Re: [PATCH 00/12] Clang -Wformat warning fixes

[Joe Perches]

On Fri, 2022-06-10 at 07:20 +0200, Greg Kroah-Hartman wrote:
> On Thu, Jun 09, 2022 at 04:16:16PM -0700, Bill Wendling wrote:
> > On Thu, Jun 9, 2022 at 4:03 PM Jan Engelhardt <jengelh@xxxxxxx> wrote:
> > > On Friday 2022-06-10 00:49, Bill Wendling wrote:
> > > > On Thu, Jun 9, 2022 at 3:25 PM Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> wrote:
> > > > > On Thu,  9 Jun 2022 22:16:19 +0000 Bill Wendling <morbo@xxxxxxxxxx> wrote:
> > > > > 
> > > > > > This patch set fixes some clang warnings when -Wformat is enabled.
> > > > > 
> > > > > tldr:
> > > > > 
> > > > > -       printk(msg);
> > > > > +       printk("%s", msg);
> > > > > 
> > > > > Otherwise these changes are a
> > > > > useless consumer of runtime resources.

> > > > Calling a "printf" style function is already insanely expensive.

I expect the printk code itself dominates, not the % scan cost.

> > > Perhaps you can split vprintk_store in the middle (after the call to
> > > vsnprintf), and offer the second half as a function of its own (e.g.
> > > "puts"). Then the tldr could be
> > > 
> > > - printk(msg);
> > > + puts(msg);
> > 
> > That might be a nice compromise. Andrew, what do you think?
> 
> You would need to do that for all of the dev_printk() variants, so I
> doubt that would ever be all that useful as almost no one should be
> using a "raw" printk() these days.

True.  The kernel has ~20K variants like that.

$ git grep -P '\b(?:(?:\w+_){1,3}(?:alert|emerg|crit|err|warn|notice|info|cont|debug|dbg)|printk)\s*\(".*"\s*\)\s*;' | wc -l
21160

That doesn't include the ~3K uses like

#define foo "bar"
	printk(foo);

$ git grep -P '\b(?:(?:\w+_){1,3}(?:alert|emerg|crit|err|warn|info|notice|debug|dbg|cont)|printk)\s*\((?:\s*\w+){1,3}\s*\)\s*;'|wc -l
2922

There are apparently only a few hundred uses of variants like:

	printk("%s", foo)

$ git grep -P '\b(?:(?:\w+_){1,3}(?:alert|emerg|crit|err|warn|info|notice|debug|dbg|cont)|printk)\s*\(\s*"%s(?:\\n)?"\s*,\s*(?:".*"|\w+)\s*\)\s*;' | wc -l
305

unless I screwed up my greps (which of course is quite possible)