Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!tut.cis.ohio-state.edu!MCC.COM!rfg
From: rfg@MCC.COM (Ron Guilmette)
Newsgroups: gnu.gcc
Subject: address of labels
Message-ID: <8904282319.AA08492@riunite.aca.mcc.com>
Date: 28 Apr 89 23:19:19 GMT
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It is apparent that C is being used more and more as a kind of high-level
assembly language.

GCC supports this kind of usage quite well in general.  The embedded
assembly language features of GCC are especially helpful in such
applications.

Of course it is the C language itself, and specifically its closeness
to typical hardware that is the real important thing in such situations.
I find that I can typically do better that 95% of even very low level
coding (e.g. diagnostics and boot code) in C.

One blatantly obvious feature seems to be missing however; i.e. the
ability to take the address of a label.  Is there some way of doing
this in GCC that I don't know about?  I'd like to be able to
construct things like jump tables mostly in C, but I can't for the
life of me see how to do it without being able to say something like:

int my_func ()
{
	static void* jump_table[] = { &label0, &label1, &label2 };

label0:
	...

label1:
	...

label2:
	...
}

Now I know that somebody will say that this is just a switch statement
and that I should use that, but I have other uses of label addresses in
mind also.  For instance, I'd like to be able to have a mechanism for
expressing things like Ada-style exception handling, e.g.:

void my_function ()
{
	declare_handler (&exception_handler);

	...

	deactivate_handler ();
	return;

exception_handler:
	deactivate_handler ();
	...
	return;
}