5.8 Goto Statements
1
[A goto_statement specifies
an explicit transfer of control from this statement
to a target statement with a given label.]
Syntax
2
goto_statement ::= goto label_name;
Name Resolution Rules
3
{target statement
(of a goto_statement)} The
label_name
shall resolve to denote a
label; the
statement
with that
label is the
target statement.
Legality Rules
4
The innermost sequence_of_statements
that encloses the target statement shall also enclose the goto_statement.
Furthermore, if a goto_statement is enclosed
by an accept_statement or a body, then the
target statement shall not be outside this enclosing construct.
4.a
Ramification: The goto_statement
can be a statement of an inner sequence_.
4.b
It follows from the second rule that if the
target statement is enclosed by such a construct,
then the goto_statement cannot be outside.
Dynamic Semantics
5
{execution (goto_statement)
[partial]} The execution of a
goto_statement
transfers control to the target statement, completing the execution of
any
compound_statement that encloses the
goto_statement
but does not enclose the target.
6
10 The above rules allow transfer of control
to a statement of an enclosing sequence_of_statements
but not the reverse. Similarly, they prohibit transfers of control such
as between alternatives of a case_statement,
if_statement, or select_statement;
between exception_handlers; or from an exception_handler
of a handled_sequence_of_statements back to
its sequence_of_statements.
Examples
7
Example of a loop
containing a goto statement:
8
<<Sort>>
for I in 1 .. N-1 loop
if A(I) > A(I+1) then
Exchange(A(I), A(I+1));
goto Sort;
end if;
end loop;
Sponsored by Ada-Europe