🚀 go-pugleaf

hrubin@stat.purdue.edu (Herman Rubin) writes:
>Question 1.  Is there a quick way of using a variable label?

In GCC, yes.  In standard C, no.

>The way it would be used is to identify the label to which one
>wants to transfer, and then have some other place or places 
>transfer to that point?

In standard C, you will have to use an integer variable, and
jump to a switch statement full of jumps.  Use an unsigned
int, and a compact range of numbers 0, 1, ..., n.  Many C
compilers will take
	switch (u) {
	    case 0: goto L0;
	    ...
	    case n: goto Ln;
	}
and generate code like
	load u into register
	compare u with n
	if u > n then goto Fall_Through
	goto Branch[u]
    Branch:
	.word L0
	...
	.word Ln
    Fall_Through:
	more code

This is going to cost at least
    - one unsigned comparison
    - one untaken branch
    - one load from memory
more than a Fortran-style "assigned GOTO" would.

As I said, GCC has an extension for this.

>Question 2.  Is there a way of declaring "local", so that
>labels in one block of a coding unit can be the same as
>labels in another?  The labels are within the block only,
>but the various blocks are connected with gotos, not calls.

No.  In standard C and GNU C, the scope of a label is the entire
function it's declared in.  This _does_ mean that you can jump
into a block from the outside.  Such is C.


-- 
The election is over, and Australia lost; the idjits elected _politicians_!
Richard A. O'Keefe; http://www.cs.rmit.edu.au/~ok; RMIT Comp.Sci.