(j3.2006) GOTO label - with label in BLOCK and in inclusive scope

[Rasmussen, Craig E]

Bill's answer is the way I would hope the code would work also.

-craig

On Aug 18, 2011, at 10:23 AM, Bill Long wrote:

> 
> 
> On 8/18/11 7:35 AM, Tobias Burnus wrote:
>> Dear all,
>> 
>> I was wondering whether the following program is valid - and, if so, to
>> which label jumps the goto?
>> 
>>     block
>>       goto 1
>>       stop "one"
>> 1    continue
>>        stop "two"
>>     end block
>> 1  continue
>>      stop "three"
>> end
>> 
> 
> The code compiles for me and executes as
> 
>> ./a.out
>  STOP two
> 
> which indicates that the "local" label 1 wins as the target of the goto. 
>   But it sure LOOKS confusing in a small program like this.  All sorts 
> of obfuscated Fortran opportunities come to mind...  On the other hand, 
> the point of BLOCK constructs is to write code with localized variables 
> that is non-disruptive to the surrounding environment.  In a larger 
> code, the ability to have non-colliding statement labels would be valuable.
> 
> Cheers,
> Bill
> 
> 
>> 
>> The programs seems to be valid as the following is fulfilled:
>> 
>> "The same statement label shall not be given to more than one statement
>> in its scope." (F2008, "3.2.5 Statement labels")
>> 
>> And BLOCK is a scoping unit of its own: "1.3.124  scoping unit.  BLOCK
>> construct, derived-type definition, interface body, program unit, or
>> subprogram, excluding all nested scoping units in it."
>> 
>> And "8.2 Branching" tells me:
>> "A branch causes a transfer of control from one statement to a labeled
>> branch target statement in the same inclusive scope."
>> 
>> Plus for GOTO (R851):
>> "C846 (R851) The label shall be the statement label of a branch target
>> statement that appears in the same inclusive scope as the goto-stmt."
>> 
>> with
>> 
>> "1.3.87  inclusive scope.  nonblock scoping unit plus every block
>> scoping unit whose host is that scoping unit or that is nested within
>> such a block scoping unit
>> NOTE 1.5
>> That is, inclusive scope is the scope as if BLOCK constructs were not
>> scoping units."
>> 
>> 
>> Thus, also the GOTO seems to be valid. However, to which label does the
>> GOTO jump to?
>> 
>> Tobias
>> _______________________________________________
>> J3 mailing list
>> J3 at j3-fortran.org
>> http://j3-fortran.org/mailman/listinfo/j3
> 
> -- 
> Bill Long                                           longb at cray.com
> Fortran Technical Support    &                 voice: 651-605-9024
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