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From: karl@haddock.ISC.COM (Karl Heuer)
Newsgroups: comp.lang.c
Subject: Re: goto's and switch statements -- mild proposal
Message-ID: <930@haddock.ISC.COM>
Date: Wed, 12-Aug-87 17:23:26 EDT
Article-I.D.: haddock.930
Posted: Wed Aug 12 17:23:26 1987
Date-Received: Sat, 15-Aug-87 02:21:10 EDT
References: <855@tjalk.cs.vu.nl> <2683@hoptoad.uucp> <916@haddock.ISC.COM> <1032@ius1.cs.cmu.edu>
Reply-To: karl@haddock.ima.isc.com (Karl Heuer)
Organization: Interactive Systems, Boston
Lines: 25

[Context: karl@haddock suggested that switch labels should behave more like
normal labels; and that the latter should have to be declared, giving them
block scope; and a bunch of related ideas.]

In article <1032@ius1.cs.cmu.edu> edw@ius1.cs.cmu.edu (Eddie Wyatt) writes:
>Consider the problems "goto case N" cause when there are two switch
>statements each with a case N label in the function block.

The solution is for the scope of a switch label to be the switch statement
itself.  Thus in the example posted in another article by ron@topaz, you get
an error message from the compiler.  If the switch statements are nested, you
get the innermost enclosing one.

>Also just consider how you would implement the two switch statements each
>with a case N label.  Since each label is a posible target of a goto, it must
>be put into a label table for that function block.  Now you have multiple
>defined labels (label N) unless you do a few ugly things to uniquely define
>each label - but then look up on labels become more expensive.

I don't see that this is any worse than the current situation with variables:
"{ int i; ... { double i; ... i=0; } }".  In fact, by removing the special
case (currently, labels are the only things that have function scope) it's
possible that this would simplify the compiler.

Karl W. Z. Heuer (ima!haddock!karl or karl@haddock.isc.com), The Walking Lint