linux-kernel - Re: [PATCH 5/5] media: atomisp: get rid of -Wsuggest-attribute=format warnings

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Message-ID: <20200903162751.1dd13300@coco.lan>
Date:   Thu, 3 Sep 2020 16:27:51 +0200
From:   Mauro Carvalho Chehab <mchehab+huawei@...nel.org>
To:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc:     Sakari Ailus <sakari.ailus@...ux.intel.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-media@...r.kernel.org, devel@...verdev.osuosl.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 5/5] media: atomisp: get rid of
 -Wsuggest-attribute=format warnings

Em Thu, 3 Sep 2020 17:07:24 +0300
Andy Shevchenko <andriy.shevchenko@...ux.intel.com> escreveu:

> On Thu, Sep 03, 2020 at 03:57:32PM +0200, Mauro Carvalho Chehab wrote:
> > There are some warnings reported by gcc:
> > 	drivers/staging/media/atomisp//pci/atomisp_compat_css20.c:164:2: warning: function ‘atomisp_css2_dbg_print’ might be a candidate for ‘gnu_printf’ format attribute [-Wsuggest-attribute=format]
> > 	drivers/staging/media/atomisp//pci/atomisp_compat_css20.c:170:2: warning: function ‘atomisp_css2_dbg_ftrace_print’ might be a candidate for ‘gnu_printf’ format attribute [-Wsuggest-attribute=format]
> > 	drivers/staging/media/atomisp//pci/atomisp_compat_css20.c:170:2: warning: function ‘atomisp_css2_dbg_ftrace_print’ might be a candidate for ‘gnu_printf’ format attribute [-Wsuggest-attribute=format]
> > 	drivers/staging/media/atomisp//pci/atomisp_compat_css20.c:176:2: warning: function ‘atomisp_css2_err_print’ might be a candidate for ‘gnu_printf’ format attribute [-Wsuggest-attribute=format]
> > 
> > That are due to the usage of printf-like messages without
> > enabling the error checking logic.
> > 
> > Add the proper attributes in order to shut up such warnings.  
> 
> > +static int  __attribute__((format (printf, 1, 0)))
> > +atomisp_css2_dbg_ftrace_print(const char *fmt, va_list args)
> >  {
> >  	ftrace_vprintk(fmt, args);
> >  	return 0;
> >  }
> >    
> 
> Why not to drop it completely as well?

Because of this:

	make -s CC="gcc -fno-diagnostics-show-caret" CF=-D__CHECK_ENDIAN__ CONFIG_DEBUG_SECTION_MISMATCH=y  W=1 M=drivers/staging/media/atomisp/ 2>&1|grep -v ": In function ‘"
	drivers/staging/media/atomisp//pci/atomisp_compat_css20.c:858:52: error: ‘ftrace_vprintk’ undeclared (first use in this function); did you mean ‘tracepoint’?
	drivers/staging/media/atomisp//pci/atomisp_compat_css20.c:858:52: note: each undeclared identifier is reported only once for each function it appears in

Basically, kernel.h defines it as a macro:

	#define ftrace_vprintk(fmt, vargs)					\
	do {									\
		if (__builtin_constant_p(fmt)) {				\
			static const char *trace_printk_fmt __used		\
			  __attribute__((section("__trace_printk_fmt"))) =	\
				__builtin_constant_p(fmt) ? fmt : NULL;		\
										\
			__ftrace_vbprintk(_THIS_IP_, trace_printk_fmt, vargs);	\
		} else								\
			__ftrace_vprintk(_THIS_IP_, fmt, vargs);		\
	} while (0)

Now, a different thing would be to get rid of using trace as a debug
mechanism. Right now, I don't have any strong opinion, but I guess
that, while this driver is still at staging, it sounds good to be
able of using traces instead of dmesg for debugging purposes, but
to be honest, I didn't test yet to use ftrace for such purpose.

Thanks,
Mauro