Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > linux.kernel > #1214740

[PATCH] checkpatch: add constant comparison on left side test

Show all headers | View raw

"CONST <comparison> variable" checks like:

        if (NULL != foo)
and
        while (0 < bar(...))

where a constant (or what appears to be a constant
like an upper case identifier) is on the left of a
comparison are generally preferred to be written
using the constant on the right side like:

        if (foo != NULL)
and
        while (bar(...) > 0)

Add a test for this.

Add a --fix option too, but only do it when the code
is immediately surrounded by parentheses to avoid
misfixing things like "(0 < bar() + constant)"

Signed-off-by: Joe Perches <joe@perches.com>
---
 scripts/checkpatch.pl | 29 +++++++++++++++++++++++++++++
 1 file changed, 29 insertions(+)

diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
index e14dcdb..5fca1da 100755
--- a/scripts/checkpatch.pl
+++ b/scripts/checkpatch.pl
@@ -4231,6 +4231,35 @@ sub process {
 			}
 		}
 
+# comparisons with a constant or upper case identifier on the left
+#	avoid cases like "foo + BAR < baz"
+#	only fix matches surrounded by parentheses to avoid incorrect
+#	conversions like "FOO < baz() + 5" being "misfixed" to "baz() > FOO + 5"
+		if ($^V && $^V ge 5.10.0 &&
+		    $line =~ /^\+(.*)\b($Constant|[A-Z_][A-Z0-9_]*)\s*($Compare)\s*($LvalOrFunc)/) {
+			my $lead = $1;
+			my $const = $2;
+			my $comp = $3;
+			my $to = $4;
+			my $newcomp = $comp;
+			if ($lead !~ /$Operators\s*$/ &&
+			    $to !~ /^(?:Constant|[A-Z_][A-Z0-9_]*)$/ &&
+			    WARN("CONSTANT_COMPARISON",
+				 "Comparisons should place the constant on the right side of the test\n" . $herecurr) &&
+			    $fix) {
+				if ($comp eq "<") {
+					$newcomp = ">";
+				} elsif ($comp eq "<=") {
+					$newcomp = ">=";
+				} elsif ($comp eq ">") {
+					$newcomp = "<";
+				} elsif ($comp eq ">=") {
+					$newcomp = "<=";
+				}
+				$fixed[$fixlinenr] =~ s/\(\s*\Q$const\E\s*$Compare\s*\Q$to\E\s*\)/($to $newcomp $const)/;
+			}
+		}
+
 # Return of what appears to be an errno should normally be negative
 		if ($sline =~ /\breturn(?:\s*\(+\s*|\s+)(E[A-Z]+)(?:\s*\)+\s*|\s*)[;:,]/) {
 			my $name = $1;


--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/

Back to linux.kernel | Previous | Next — Previous in thread | Find similar | Unroll thread

Thread

Re: [PATCH] checkpatch: add --strict "pointer comparison to NULL" test Viresh Kumar <viresh.kumar@linaro.org> - 2015-08-27 04:20 +0200
  Re: [PATCH] checkpatch: add --strict "pointer comparison to NULL"  test Joe Perches <joe@perches.com> - 2015-08-27 05:10 +0200
    Re: [PATCH] checkpatch: add --strict "pointer comparison to NULL"  test Nicolas Morey Chaisemartin <nmorey@kalray.eu> - 2015-08-27 09:20 +0200
      Re: [PATCH] checkpatch: add --strict "pointer comparison to NULL"  test Joe Perches <joe@perches.com> - 2015-08-27 09:30 +0200
        [PATCH] checkpatch: add constant comparison on left side test Joe Perches <joe@perches.com> - 2015-08-27 19:40 +0200

csiph-web