Scopes in which __label__ can appear

[Gabriel Dos Reis]

"Zack Weinberg" <zack@codesourcery.com> writes:

[...]

| should either be ill-formed on the grounds that __label__ cannot
| appear at nested block scope other than a statement expression or
| nested function, or it should be well-formed and equivalent to
| 
| int s(int i)
| {
|   if (i > 1)  return 0;
|   if (i == 1) return 1;
|   if (i < 0)  return 2;
|   /* if (i == 0) */ return 3;
| }
| 
| but what the present compiler does is reject it on the grounds that l1
| has been defined twice.  In other words, the effect of __label__ at
| nested block scope (other than a statement expression or nested
| function) is as if the __label__ appeared at function scope.  I think
| this violates least surprise and should be changed.

On the contrary, I think is consistent with the scope of label as
defined by both C and C++ standards.  
Remember labels have function-scope.  Suddenly changing labels
(explicitly declared -- GNU extension I concede) to have a
local-scope will violates the "least surprise" principle. 

C99:
       [#3] A label name is the only kind of  identifier  that  has
       function  scope.   It  can  be  used  (in  a goto statement)
       anywhere in  the  function  in  which  it  appears,  and  is
       declared implicitly by its syntactic appearance (followed by
       a : and a statement).

C++, 3.3.4/1:
   Labels (6.1) have function scope and may be used anywhere in the
   function in which they are declared. Only labels have function scope.     


I will reject the second example on the ground that it provides two
definitions for the same label in the same (function) scope.  

-- Gaby