5.8 Goto Statements

danger

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1

[A goto_statement specifies an explicit transfer of control from this statement to a target statement with a given label.]

Syntax

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goto_statement ::= goto label_name;

Name Resolution Rules

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The label_name shall resolve to denote a label; the statement with that label is the target statement.

Legality Rules

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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

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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.

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NOTE 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

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Example of a loop containing a goto statement:

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<<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;