On Wed, 2024-07-24 at 22:09 -0400, Julian Sun wrote:

Joe Perches [off-list ref] 于2024年7月24日周三 09:30写道：

quoted

On Tue, 2024-07-23 at 05:11 -0400, Julian Sun wrote:

quoted

Hi,

Recently, I saw a patch[1] on the ext4 mailing list regarding
the correction of a macro definition error. Jan mentioned
that "The bug in the macro is a really nasty trap...".
Because existing compilers are unable to detect
unused parameters in macro definitions. This inspired me
to write a script to check for unused parameters in
macro definitions and to run it.

checkpatch has a similar test:

https://lkml.kernel.org/r/20240507032757.146386-3-21cnbao@gmail.com

$ git log --format=email -1 b1be5844c1a0124a49a30a20a189d0a53aa10578
From b1be5844c1a0124a49a30a20a189d0a53aa10578 Mon Sep 17 00:00:00 2001
From: Xining Xu <redacted>
Date: Tue, 7 May 2024 15:27:57 +1200
Subject: [PATCH] scripts: checkpatch: check unused parameters for
 function-like macro

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.

 WARNING: Argument 'a' is not used in function-like macro
 #21: FILE: mm/init-mm.c:20:
 +#define test(a) do { } while (0)

 total: 0 errors, 1 warnings, 8 lines checked

quoted

Link: https://lkml.kernel.org/r/20240507032757.146386-3-21cnbao@gmail.com

Yeah, I noticted the test. The difference between checkpatch and
macro_checker is that checkpatch only checks the patch files, instead
of the entire source files, which results in the inability to check
all macros in source files.

Another possibility:

$ git ls-files -- '*.[ch]' | \
  xargs ./scripts/checkpatch -f --terse --no-summary --types=MACRO_ARG_UNUSED

Though I agree the addition of a test for "do {} while (0)" and
no content would be also be useful for unused macro args tests.
---
 scripts/checkpatch.pl | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
index 39032224d504f..285d29b3e9010 100755
--- a/scripts/checkpatch.pl
+++ b/scripts/checkpatch.pl

@@ -6060,7 +6060,9 @@ sub process {
 				}
 
 # check if this is an unused argument
-				if ($define_stmt !~ /\b$arg\b/) {
+				if ($define_stmt !~ /\b$arg\b/ &&
+				    $define_stmt !~ /^$/ &&
+				    $define_stmt !~ /^do\s*\{\s*\}\s*while\s*\(\s*0\s*\)$/) {
 					WARN("MACRO_ARG_UNUSED",
 					     "Argument '$arg' is not used in function-like macro\n" . "$herectx");
 				}