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5.1.73 Pure_Barriers ¶

[GNAT] This restriction ensures at compile time that protected entry barriers are restricted to:

• components of the protected object (excluding selection from dereferences),
• constant declarations,
• named numbers,
• enumeration literals,
• integer literals,
• real literals,
• character literals,
• implicitly defined comparison operators,
• uses of the Standard.”not” operator,
• short-circuit operator,
• the Count attribute

This restriction is a relaxation of the Simple_Barriers restriction, but still ensures absence of side effects, exceptions, and recursion during the evaluation of the barriers.