[PATCH v2] Documentation: checkpatch: Add TRAILING_SEMICOLON message

Utkarsh Verma utkarshverma294 at gmail.com
Tue Aug 3 21:19:41 UTC 2021

Add a new message type TRAILING_SEMICOLON for the macro definitions
that conclude with a semicolon.

Suggested-by: Lukas Bulwahn <lukas.bulwahn at gmail.com>
Signed-off-by: Utkarsh Verma <utkarshverma294 at gmail.com>
 Documentation/dev-tools/checkpatch.rst | 21 +++++++++++++++++++++
 1 file changed, 21 insertions(+)

diff --git a/Documentation/dev-tools/checkpatch.rst b/Documentation/dev-tools/checkpatch.rst
index f0956e9ea..f2ef998ba 100644
--- a/Documentation/dev-tools/checkpatch.rst
+++ b/Documentation/dev-tools/checkpatch.rst
@@ -845,6 +845,27 @@ Macros, Attributes and Symbols
     Use the `fallthrough;` pseudo keyword instead of
     `/* fallthrough */` like comments.
+    Macro definition should not conclude with a semicolon. The macro
+    invocation should be consistent with the function call. So the macro
+    invocation must conclude with a semicolon. Suppose if a macro MAC is
+    defined::
+      #define MAC do_something;
+    If this macro is used within a if else statement, like::
+      if (some_condition)
+              MAC;
+      else
+              do_something;
+    Then there would be a compilation error, because when the macro is
+    expanded there are two trailing semicolons, so the else branch gets
+    orphaned.
+    See: https://lore.kernel.org/lkml/1399671106.2912.21.camel@joe-AO725/
     Using weak declarations like __attribute__((weak)) or __weak
     can have unintended link defects.  Avoid using them.

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