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

[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.

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

There are times when using a temporary for macro arguments
is overkill.  This patch might be overkill too.

 scripts/checkpatch.pl |   42 ++++++++++++++++++++++++++++++++++--------
 1 files changed, 34 insertions(+), 8 deletions(-)

diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
index d4f61a6..58fff6e 100755
--- a/scripts/checkpatch.pl
+++ b/scripts/checkpatch.pl
@@ -2952,7 +2952,17 @@ sub process {
 			#print "dstat<$dstat> dcond<$dcond> cnt<$cnt> off<$off>\n";
 			#print "LINE<$lines[$ln-1]> len<" . length($lines[$ln-1]) . "\n";
 
-			$dstat =~ s/^.\s*\#\s*define\s+$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;
 			$dstat =~ s/^\s*//s;
@@ -2984,6 +2994,15 @@ sub process {
 				^\"|\"$
 			}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();
@@ -2997,13 +3016,6 @@ sub process {
 			    $dstat !~ /^do\s*{/ &&					# do {...
 			    $dstat !~ /^\({/)						# ({...
 			{
-				$ctx =~ s/\n*$//;
-				my $herectx = $here . "\n";
-				my $cnt = statement_rawlines($ctx);
-
-				for (my $n = 0; $n < $cnt; $n++) {
-					$herectx .= raw_line($linenr, $n) . "\n";
-				}
 
 				if ($dstat =~ /;/) {
 					ERROR("MULTISTATEMENT_MACRO_USE_DO_WHILE",
@@ -3012,6 +3024,20 @@ sub process {
 					ERROR("COMPLEX_MACRO",
 					      "Macros with complex values should be enclosed in parenthesis\n" . "$herectx");
 				}
+
+			}
+
+			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 ($use_cnt > 1) {
+					CHECK("MACRO_ARG_REUSE",
+					      "Macro argument reuse '$arg' - possible side-effects?\n" . "$herectx");
+				}
 			}
 
 # check for line continuations outside of #defines