[PATCH v2] docs: scripts/kernel-doc: Detect absence of FILE arg

[Akira Yokosawa <akiyks@gmail.com>]

Currently, when there is no FILE argument following a switch such
as -man, -rst, or -none, kernel-doc exits with a warning from perl
(long msg folded):

    Use of uninitialized value $ARGV[0] in pattern match (m//)
    at ./scripts/kernel-doc line 438.

, which is unhelpful.

Improve the behavior by adding a check at the bottom of parsing
loop.
If the argument is absent, display help text and exit with
the code of 1 (via usage()).

Signed-off-by: Akira Yokosawa <akiyks@gmail.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Tomasz Warniełło <tomasz.warniello@gmail.com>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: linux-doc@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
---
Changes since v1 [1]:
  - No code change
  - Amend subject and reword the whole changelog.
  - The message from perl is not an error but a warning.
     (I thank Tomasz for pointing it out.)

I thought the change of exit code might affect sphinx-build processing,
and tested with several runs of "make htmldocs" and "make pdfdocs".
So far, I've not seen any regression.

[1] v1: https://lore.kernel.org/r/1c71e5d2-f87e-6c8e-6176-e5ce42e4d41b@gmail.com

        Thanks, Akira
--
 scripts/kernel-doc | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/scripts/kernel-doc b/scripts/kernel-doc
index 3106b7536b89..faefe2977f0e 100755
--- a/scripts/kernel-doc
+++ b/scripts/kernel-doc
@@ -494,7 +494,11 @@ while ($ARGV[0] =~ m/^--?(.*)/) {
 	}
     } else {
 	# Unknown argument
-        usage();
+	usage();
+    }
+    if ($#ARGV < 0){
+	print "No FILE!\n";
+	usage();
     }
 }
 

base-commit: b62ef3a1cca0553613adce16515f3640400725b4
-- 
2.17.1