checkpatch: add checks for do {} while (0) macro misuses

These types of macros should not be used for either a single statement
nor should the macro end with a semi-colon.

Add tests for these conditions.

Signed-off-by: Joe Perches <joe@perches.com>
Cc: Andy Whitcroft <apw@canonical.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 39 insertions, 0 deletions

diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
index 40b0627aeb5e..913d6bdfdda3 100755
--- a/scripts/checkpatch.pl
+++ b/scripts/checkpatch.pl
@@ -2988,6 +2988,45 @@ sub process {
                         }
                 }
 
+# do {} while (0) macro tests:
+# single-statement macros do not need to be enclosed in do while (0) loop,
+# macro should not end with a semicolon
+                if ($^V && $^V ge 5.10.0 &&
+                    $realfile !~ m@/vmlinux.lds.h$@ &&
+                    $line =~ /^.\s*\#\s*define\s+$Ident(\()?/) {
+                        my $ln = $linenr;
+                        my $cnt = $realcnt;
+                        my ($off, $dstat, $dcond, $rest);
+                        my $ctx = '';
+                        ($dstat, $dcond, $ln, $cnt, $off) =
+                                ctx_statement_block($linenr, $realcnt, 0);
+                        $ctx = $dstat;
+
+                        $dstat =~ s/\\\n.//g;
+
+                        if ($dstat =~ /^\+\s*#\s*define\s+$Ident\s*${balanced_parens}\s*do\s*{(.*)\s*}\s*while\s*\(\s*0\s*\)\s*([;\s]*)\s*$/) {
+                                my $stmts = $2;
+                                my $semis = $3;
+
+                                $ctx =~ s/\n*$//;
+                                my $cnt = statement_rawlines($ctx);
+                                my $herectx = $here . "\n";
+
+                                for (my $n = 0; $n < $cnt; $n++) {
+                                        $herectx .= raw_line($linenr, $n) . "\n";
+                                }
+
+                                if (($stmts =~ tr/;/;/) == 1) {
+                                        WARN("SINGLE_STATEMENT_DO_WHILE_MACRO",
+                                             "Single statement macros should not use a do {} while (0) loop\n" . "$herectx");
+                                }
+                                if (defined $semis && $semis ne "") {
+                                        WARN("DO_WHILE_MACRO_WITH_TRAILING_SEMICOLON",
+                                             "do {} while (0) macros should not be semicolon terminated\n" . "$herectx");
+                                }
+                        }
+                }
+
 # make sure symbols are always wrapped with VMLINUX_SYMBOL() ...
 # all assignments may have only one of the following with an assignment:
 #       .