can you please stop sending html mails? thanks
On 2/21/13, Comeau At9Fans <comeauat9f...@gmail.com> wrote:
> On Mon, Feb 18, 2013 at 9:38 AM, Charles Forsyth
> <charles.fors...@gmail.com>wrote:
>
>> On 18 February 2013 13:02, Comeau At9Fans <comeauat9f...@gmail.com>
>> wrote:
>>
>>> seems to be doing is setting up allowing the call to compile and once
>>> that is satisfied then the subsequent definition "has" to match it, as
>>> perhaps a way to do type punning.
>>
>>
>> No, the compiler is simply applying scope rules. Without that inner
>> declaration explicitly overriding the outer declaration--whether static
>> or
>> extern is used--
>> it will not compile (eg, if you put "static void fn(Outer*);" or "extern
>> void fn(Outer*);" and remove static from fn in the file scope).
>>
>> The behaviour is undefined in ANSI C if two declarations that refer to
>> the
>> same object or function do not have compatible types
>> (normally, you're protected by another rule that you can't have
>> incompatible declarations *in the same scope*).
>>
>> ANSI C does, however, forbid the inner static declaration (which
>> surprised
>> me)
>> "The declaration of an identifier for a function that has block scope
>> shall have no explicit storage-class specifier other than extern."
>> (6.7.1)
>>
>
> We're probably saying the same thing. As you say ANSI C forbids it hence
> my comment about normally a diagnostic from a so-called mainstream
> compiler. And as you say without a declaration it would not compile
> either. The declaration should normally be in global scope (it could have
> been), which would have also produced a diagnostic since Inner/Outer don't
> match. That leaves the declaration where Eric showed it, which the Plan 9
> compiler obviously allowed. As you note the net effect is it's undefined
> (if we're using ANSI C as the metric) hence created a kind of type pun
> (even if the original code did it as a mistake).
>
> --
> Greg Comeau / 4.3.10.1 with C++0xisms now in beta!
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