An invocation of the setjmp macro shall appear only in one of the following contexts:
— the entire controlling expression of a selection or iteration statement;
— one operand of a relational or equality operator with the other operand an integer
constant expression, with the resulting expression being the entire controlling
expression of a selection or iteration statement;
— the operand of a unary ! operator with the resulting expression being the entire
controlling expression of a selection or iteration statement; or
— the entire expression of an expression statement (possibly cast to void).