Martin v. Löwis wrote: > David Abrahams schrieb: > >>(C++ allows restating of typedefs; if C allows it, that should be >>something like): > > C also allows this; [...] This is nitpicking, since you agreed the change to the PEP, but are you sure that C allows this? From C99 + TC1 + TC2 (http://www.open-std.org/JTC1/SC22/WG14/www/standards): # 6.2.2 Linkages of identifiers # # 6 The following identifiers have no linkage: an identifier declared # to be anything other than an object or a function; [...] (i.e. typedef identifiers have no linkage) # 6.7 Declarations # # Constraints # 3 If an identifier has no linkage, there shall be no more than one # declaration of the identifier (in a declarator or type specifier) # with the same scope and in the same name space, except for tags as # specified in 6.7.2.3. # 6.7.2.3 Tags # # Constraints # 1 A specific type shall have its content defined at most once. (There is nothing else in 6.7.2.3 that applies to typedefs.) Since 6.7 (3) and 6.7.2.3 (1) are constraints, I read this as saying that a C99 implementation must produce a diagnostic if a typedef is redeclared in the same scope. If the program is run despite the diagnostic, its behaviour is undefined. Several C compilers I've used in the past have needed the idempotence guard on typedefs, in any case. -- David Hopwood <david.nospam.hopwood at blueyonder.co.uk>
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