Re: [linux-stable-rc:linux-4.4.y 9981/9999] include/linux/printk.h:113:2: note: in expansion of macro 'if'

[Aaron Conole <aconole@redhat.com>]

kernel test robot <lkp@intel.com> writes:

> tree:   https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable-rc.git linux-4.4.y
> head:   bb07acdd9271518022b632253e857f43c09fb147
> commit: b60b53d4980f879884740e672d83155980d74445 [9981/9999] printk: help pr_debug and pr_devel to optimize out arguments
> config: i386-randconfig-s001-20200605 (attached as .config)
> compiler: gcc-7 (Ubuntu 7.5.0-6ubuntu2) 7.5.0
> reproduce:
>         # apt-get install sparse
>         # sparse version: v0.6.1-246-g41f651b4-dirty
>         git checkout b60b53d4980f879884740e672d83155980d74445
>         # save the attached .config to linux build tree
>         make W=1 C=1 ARCH=i386 CF='-fdiagnostic-prefix -D__CHECK_ENDIAN__'
>
> If you fix the issue, kindly add following tag as appropriate
> Reported-by: kernel test robot <lkp@intel.com>
>
> All warnings (new ones prefixed by >>, old ones prefixed by <<):
>
> In file included from include/linux/ioport.h:12:0,
> from include/linux/device.h:16,
> from include/linux/platform_device.h:14,
> from arch/x86/kernel/cpu/microcode/core.c:24:
> arch/x86/kernel/cpu/microcode/core.c: In function 'mc_cpu_callback':
> include/linux/compiler.h:163:5: warning: this statement may fall through [-Wimplicit-fallthrough=]
> if (__builtin_constant_p(!!(cond)) ? !!(cond) :           ^
> include/linux/compiler.h:161:23: note: in expansion of macro '__trace_if'
> #define if(cond, ...) __trace_if( (cond , ## __VA_ARGS__) )
> ^~~~~~~~~~
>>> include/linux/printk.h:113:2: note: in expansion of macro 'if'
> if (0)          ^~
> include/linux/printk.h:289:2: note: in expansion of macro 'no_printk'
> no_printk(KERN_DEBUG pr_fmt(fmt), ##__VA_ARGS__)
> ^~~~~~~~~
> arch/x86/kernel/cpu/microcode/core.c:599:3: note: in expansion of macro 'pr_debug'
> pr_debug("CPU%d addedn", cpu);
> ^~~~~~~~
> arch/x86/kernel/cpu/microcode/core.c:605:2: note: here
> case CPU_DOWN_FAILED:
> ^~~~

I guess there's a missing /* fallthrough */ tag for this case -
not sure why it flagged on this particular commit.

Doesn't look related.

> vim +/if +113 include/linux/printk.h
>
>    106	
>    107	/*
>    108	 * Dummy printk for disabled debugging statements to use whilst maintaining
>    109	 * gcc's format checking.
>    110	 */
>    111	#define no_printk(fmt, ...)			\
>    112	do {						\
>  > 113		if (0)					\
>    114			printk(fmt, ##__VA_ARGS__);	\
>    115	} while (0)
>    116	
>
> ---
> 0-DAY CI Kernel Test Service, Intel Corporation
> https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org