6.8.4.1 The if statement

1732 The controlling expression of an if statement shall have scalar type.

1733 In both forms, the first substatement is executed if the expression compares unequal to 0.

1734 In the else form, the second substatement is executed if the expression compares equal to 0.

1735 If the first substatement is reached via a label, the second substatement is not executed.

1736 An else is associated with the lexically nearest preceding if that is allowed by the syntax.