Also, member names are associated with the structure or union of which they are a part. The Standard puts all tags in a single name space, and also introduces a separate name space for labels see Par.A.11.1. The name spaces of identifiers are somewhat different.The scope of parameters is injected into a function's compound statement, so that variable declarations at the top level of the function cannot hide the parameters.The Standard makes it clear that the scope of such a declaration is just the block. Some implementations, when presented with an extern declaration in an inner block, would export the declaration to the rest of the file.External data declarations without any specifiers or qualifiers (just a naked declarator) are forbidden.

On the other hand, a declaration with just a structure or union tag redeclares that tag even if it was declared in an outer scope. The older style is still accepted, with restrictions. ) the notion of a function prototype declaration that incorporates the types of the parameters, and includes an explicit recognition of variadic functions together with an approved way of dealing with them.