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Subject[PATCH v2] checkpatch: Suggest using min_t or max_t
Date
A common issue with min() or max() is using a cast on
one or both of the arguments when using min_t/max_t could
be better.

Add cast detection to uses of min/max and suggest an
appropriate use of min_t or max_t instead.

Caveat: This only works for min() or max() on a single line.
It does not find min() or max() split across multiple lines.

This does find:
min((u32)foo, bar);
But it does not find:
max((unsigned long)foo,
bar);

Suggested-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Joe Perches <joe@perches.com>
---

v2: Make $match_balanced_parentheses work in perl 5.8

scripts/checkpatch.pl | 35 +++++++++++++++++++++++++++++++++++
1 files changed, 35 insertions(+), 0 deletions(-)

diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
index 8657f99..897aff8 100755
--- a/scripts/checkpatch.pl
+++ b/scripts/checkpatch.pl
@@ -268,6 +268,20 @@ sub build_types {
}
build_types();

+our $match_balanced_parentheses = qr/(\((?:[^\(\)]+|(-1))*\))/;
+
+our $Typecast = qr{\s*(\(\s*$NonptrType\s*\)){0,1}\s*};
+our $LvalOrFunc = qr{($Lval)\s*($match_balanced_parentheses{0,1})\s*};
+
+sub deparenthesize {
+ my ($string) = @_;
+ return "" if (!defined($string));
+ $string =~ s@^\s*\(\s*@@g;
+ $string =~ s@\s*\)\s*$@@g;
+ $string =~ s@\s+@ @g;
+ return $string;
+}
+
$chk_signoff = 0 if ($file);

my @dep_includes = ();
@@ -2285,6 +2299,27 @@ sub process {
}
}

+# typecasts on min/max could be min_t/max_t
+ if ($line =~ /^\+(?:.*?)\b(min|max)\s*\($Typecast{0,1}($LvalOrFunc)\s*,\s*$Typecast{0,1}($LvalOrFunc)\s*\)/) {
+ if (defined $2 || defined $8) {
+ my $call = $1;
+ my $cast1 = deparenthesize($2);
+ my $arg1 = $3;
+ my $cast2 = deparenthesize($8);
+ my $arg2 = $9;
+ my $cast;
+
+ if ($cast1 ne "" && $cast2 ne "") {
+ $cast = "$cast1 or $cast2";
+ } elsif ($cast1 ne "") {
+ $cast = $cast1;
+ } else {
+ $cast = $cast2;
+ }
+ WARN("$call() should probably be ${call}_t($cast, $arg1, $arg2)\n" . $herecurr);
+ }
+ }
+
# Need a space before open parenthesis after if, while etc
if ($line=~/\b(if|while|for|switch)\(/) {
ERROR("space required before the open parenthesis '('\n" . $herecurr);
--
1.7.5.2.365.g5cfe4

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