docs: scripts/kernel-doc: Detect absence of FILE arg

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: Randy Dunlap <rdunlap@infradead.org>
Link: https://lore.kernel.org/r/7b136049-a3ba-0eb5-8717-364d773ff914@gmail.com
[jc: reworked to fix conflict with pod patches]
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

diff --git a/scripts/kernel-doc b/scripts/kernel-doc
index f06f68f..9c084a2 100755 (executable)
--- a/scripts/kernel-doc
+++ b/scripts/kernel-doc
@@ -343,14 +343,23 @@ while ($ARGV[0] =~ m/^--?(.*)/) {
            die "Sphinx version should either major.minor or major.minor.patch format\n";
        }
     } else {
-               # Unknown argument
-               pod2usage(
-                       -message => "Argument unknown!\n",
-                       -exitval => 1,
-                       -verbose => 99,
-                       -sections => 'SYNOPSIS',
-                       -output => \*STDERR,
-               );
+       # Unknown argument
+       pod2usage(
+           -message => "Argument unknown!\n",
+           -exitval => 1,
+           -verbose => 99,
+           -sections => 'SYNOPSIS',
+           -output => \*STDERR,
+           );
+    }
+    if ($#ARGV < 0){
+       pod2usage(
+           -message => "FILE argument missing\n",
+           -exitval => 1,
+           -verbose => 99,
+           -sections => 'SYNOPSIS',
+           -output => \*STDERR,
+           );
     }
 }