[stmt.iter.general] (original) (raw)

8 Statements [stmt]

8.6 Iteration statements [stmt.iter]

8.6.1 General [stmt.iter.general]

Iteration statements specify looping.

The substatement in an iteration-statement implicitly defines a block scope which is entered and exited each time through the loop.

If the substatement in an iteration-statement is a single statement and not a compound-statement, it is as if it was rewritten to be a compound-statement containing the original statement.

[Example 1:

while (--x >= 0) int i;can be equivalently rewritten aswhile (--x >= 0) { int i;}

Thus after the while statement, i is no longer in scope.

— _end example_]

A trivial infinite loop is a trivially empty iteration statement for which the converted controlling expression is a constant expression, when interpreted as a constant-expression ([expr.const]), and evaluates to true.

The statement of a trivial infinite loop is replaced with a call to the function std​::​this_thread​::​yield ([thread.thread.this]); it is implementation-defined whether this replacement occurs on freestanding implementations.

[Note 2:

In a freestanding environment, concurrent forward progress is not guaranteed; such systems therefore require explicit cooperation.

A call to yield can add implicit cooperation where none is otherwise intended.

— _end note_]