checkpatch: add test for comma use that should be semicolon

There are commas used as statement terminations that should typically have
used semicolons instead.  Only direct assignments or use of a single
function or value on a single line are detected by this test.

e.g.:
	foo = bar(),		/* typical use is semicolon not comma */
	bar = baz();

Add an imperfect test to detect these comma uses.

No false positives were found in testing, but many types of false
negatives are possible.

e.g.:
	foo = bar() + 1,	/* comma use, but not direct assignment */
	bar = baz();

Signed-off-by: Joe Perches <joe@perches.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Link: https://lkml.kernel.org/r/3bf27caf462007dfa75647b040ab3191374a59de.camel@perches.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
index 268028e382b5d4eb4478495eaed54af525c6a82f..74ccd122fc07e9af23fbad6009e8319e479f487a 100755 (executable)
--- a/scripts/checkpatch.pl
+++ b/scripts/checkpatch.pl
@@ -4940,6 +4940,17 @@ sub process {
                        }
                }
 
+# check if a statement with a comma should be two statements like:
+#      foo = bar(),    /* comma should be semicolon */
+#      bar = baz();
+               if (defined($stat) &&
+                   $stat =~ /^\+\s*(?:$Lval\s*$Assignment\s*)?$FuncArg\s*,\s*(?:$Lval\s*$Assignment\s*)?$FuncArg\s*;\s*$/) {
+                       my $cnt = statement_rawlines($stat);
+                       my $herectx = get_stat_here($linenr, $cnt, $here);
+                       WARN("SUSPECT_COMMA_SEMICOLON",
+                            "Possible comma where semicolon could be used\n" . $herectx);
+               }
+
 # return is not a function
                if (defined($stat) && $stat =~ /^.\s*return(\s*)\(/s) {
                        my $spacing = $1;