linux-kernel - [PATCH RFC] checkpatch: fix multi-statement macro checks

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Message-Id: <20201001103314.136645-1-dwaipayanray1@gmail.com>
Date:   Thu,  1 Oct 2020 16:03:14 +0530
From:   Dwaipayan Ray <dwaipayanray1@...il.com>
To:     joe@...ches.com
Cc:     linux-kernel@...r.kernel.org,
        linux-kernel-mentees@...ts.linuxfoundation.org,
        dwaipayanray1@...il.com, lukas.bulwahn@...il.com
Subject: [PATCH RFC] checkpatch: fix multi-statement macro checks

Checkpatch.pl doesn't have a check for excluding while (...) {...}
blocks from MULTISTATEMENT_MACRO_USE_DO_WHILE error.

For example, running checkpatch.pl on the file mm/access.c in the
kernel generates the following error:

ERROR: Macros with complex values should be enclosed in parentheses
+#define copy_from_kernel_nofault_loop(dst, src, len, type, err_label)	\
+	while (len >= sizeof(type)) {					\
+		__get_kernel_nofault(dst, src, type, err_label);	\
+		dst += sizeof(type);					\
+		src += sizeof(type);					\
+		len -= sizeof(type);					\
+	}

The error is misleading for this case. Enclosing it in parantheses
doesn't make any sense.

Checkpatch already has an exception list for such common macro types.
Added a new exception for while (...) {...} style blocks to the same.
This effectively fixed the wrong error message.

Signed-off-by: Dwaipayan Ray <dwaipayanray1@...il.com>
---
 scripts/checkpatch.pl | 1 +
 1 file changed, 1 insertion(+)

diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
index 72c4072307ea..c2c211374662 100755
--- a/scripts/checkpatch.pl
+++ b/scripts/checkpatch.pl
@@ -5342,6 +5342,7 @@ sub process {
 			    $dstat !~ /^\.$Ident\s*=/ &&				# .foo =
 			    $dstat !~ /^(?:\#\s*$Ident|\#\s*$Constant)\s*$/ &&		# stringification #foo
 			    $dstat !~ /^do\s*$Constant\s*while\s*$Constant;?$/ &&	# do {...} while (...); // do {...} while (...)
+			    $dstat !~ /^while\s*$Constant\s*$Constant\s*$/ &&		# while (...) {...}
 			    $dstat !~ /^for\s*$Constant$/ &&				# for (...)
 			    $dstat !~ /^for\s*$Constant\s+(?:$Ident|-?$Constant)$/ &&	# for (...) bar()
 			    $dstat !~ /^do\s*{/ &&					# do {...
-- 
2.27.0