checkpatch: improve blank line after declaration test

Avoid multiple false positives by ignoring attributes.

Various attributes like volatile and ____cacheline_aligned_in_smp cause
checkpatch to emit invalid "Missing a blank line after declarations"
messages.

Use copies of $sline and $prevline, remove $Attribute and $Sparse, and use
the existing tests to avoid these false positives.

Miscellanea:

o Add volatile to $Attribute

This also reduces checkpatch runtime a bit by moving the indentation
comparison test to the start of the block to avoid multiple unnecessary
regex tests.

Link: https://lkml.kernel.org/r/9015fd00742bf4e5b824ad6d7fd7189530958548.camel@perches.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

@@ -382,6 +382,7 @@ sub hash_show_words {
 # We need \b after 'init' otherwise 'initconst' will cause a false positive in a check
 our $Attribute	= qr{
 			const|
+			volatile|
 			__percpu|
 			__nocast|
 			__safe|
@@ -3776,43 +3777,48 @@ sub process {
 		}
 
 # check for missing blank lines after declarations
-		if ($sline =~ /^\+\s+\S/ &&			#Not at char 1
-			# actual declarations
-		    ($prevline =~ /^\+\s+$Declare\s*$Ident\s*[=,;:\[]/ ||
+# (declarations must have the same indentation and not be at the start of line)
+		if (($prevline =~ /\+(\s+)\S/) && $sline =~ /^\+$1\S/) {
+			# use temporaries
+			my $sl = $sline;
+			my $pl = $prevline;
+			# remove $Attribute/$Sparse uses to simplify comparisons
+			$sl =~ s/\b(?:$Attribute|$Sparse)\b//g;
+			$pl =~ s/\b(?:$Attribute|$Sparse)\b//g;
+			if (($pl =~ /^\+\s+$Declare\s*$Ident\s*[=,;:\[]/ ||
 			# function pointer declarations
-		     $prevline =~ /^\+\s+$Declare\s*\(\s*\*\s*$Ident\s*\)\s*[=,;:\[\(]/ ||
+			     $pl =~ /^\+\s+$Declare\s*\(\s*\*\s*$Ident\s*\)\s*[=,;:\[\(]/ ||
 			# foo bar; where foo is some local typedef or #define
-		     $prevline =~ /^\+\s+$Ident(?:\s+|\s*\*\s*)$Ident\s*[=,;\[]/ ||
+			     $pl =~ /^\+\s+$Ident(?:\s+|\s*\*\s*)$Ident\s*[=,;\[]/ ||
 			# known declaration macros
-		     $prevline =~ /^\+\s+$declaration_macros/) &&
+			     $pl =~ /^\+\s+$declaration_macros/) &&
 			# for "else if" which can look like "$Ident $Ident"
-		    !($prevline =~ /^\+\s+$c90_Keywords\b/ ||
+			    !($pl =~ /^\+\s+$c90_Keywords\b/ ||
 			# other possible extensions of declaration lines
-		      $prevline =~ /(?:$Compare|$Assignment|$Operators)\s*$/ ||
+			      $pl =~ /(?:$Compare|$Assignment|$Operators)\s*$/ ||
 			# not starting a section or a macro "\" extended line
-		      $prevline =~ /(?:\{\s*|\\)$/) &&
+			      $pl =~ /(?:\{\s*|\\)$/) &&
 			# looks like a declaration
-		    !($sline =~ /^\+\s+$Declare\s*$Ident\s*[=,;:\[]/ ||
+			    !($sl =~ /^\+\s+$Declare\s*$Ident\s*[=,;:\[]/ ||
 			# function pointer declarations
-		      $sline =~ /^\+\s+$Declare\s*\(\s*\*\s*$Ident\s*\)\s*[=,;:\[\(]/ ||
+			      $sl =~ /^\+\s+$Declare\s*\(\s*\*\s*$Ident\s*\)\s*[=,;:\[\(]/ ||
 			# foo bar; where foo is some local typedef or #define
-		      $sline =~ /^\+\s+$Ident(?:\s+|\s*\*\s*)$Ident\s*[=,;\[]/ ||
+			      $sl =~ /^\+\s+$Ident(?:\s+|\s*\*\s*)$Ident\s*[=,;\[]/ ||
 			# known declaration macros
-		      $sline =~ /^\+\s+$declaration_macros/ ||
+			      $sl =~ /^\+\s+$declaration_macros/ ||
 			# start of struct or union or enum
-		      $sline =~ /^\+\s+(?:static\s+)?(?:const\s+)?(?:union|struct|enum|typedef)\b/ ||
+			      $sl =~ /^\+\s+(?:static\s+)?(?:const\s+)?(?:union|struct|enum|typedef)\b/ ||
 			# start or end of block or continuation of declaration
-		      $sline =~ /^\+\s+(?:$|[\{\}\.\#\"\?\:\(\[])/ ||
+			      $sl =~ /^\+\s+(?:$|[\{\}\.\#\"\?\:\(\[])/ ||
 			# bitfield continuation
-		      $sline =~ /^\+\s+$Ident\s*:\s*\d+\s*[,;]/ ||
+			      $sl =~ /^\+\s+$Ident\s*:\s*\d+\s*[,;]/ ||
 			# other possible extensions of declaration lines
-		      $sline =~ /^\+\s+\(?\s*(?:$Compare|$Assignment|$Operators)/) &&
-			# indentation of previous and current line are the same
-		    (($prevline =~ /\+(\s+)\S/) && $sline =~ /^\+$1\S/)) {
-			if (WARN("LINE_SPACING",
-				 "Missing a blank line after declarations\n" . $hereprev) &&
-			    $fix) {
-				fix_insert_line($fixlinenr, "\+");
+			      $sl =~ /^\+\s+\(?\s*(?:$Compare|$Assignment|$Operators)/)) {
+				if (WARN("LINE_SPACING",
+					 "Missing a blank line after declarations\n" . $hereprev) &&
+				    $fix) {
+					fix_insert_line($fixlinenr, "\+");
+				}
 			}
 		}