Re: typedef name question

[David Fang <fang at csl dot cornell dot edu>]

>  > You are allowed to introduce identifiers in a scope that
>  > shadow identifiers outside that scope.  Even in the
>  > "foo foo;" case, where you are using an outer scope
>  > identifier and in the process are introducing a new
>  > identifier that shadows that self-same outer
>  > scope identifier.
>
> Just a small add-on:
>
> In C++ you can easily test this rule and still access the outer identifier
> by explicitly looking it up in global namespace scope. The following
> compiles with g++:
>
> // foo is defined in the global namespace
> typedef int foo;
>
> foo foo_fct(int a) {
>     foo foo;              /* line 3: a variable foo with type foo */
>     return (::foo)foo;    /* line 4: cast to outer foo */
> }
>
> Of course, this does not work with C.

One more add-on:

If you want to detect this sort of shadow-ing (as it can often reveal
programmer errors), add -Wshadow as a compile flag.  To reject it
outright, add -Werror.  (In gcc-4.2+, you'll be able to select which
warnings you want to treat as errors.)

Fang