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From: Barry Song <21cnbao@gmail.com>
To: corbet@lwn.net,
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Cc: linux-kernel@vger.kernel.org,
	Xining Xu <ma.xxn@outlook.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Chris Zankel <chris@zankel.net>,
	Huacai Chen <chenhuacai@loongson.cn>,
	Herbert Xu <herbert@gondor.apana.org.au>,
	Guenter Roeck <linux@roeck-us.net>,
	Stephen Rothwell <sfr@canb.auug.org.au>,
	Mark Brown <broonie@kernel.org>,
	Barry Song <v-songbaohua@oppo.com>
Subject: [PATCH v3 2/2] scripts: checkpatch: Check unused parameters for function-like macro
Date: Fri, 22 Mar 2024 21:49:37 +1300
Message-Id: <20240322084937.66018-3-21cnbao@gmail.com>
In-Reply-To: <20240322084937.66018-1-21cnbao@gmail.com>
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From: Xining Xu <ma.xxn@outlook.com>

If function-like macros do not utilize a parameter, it might result in a
build warning. In our coding style guidelines, we advocate for utilizing
static inline functions to replace such macros. This patch verifies
compliance with the new rule.

For a macro such as the one below,

 #define test(a) do { } while (0)

The test result is as follows.

 ERROR: Parameter 'a' is not used in function-like macro, please use static
 inline instead
 #21: FILE: mm/init-mm.c:20:
 +#define test(a) do { } while (0)

 total: 1 errors, 0 warnings, 8 lines checked

Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Chris Zankel <chris@zankel.net>
Cc: Huacai Chen <chenhuacai@loongson.cn>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Cc: Guenter Roeck <linux@roeck-us.net>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Cc: Mark Brown <broonie@kernel.org>
Signed-off-by: Xining Xu <ma.xxn@outlook.com>
Tested-by: Barry Song <v-songbaohua@oppo.com>
---
 scripts/checkpatch.pl | 24 ++++++++++++++++++++++++
 1 file changed, 24 insertions(+)

diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
index 9c4c4a61bc83..6f778f3403b5 100755
--- a/scripts/checkpatch.pl
+++ b/scripts/checkpatch.pl
@@ -6109,6 +6109,30 @@ sub process {
 				WARN("TRAILING_SEMICOLON",
 				     "macros should not use a trailing semicolon\n" . "$herectx");
 			}
+
+			if ($dstat =~ /^\+\s*#\s*define\s+$Ident\s*(\((?:[^\(\)]++|(?-1))*\))\s+(\S+.*)(\/\/.*)?/) {
+				my $params = $1 || "";
+				my $body = $2 || "";
+
+			    # get the individual params
+				$params =~ tr/()//d;
+				# remove leading and trailing whitespace
+				$params =~ s/^\s+|\s+$//g;
+
+				$ctx =~ s/\n*$//;
+				my $cnt = statement_rawlines($ctx);
+				my $herectx = get_stat_here($linenr, $cnt, $here);
+
+				if ($params ne "") {
+					my @paramList = split /,\s*/, $params;
+					foreach my $param(@paramList) {
+						if ($body !~ /\b$param\b/) {
+							ERROR("UNUSED_PARAM_IN_MACRO",
+							     "Parameter '$param' is not used in function-like macro, please use static inline instead\n" . "$herectx");
+						}
+					}
+				}
+			}
 		}
 
 # check for redundant bracing round if etc
-- 
2.34.1