checkpatch: add --strict test for macro argument reuse

If a macro argument is used multiple times in the macro definition, the
macro argument may have an unexpected side-effect.

Add a test (MACRO_ARG_REUSE) for that condition which is only
emitted with command-line option --strict.

Link: http://lkml.kernel.org/r/b6d67a87cafcafd15499e91780dc63b15dec0aa0.1473744906.git.joe@perches.com
Signed-off-by: Joe Perches <joe@perches.com>
Cc: Andy Whitcroft <apw@canonical.com>
Cc: Julia Lawall <julia.lawall@lip6.fr>
Cc: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
index 3fa2b2e..f135f8e 100755 (executable)
--- a/scripts/checkpatch.pl
+++ b/scripts/checkpatch.pl
@@ -4753,7 +4753,17 @@ 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;
@@ -4789,6 +4799,15 @@ 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();
@@ -4804,13 +4823,6 @@ 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 ($dstat =~ /;/) {
                                        ERROR("MULTISTATEMENT_MACRO_USE_DO_WHILE",
@@ -4819,6 +4831,21 @@ sub process {
                                        ERROR("COMPLEX_MACRO",
                                              "Macros with complex values should be enclosed in parentheses\n" . "$herectx");
                                }
+
+                       }
+# check if any macro arguments are reused (ignore '...' and 'type')
+                       foreach my $arg (@def_args) {
+                               next if ($arg =~ /\.\.\./);
+                               next if ($arg =~ /^type$/);
+                               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");
+                               }
                        }
 
 # check for macros with flow control, but without ## concatenation