Hi Petr,

I love your patch! Yet something to improve:

[auto build test ERROR on next-20180424]
[cannot apply to linus/master v4.17-rc2 v4.17-rc1 v4.16 v4.17-rc2]
[if your patch is applied to the wrong git tree, please drop us a note to help improve the system]

url:    https://github.com/0day-ci/linux/commits/Petr-Mladek/vsprintf-Prevent-silent-crashes-and-consolidate-error-handling/20180427-044114
config: i386-randconfig-x000-201816 (attached as .config)
compiler: gcc-7 (Debian 7.3.0-16) 7.3.0
reproduce:
        # save the attached .config to linux build tree
        make ARCH=i386 

All errors (new ones prefixed by >>):

   lib/test_printf.c: In function 'plain':
>> lib/test_printf.c:271:8: error: too many arguments to function 'plain_format'
     err = plain_format(ptr);
           ^~~~~~~~~~~~
   lib/test_printf.c:233:1: note: declared here
    plain_format(void)
    ^~~~~~~~~~~~

vim +/plain_format +271 lib/test_printf.c

   254	
   255	/*
   256	 * We can't use test() to test %p because we don't know what output to expect
   257	 * after an address is hashed.
   258	 */
   259	static void __init
   260	plain(void *ptr)
   261	{
   262		int err;
   263	
   264		err = plain_hash(ptr);
   265		if (err) {
   266			pr_warn("plain 'p' does not appear to be hashed\n");
   267			failed_tests++;
   268			return;
   269		}
   270	
 > 271		err = plain_format(ptr);
   272		if (err) {
   273			pr_warn("hashing plain 'p' has unexpected format\n");
   274			failed_tests++;
   275		}
   276	}
   277	

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