linux-kernel - Re: [PATCH v2 2/3] lib/vsprintf: Split out sprintf() and friends

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Date:   Tue, 8 Aug 2023 08:41:49 +0200
From:   Petr Mladek <pmladek@...e.com>
To:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc:     Marco Elver <elver@...gle.com>, linux-kernel@...r.kernel.org,
        kasan-dev@...glegroups.com, linux-mm@...ck.org,
        Steven Rostedt <rostedt@...dmis.org>,
        Rasmus Villemoes <linux@...musvillemoes.dk>,
        Sergey Senozhatsky <senozhatsky@...omium.org>,
        Alexander Potapenko <glider@...gle.com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH v2 2/3] lib/vsprintf: Split out sprintf() and friends

On Mon 2023-08-07 18:13:57, Andy Shevchenko wrote:
> On Mon, Aug 07, 2023 at 06:11:24PM +0300, Andy Shevchenko wrote:
> > On Mon, Aug 07, 2023 at 06:09:54PM +0300, Andy Shevchenko wrote:
> > > On Mon, Aug 07, 2023 at 05:03:19PM +0200, Petr Mladek wrote:
> > > > On Sat 2023-08-05 20:50:26, Andy Shevchenko wrote:
> 
> ...
> 
> > > > How does this sound, please?
> > > 
> > > Not every user (especially _header_) wants to have printk.h included just for
> > > sprintf.h that may have nothing to do with real output. So, same reasoning
> > > from me as keeping that in kernel.h, i.e. printk.h no better.
> > 
> > (haven't check these, just to show how many _headers_ uses sprintf() call)
> > 
> > $ git grep -lw s.*printf -- include/linux/
> > include/linux/acpi.h
> > include/linux/audit.h
> > include/linux/btf.h
> > include/linux/dev_printk.h
> > include/linux/device-mapper.h
> > include/linux/efi.h
> > include/linux/fortify-string.h
> > include/linux/fs.h
> > include/linux/gameport.h
> > include/linux/kdb.h
> > include/linux/kdev_t.h
> > include/linux/kernel.h
> > include/linux/mmiotrace.h
> > include/linux/netlink.h
> > include/linux/pci-p2pdma.h
> > include/linux/perf_event.h
> > include/linux/printk.h
> > include/linux/seq_buf.h
> > include/linux/seq_file.h
> > include/linux/shrinker.h
> > include/linux/string.h
> > include/linux/sunrpc/svc_xprt.h
> > include/linux/tnum.h
> > include/linux/trace_seq.h
> > include/linux/usb.h
> > include/linux/usb/gadget_configfs.h
> 
> Okay, revised as my regexp was too lazy
> 
> $ git grep -lw s[^[:space:]_]*printf -- include/linux/
> include/linux/btf.h
> include/linux/device-mapper.h
> include/linux/efi.h
> include/linux/fortify-string.h
> include/linux/kdev_t.h
> include/linux/kernel.h
> include/linux/netlink.h
> include/linux/pci-p2pdma.h
> include/linux/perf_event.h
> include/linux/sunrpc/svc_xprt.h
> include/linux/tnum.h
> include/linux/usb.h
> include/linux/usb/gadget_configfs.h

This is only a tiny part of the picture.

$> git grep sc*n*printf | cut -d : -f1 | uniq | grep "\.c$" | wc -l
5254
$> find . -name  "*.c" | wc -l
32319

It means that the vsprintf() family is used in 1/6 of all kernel
source files. They would need to include one extra header.

If you split headers into so many small pieces then all
source files will start with 3 screens of includes. I do not see
how this helps with maintainability.

Best Regards,
Petr