Added and documented UNNECESSARY_ELSE message type.
Signed-off-by: Utkarsh Verma <utkarshverma294@xxxxxxxxx>
---
Documentation/dev-tools/checkpatch.rst | 77 ++++++++++++++++++++++++++
1 file changed, 77 insertions(+)
diff --git a/Documentation/dev-tools/checkpatch.rst b/Documentation/dev-tools/checkpatch.rst
index f0956e9ea2d8..e0f1ea1a0911 100644
--- a/Documentation/dev-tools/checkpatch.rst
+++ b/Documentation/dev-tools/checkpatch.rst
@@ -1166,3 +1166,80 @@ Others
**TYPO_SPELLING**
Some words may have been misspelled. Consider reviewing them.
+
+ **UNNECESSARY_ELSE**
+ Using an else statement just after a return or a break statement is
+ unnecessary. For example::
+
+ for (i = 0; i < 100; i++) {
+ int foo = bar();
+ if (foo < 1)
+ break;
+ else
+ usleep(1);
+ }
+
+ is generally better written as::
+
+ for (i = 0; i < 100; i++) {
+ int foo = bar();
+ if (foo < 1)
+ break;
+ usleep(1);
+ }
+
+ It helps to reduce the indentation and removes the unnecessary else
+ statement. But note there can be some false positives because of the
+ way it is implemented in the checkpatch script. The checkpatch script
+ throws this warning message if it finds an else statement and the line
+ above it is a break or return statement indented at one tab more than
+ the else statement. So there can be some false positives like::
+
+ int n = 15;
+ if (n > 10)
+ n--;
+ else if (n == 10)
+ return 0;
+ else
+ n++;
+
+ Now the checkpatch will give a warning for the use of else after return
+ statement. If the else statement is removed then::
+
+ int n = 15;
+ if (n > 10)
+ n--;
+ else if (n == 10)
+ return 0;
+ n++;
+
+ Now both the n-- and n++ statements will be executed which is different
+ from the logic in the first case. Because the if block doesn't have
+ a return statement, so removing the else statement is wrong.
+
+ Always check the previous if/else if blocks, for break/return
+ statements, and do not blindly follow the checkpatch advice. One
+ patch https://lore.kernel.org/all/20200615155131.GA4563@sevic69/
+ even made it to the mainline, which was again reverted and fixed.
+ Commit 98fe05e21a6e ("staging: rtl8712: Remove unnecesary else
+ after return statement.")
+
+ Also, do not change the code if there is only a single return/break
+ statement inside if-else block, like::
+
+ if (a > b)
+ return a;
+ else
+ return b;
+
+ now if the else statement is removed::
+
+ if (a > b)
+ return a;
+ return b;
+
+ there is no considerable increase in the readability and one can argue
+ that the first form is more readable because of the indentation. So
+ do not remove the else statement in case of a single return/break
+ statements inside the if-else block.
+ See: https://lore.kernel.org/lkml/20140925032215.GK7996@xxxxxxxxxxxxxxxxxx/
--
2.25.1
