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On Thu, Feb 21, 2013 at 10:13 AM, hiro <23h...@gmail.com> wrote: > 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! >> Comeau C/C++ ONLINE ==> http://www.comeaucomputing.com/tryitout >> World Class Compilers: Breathtaking C++, Amazing C99, Fabulous C90. >> Comeau C/C++ with Dinkumware's Libraries... Have you tried it? >> >
