Date:   Mon, 6 Dec 2021 19:55:26 +0000
From:   Matthew Wilcox <willy@infradead.org>
To:     Nick Desaulniers <ndesaulniers@google.com>
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Miguel Ojeda <miguel.ojeda.sandonis@gmail.com>,
        Miguel Ojeda <ojeda@kernel.org>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        rust-for-linux <rust-for-linux@vger.kernel.org>,
        Linux Kbuild mailing list <linux-kbuild@vger.kernel.org>,
        Linux Doc Mailing List <linux-doc@vger.kernel.org>,
        linux-kernel <linux-kernel@vger.kernel.org>,
        Gary Guo <gary@garyguo.net>,
        Alex Gaynor <alex.gaynor@gmail.com>,
        Wedson Almeida Filho <wedsonaf@google.com>
Subject: Re: [PATCH 11/19] vsprintf: add new `%pA` format specifier
Message-ID: <Ya5qrjabKMM6sPr+@casper.infradead.org>
References: <20211206140313.5653-1-ojeda@kernel.org>
 <20211206140313.5653-12-ojeda@kernel.org>
 <Ya4mAqoOa8zIeZGZ@kroah.com>
 <CANiq72kCmLgrv++mFygR6dt0xOhfv04o9j6jYLQ1N+zLNvqohQ@mail.gmail.com>
 <Ya40Bcv+eFkqc9jv@kroah.com>
 <CAKwvOdkLF_DPP1FF60720q3zxZG2qaSNTthxJPxLb4Bj=AFE=Q@mail.gmail.com>
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On Mon, Dec 06, 2021 at 11:52:09AM -0800, Nick Desaulniers wrote:
> On Mon, Dec 6, 2021 at 8:14 AM Greg Kroah-Hartman
> <gregkh@linuxfoundation.org> wrote:
> >
> > On Mon, Dec 06, 2021 at 04:56:32PM +0100, Miguel Ojeda wrote:
> > > On Mon, Dec 6, 2021 at 4:46 PM Greg Kroah-Hartman
> > > <gregkh@linuxfoundation.org> wrote:
> > > >
> > > > That should be in a .h file somewhere.  Remember, don't put #ifdef in .c
> > > > files please.
> 
> Why not put #ifdef in .c files?
> 
> > > Will do, thanks for reviewing!
> > >
> > > > Same here, this should not be needed if you put it in a .h file
> > > > correctly.
> 
> I guess IS_ENABLED could be used in the .c code, but I don't see how
> they could move the dispatch to rust_fmt_argument to a header without
> moving the definition of pointer() to a header, which they probably
> _cant_ do because it's noinline_for_stack.

In the header file, you put:

#ifdef CONFIG_FOO
int foo(void);
#else
static inline int foo(void) { }
#endif

and then in your .c file, you call foo() unconditionally, and everything
works beautifully.