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authorUtkarsh Verma <utkarshverma294@gmail.com>2021-09-25 19:38:52 +0300
committerJonathan Corbet <corbet@lwn.net>2021-09-27 20:42:45 +0300
commit250a0a5ba9d2cfbdb7c77b421ff1e03d630bea46 (patch)
treeb192b2144ab9977186d4544935c1d22bec91b834 /Documentation/dev-tools/checkpatch.rst
parentcbb817fc2effcbee0eb44303eefbc8171fc2b12f (diff)
downloadlinux-250a0a5ba9d2cfbdb7c77b421ff1e03d630bea46.tar.xz
docs: checkpatch: add multiline, do/while, and multiple-assignment messages
Added and documented 3 new message types: - MULTILINE_DEREFERENCE - SINGLE_STATEMENT_DO_WHILE_MACRO - MULTIPLE_ASSIGNMENTS Signed-off-by: Utkarsh Verma <utkarshverma294@gmail.com> Link: https://lore.kernel.org/r/20210925163852.12096-1-utkarshverma294@gmail.com Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Diffstat (limited to 'Documentation/dev-tools/checkpatch.rst')
-rw-r--r--Documentation/dev-tools/checkpatch.rst43
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diff --git a/Documentation/dev-tools/checkpatch.rst b/Documentation/dev-tools/checkpatch.rst
index 4f89c363db08..5cbc8463b1f0 100644
--- a/Documentation/dev-tools/checkpatch.rst
+++ b/Documentation/dev-tools/checkpatch.rst
@@ -716,6 +716,33 @@ Indentation and Line Breaks
See: https://lore.kernel.org/lkml/20120203052727.GA15035@leaf/
+ **MULTILINE_DEREFERENCE**
+ A single dereferencing identifier spanned on multiple lines like::
+
+ struct_identifier->member[index].
+ member = <foo>;
+
+ is generally hard to follow. It can easily lead to typos and so makes
+ the code vulnerable to bugs.
+
+ If fixing the multiple line dereferencing leads to an 80 column
+ violation, then either rewrite the code in a more simple way or if the
+ starting part of the dereferencing identifier is the same and used at
+ multiple places then store it in a temporary variable, and use that
+ temporary variable only at all the places. For example, if there are
+ two dereferencing identifiers::
+
+ member1->member2->member3.foo1;
+ member1->member2->member3.foo2;
+
+ then store the member1->member2->member3 part in a temporary variable.
+ It not only helps to avoid the 80 column violation but also reduces
+ the program size by removing the unnecessary dereferences.
+
+ But if none of the above methods work then ignore the 80 column
+ violation because it is much easier to read a dereferencing identifier
+ on a single line.
+
**TRAILING_STATEMENTS**
Trailing statements (for example after any conditional) should be
on the next line.
@@ -872,6 +899,17 @@ Macros, Attributes and Symbols
See: https://lore.kernel.org/lkml/1399671106.2912.21.camel@joe-AO725/
+ **SINGLE_STATEMENT_DO_WHILE_MACRO**
+ For the multi-statement macros, it is necessary to use the do-while
+ loop to avoid unpredictable code paths. The do-while loop helps to
+ group the multiple statements into a single one so that a
+ function-like macro can be used as a function only.
+
+ But for the single statement macros, it is unnecessary to use the
+ do-while loop. Although the code is syntactically correct but using
+ the do-while loop is redundant. So remove the do-while loop for single
+ statement macros.
+
**WEAK_DECLARATION**
Using weak declarations like __attribute__((weak)) or __weak
can have unintended link defects. Avoid using them.
@@ -947,6 +985,11 @@ Functions and Variables
Your compiler (or rather your loader) automatically does
it for you.
+ **MULTIPLE_ASSIGNMENTS**
+ Multiple assignments on a single line makes the code unnecessarily
+ complicated. So on a single line assign value to a single variable
+ only, this makes the code more readable and helps avoid typos.
+
**RETURN_PARENTHESES**
return is not a function and as such doesn't need parentheses::