checkpatch: warn when formats use %Z and suggest %z

vsnprintf extension %Z<foo> is non-standard C.  Suggest the use of %z
instead.

Miscellanea:

 - Correct the misuse of type string PRINTF_0xDECIMAL type strings are
   supposed to be uppercase only. Fix this and add tr/[a-z]/[A-Z] to the
   type check in case I forget this again sometime in the future.

 - Improve the mechanism to find these defects so all 3 current checks
   are done on the format string

[joe@perches.com: correct the misuse of type string PRINTF_0xDECIMAL, improve the mechanism to find these defects]
  Link: http://lkml.kernel.org/r/4e3ad74b0c9dc229b06018a2d79655308ddbbebd.1484014173.git.joe@perches.com
Link: http://lkml.kernel.org/r/20170109235955.GA6787@avx2
Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Signed-off-by: Joe Perches <joe@perches.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

scripts/checkpatch.pl

@@ -1848,6 +1848,8 @@ sub possible {
 sub show_type {
 	my ($type) = @_;
 
+	$type =~ tr/[a-z]/[A-Z]/;
+
 	return defined $use_type{$type} if (scalar keys %use_type > 0);
 
 	return !defined $ignore_type{$type};
@@ -5204,18 +5206,27 @@ sub process {
 			     "Consecutive strings are generally better as a single string\n" . $herecurr);
 		}
 
-# check for %L{u,d,i} and 0x%[udi] in strings
-		my $string;
+# check for non-standard and hex prefixed decimal printf formats
+		my $show_L = 1;	#don't show the same defect twice
+		my $show_Z = 1;
 		while ($line =~ /(?:^|")([X\t]*)(?:"|$)/g) {
-			$string = substr($rawline, $-[1], $+[1] - $-[1]);
+			my $string = substr($rawline, $-[1], $+[1] - $-[1]);
 			$string =~ s/%%/__/g;
-			if ($string =~ /(?<!%)%[\*\d\.\$]*L[udi]/) {
+			# check for %L
+			if ($show_L && $string =~ /%[\*\d\.\$]*L([diouxX])/) {
 				WARN("PRINTF_L",
-				     "\%Ld/%Lu are not-standard C, use %lld/%llu\n" . $herecurr);
-				last;
-			}
-			if ($string =~ /0x%[\*\d\.\$\Llzth]*[udi]/) {
-				ERROR("PRINTF_0xDECIMAL",
+				     "\%L$1 is non-standard C, use %ll$1\n" . $herecurr);
+				$show_L = 0;
+			}
+			# check for %Z
+			if ($show_Z && $string =~ /%[\*\d\.\$]*Z([diouxX])/) {
+				WARN("PRINTF_Z",
+				     "%Z$1 is non-standard C, use %z$1\n" . $herecurr);
+				$show_Z = 0;
+			}
+			# check for 0x<decimal>
+			if ($string =~ /0x%[\*\d\.\$\Llzth]*[diou]/) {
+				ERROR("PRINTF_0XDECIMAL",
 				      "Prefixing 0x with decimal output is defective\n" . $herecurr);
 			}
 		}