{
>	static char path[20];
>	char *strcat();
>	...
>	return(strcat(path, name));
>}

>and invoked in the following manner:

>callfoo()
>char *name;
>{
>char *path, *foo();
>...
>path = foo(name);
>...
>}

>The question here concerns the scope of the pointer to
>the function foo.

The question is ill-phrased: there is no pointer to function foo.
The only pointers declared above are pointers to char.

>Specifically, why might the pointer be defined as static?

There are two `static's in the code above.  The first is in
the declaration of function `foo',

	static char *foo(name) ...

and the second in the declaration of `path':

		static char path[20];

The two `static's have entirely different effects.  The former is
applied to a function, and all functions are static anyway:  no
function is compiled onto the run-time stack.  Outside the body of
a function, the word `static' changes meaning to `limited scope of
visibility': the function `foo' can be called only from the source
file that contains it.  The second `static' has the more expected
meaning of placing `path' in a fixed place, not on the stack; this
is done so that the value returned from function foo is not
immediately overwritten by any other stack operations.  Without
this `static', a call such as

	p = foo(name);
	printf("p = %s\n", p);

is quite likely to print rubbish, the string to which p points
having been overwritten by the call to printf().
-- 
In-Real-Life: Chris Torek, Univ of MD Comp Sci Dept (+1 301 454 7690)
Domain:	chris@mimsy.umd.edu	Path:	uunet!mimsy!chris