Static chains and pointers to functions

Static chains and pointers to functions

[John Lu]

Hi,

I can't think of a good way to implement a call through a pointer
to a nested function, so I was wondering how gcc does it.  If the 
pointer can point to functions at different nesting levels, how is the 
static chain correctly maintained?  The only way I can think of doing
it is to use code that dynamically determines the appropriate nesting
level for the function pointer.  Is this what gcc does?

Thanks,
John Lu

P.S. The following code illustrates this situation.

void foo(int d) {
  void depth1(int c) {
    int a=1;
    void modify1() {
      a=1000;
    }
    void depth2() {
      int a=2;
      void modify2() {
	a=1000;
      }

      void end() {
	void (*f)();

	if (c==1) {
	  f=modify1;
	} else if (c==2) {
	  f=modify2;
	}
	f(); /* How is this implemented? */
      }
      end();
      printf("depth2 %d\n",a);
    }
    depth2();
    printf("depth1 %d\n",a);
  }
  
  depth1(d);
}

main() {
  foo(1);
  foo(2);
}

Re: Static chains and pointers to functions

[Fergus Henderson]

On 20-Feb-2003, John Lu <jlu@lsil.com> wrote:
> I can't think of a good way to implement a call through a pointer
> to a nested function, so I was wondering how gcc does it.

<http://gcc.gnu.org/readings.html> will point you to
<http://people.debian.org/~karlheg/Usenix88-lexic.pdf>.

-- 
Fergus Henderson <fjh@cs.mu.oz.au>  |  "I have always known that the pursuit
The University of Melbourne         |  of excellence is a lethal habit"
WWW: <http://www.cs.mu.oz.au/~fjh>  |     -- the last words of T. S. Garp.

Re: Static chains and pointers to functions

[Michael Matz]

Hi,

On Fri, 21 Feb 2003, Fergus Henderson wrote:

> <http://gcc.gnu.org/readings.html> will point you to
> <http://people.debian.org/~karlheg/Usenix88-lexic.pdf>.

Which resides now on
<http://people.debian.org/~aaronl/Usenix88-lexic.pdf> , as the first one
doesn't work anymore.


Ciao,
Michael.

Re: Static chains and pointers to functions

[Janis Johnson]

On Fri, Feb 21, 2003 at 02:44:59AM +0100, Michael Matz wrote:
> Hi,
> 
> On Fri, 21 Feb 2003, Fergus Henderson wrote:
> 
> > <http://gcc.gnu.org/readings.html> will point you to
> > <http://people.debian.org/~karlheg/Usenix88-lexic.pdf>.
> 
> Which resides now on
> <http://people.debian.org/~aaronl/Usenix88-lexic.pdf> , as the first one
> doesn't work anymore.

The link is now fixed in readings.html.

Janis