From owner-freebsd-arch  Fri Feb  1  6:29:38 2002
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Date: Sat, 2 Feb 2002 01:31:23 +1100 (EST)
From: Bruce Evans <bde@zeta.org.au>
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To: Juha Juntunen <estabur@hotmail.com>
Cc: <arch@FreeBSD.ORG>
Subject: Re: __P macro question
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On Fri, 1 Feb 2002, Juha Juntunen wrote:

> >>>static int  sendfile __P((struct printer *pp, int type, char *file,
> >>>                           int format));
> >>>
> >>>for a procedure declaration of:
> >>>      static int
> >>>      sendfile(pp, type, file, format)
> >>>              struct printer *pp;
> >>>              int type;
> >>>              char *file;
> >>>              char format;
> >>>      {
> >>
> >>That's *EXCATLY* why I'm converting the old, but still legal in c89,
> >>style to new style.  You get warnings that you didn't get before.
> >
> >The compiler is broken, if it accepts the second when the
> >first prototype is in scope.
> >
> >It's a broken compiler, period.
>
> How is the compiler broken, question mark.
>
> Are you perhaps objecting to the type of the last parameter
> ("int format" vs "char format")?  Please see Ansi Classic, chapter
> "3.5.4.3 Function declarators (including prototypes)", in particular
> page 69 lines 19-22.  In C99, 6.7.5.3 paragraph #11 seems to apply
> similarly.

Right.  I don't trust anyone who is not familiar with this point to
globally remove __P.

People removing __P should also be familiar with the gcc conterpoint:

    void foo(char);		/* Wrong; should be "void foo(int);". */
    void foo(c) char c; {}

gives undefined behaviour in Standard C, but gcc defines its behaviour
to be do-what-naive-programmer-expects.  This is only safe provided the
wrong prototype for foo() is always in scope before foo() is called;
otherwise foo() is sometimes passed an int and sometimes a char, but
foo() expects to be passed either an int or a char depending on whether
the wrong prototype is in scope for the function body.

Bruce


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