[PATCH] checkpatch: Add a --strict test for macro argument reuse and precedence

[Joe Perches <joe@perches.com>]

Add a test for reuse of macro arguments to highlight any possible
side-effects from this reuse.

Avoid this check on token name pasting and when the
argument is used in a typeof or a __builtin.

Add a test for macro arguents that have leading or trailing operators
where the argument isn't parenthesized to avoid possible precedence
issues.

These tests are noisy so make them --strict.

Signed-off-by: Joe Perches <joe@perches.com>
---

This is a slight expansion of a patch I sent a few years back.

https://lkml.org/lkml/2012/11/6/151

This one at least runs.

Maybe it's useful to find some of the possible macro misuses,
but it is _very_ noisy.

 scripts/checkpatch.pl | 47 +++++++++++++++++++++++++++++++++++++++--------
 1 file changed, 39 insertions(+), 8 deletions(-)

diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
index 8946904..921155f 100755
--- a/scripts/checkpatch.pl
+++ b/scripts/checkpatch.pl
@@ -4714,7 +4714,17 @@ sub process {
 			$has_flow_statement = 1 if ($ctx =~ /\b(goto|return)\b/);
 			$has_arg_concat = 1 if ($ctx =~ /\#\#/ && $ctx !~ /\#\#\s*(?:__VA_ARGS__|args)\b/);
 
-			$dstat =~ s/^.\s*\#\s*define\s+$Ident(?:\([^\)]*\))?\s*//;
+			$dstat =~ s/^.\s*\#\s*define\s+$Ident(\([^\)]*\))?\s*//;
+			my $define_args = $1;
+			my $define_stmt = $dstat;
+			my @def_args = ();
+
+			if (defined $define_args && $define_args ne "") {
+				$define_args = substr($define_args, 1, length($define_args) - 2);
+				$define_args =~ s/\s*//g;
+				@def_args = split(",", $define_args);
+			}
+
 			$dstat =~ s/$;//g;
 			$dstat =~ s/\\\n.//g;
 			$dstat =~ s/^\s*//s;
@@ -4750,6 +4760,15 @@ sub process {
 				^\[
 			}x;
 			#print "REST<$rest> dstat<$dstat> ctx<$ctx>\n";
+
+			$ctx =~ s/\n*$//;
+			my $herectx = $here . "\n";
+			my $stmt_cnt = statement_rawlines($ctx);
+
+			for (my $n = 0; $n < $stmt_cnt; $n++) {
+				$herectx .= raw_line($linenr, $n) . "\n";
+			}
+
 			if ($dstat ne '' &&
 			    $dstat !~ /^(?:$Ident|-?$Constant),$/ &&			# 10, // foo(),
 			    $dstat !~ /^(?:$Ident|-?$Constant);$/ &&			# foo();
@@ -4765,13 +4784,6 @@ sub process {
 			    $dstat !~ /^\(\{/ &&						# ({...
 			    $ctx !~ /^.\s*#\s*define\s+TRACE_(?:SYSTEM|INCLUDE_FILE|INCLUDE_PATH)\b/)
 			{
-				$ctx =~ s/\n*$//;
-				my $herectx = $here . "\n";
-				my $cnt = statement_rawlines($ctx);
-
-				for (my $n = 0; $n < $cnt; $n++) {
-					$herectx .= raw_line($linenr, $n) . "\n";
-				}
 
 				if ($dstat =~ /;/) {
 					ERROR("MULTISTATEMENT_MACRO_USE_DO_WHILE",
@@ -4780,6 +4792,25 @@ sub process {
 					ERROR("COMPLEX_MACRO",
 					      "Macros with complex values should be enclosed in parentheses\n" . "$herectx");
 				}
+
+			}
+# check if any macro arguments are reused or may have other precedence issues
+			foreach my $arg (@def_args) {
+			        next if ($arg =~ /\.\.\./);
+				my $tmp = $define_stmt;
+				$tmp =~ s/\b(typeof|__typeof__|__builtin\w+|typecheck\s*\(\s*$Type\s*,|\#+)\s*\(*\s*$arg\s*\)*\b//g;
+				$tmp =~ s/\#\#\s*$arg\b//g;
+				$tmp =~ s/\b$arg\s*\#\#//g;
+				my $use_cnt = $tmp =~ s/\b$arg\b//g;
+				if ($use_cnt > 1) {
+					CHK("MACRO_ARG_REUSE",
+					    "Macro argument reuse '$arg' - possible side-effects?\n" . "$herectx");
+				}
+				if ($define_stmt =~ m/\b$arg\b\s*$Operators/m ||
+				    $define_stmt =~ /$Operators\s*$arg\b/m) {
+					CHK("MACRO_ARG_PRECEDENCE",
+					    "Macro argument '$arg' may be better as '($arg)' to avoid precedence issues\n" . "$herectx");
+				}
 			}
 
 # check for macros with flow control, but without ## concatenation
-- 
2.10.0.rc2.1.g053435c