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Subject[RFC PATCH 1/1] checkpatch: don't suggest else is not useful with chained
When if blocks are chained with "else if" like this:

if (a)
c = 0;
else if (b)
break;
else
c = 1;

checkpatch recommends removing else:

WARNING: else is not generally useful after a break or return

Removing else will easily introduce logic errors in this situation
so it's better to check if the preceding line has "else if" before
issuing that warning.

Fixes: 032a4c0f9a77 ("checkpatch: warn on unnecessary else after return or break")
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
---

I was only able to solve this case for single line if blocks but
it would be useful to address also multi-line if blocks but it is
beyond my understanding about checkpatch internals.

scripts/checkpatch.pl | 13 ++++++++-----
1 file changed, 8 insertions(+), 5 deletions(-)

diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
index b01c36a15d9d..8e095b77bfb6 100755
--- a/scripts/checkpatch.pl
+++ b/scripts/checkpatch.pl
@@ -4037,14 +4037,17 @@ sub process {
# check indentation of any line with a bare else
# (but not if it is a multiple line "if (foo) return bar; else return baz;")
# if the previous line is a break or return and is indented 1 tab more...
+# but don't warn when there is "else if" on before that line to avoid logic errors
if ($sline =~ /^\+([\t]+)(?:}[ \t]*)?else(?:[ \t]*{)?\s*$/) {
my $tabs = length($1) + 1;
- if ($prevline =~ /^\+\t{$tabs,$tabs}break\b/ ||
- ($prevline =~ /^\+\t{$tabs,$tabs}return\b/ &&
- defined $lines[$linenr] &&
- $lines[$linenr] !~ /^[ \+]\t{$tabs,$tabs}return/)) {
+ if ($linenr >= 3 &&
+ $lines[$linenr - 3] !~ /[} \t]else\s+if\s*\(/ &&
+ ($prevline =~ /^\+\t{$tabs,$tabs}break\b/ ||
+ ($prevline =~ /^\+\t{$tabs,$tabs}return\b/ &&
+ defined $lines[$linenr] &&
+ $lines[$linenr] !~ /^[ \+]\t{$tabs,$tabs}return/))) {
WARN("UNNECESSARY_ELSE",
- "else is not generally useful after a break or return\n" . $hereprev);
+ "else is not generally useful after a break or return\n" . $hereprev . "\n");
}
}

--
2.30.2
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