checkpatch: warn when using extern with function prototypes in .h files

Using the extern keyword on function prototypes is superfluous visual
noise so suggest removing it.

Using extern can cause unnecessary line wrapping at 80 columns and
unnecessarily long multi-line function prototypes.

Signed-off-by: Joe Perches <joe@perches.com>
Suggested-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 10 insertions, 0 deletions

diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
index 7c79c91662c8..e2cb1f4621b7 100755
--- a/scripts/checkpatch.pl
+++ b/scripts/checkpatch.pl
@@ -3878,6 +3878,16 @@ sub process {
                         }
                 }
 
+# check for new externs in .h files.
+                if ($realfile =~ /\.h$/ &&
+                    $line =~ /^\+\s*(extern\s+)$Type\s*$Ident\s*\(/s) {
+                        if (WARN("AVOID_EXTERNS",
+                                 "extern prototypes should be avoided in .h files\n" . $herecurr) &&
+                            $fix) {
+                                $fixed[$linenr - 1] =~ s/(.*)\bextern\b\s*(.*)/$1$2/;
+                        }
+                }
+
 # check for new externs in .c files.
                 if ($realfile =~ /\.c$/ && defined $stat &&
                     $stat =~ /^.\s*(?:extern\s+)?$Type\s+($Ident)(\s*)\(/s)