[Linux-kernel-mentees] [PATCH RFC] checkpatch: fix multi-statement macro checks

[Dwaipayan Ray]

On Thu, Oct 1, 2020 at 6:47 PM Joe Perches <joe at perches.com> wrote:
>
> On Thu, 2020-10-01 at 16:03 +0530, Dwaipayan Ray wrote:
> > Checkpatch.pl doesn't have a check for excluding while (...) {...}
> > blocks from MULTISTATEMENT_MACRO_USE_DO_WHILE error.
> >
> > For example, running checkpatch.pl on the file mm/access.c in the
> > kernel generates the following error:
> >
> > ERROR: Macros with complex values should be enclosed in parentheses
> > +#define copy_from_kernel_nofault_loop(dst, src, len, type, err_label)        \
> > +     while (len >= sizeof(type)) {                                   \
> > +             __get_kernel_nofault(dst, src, type, err_label);        \
> > +             dst += sizeof(type);                                    \
> > +             src += sizeof(type);                                    \
> > +             len -= sizeof(type);                                    \
> > +     }
> >
> > The error is misleading for this case. Enclosing it in parantheses
> > doesn't make any sense.
>
> OK
>
> > Checkpatch already has an exception list for such common macro types.
> > Added a new exception for while (...) {...} style blocks to the same.
> > This effectively fixed the wrong error message.
> []
> > diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
> []
> > @@ -5342,6 +5342,7 @@ sub process {
> >                           $dstat !~ /^\.$Ident\s*=/ &&                                # .foo =
> >                           $dstat !~ /^(?:\#\s*$Ident|\#\s*$Constant)\s*$/ &&          # stringification #foo
> >                           $dstat !~ /^do\s*$Constant\s*while\s*$Constant;?$/ &&       # do {...} while (...); // do {...} while (...)
> > +                         $dstat !~ /^while\s*$Constant\s*$Constant\s*$/ &&           # while (...) {...}
>
> Did you try to output $dstat for some matching cases?
> What was the $dstat value for the cases you tried?
>
>
Hi,
I did check $dstat values.

For example on file mm/maccess.c, there were two such macros:

Case 1:

$ctx:
+#define copy_from_kernel_nofault_loop(dst, src, len, type, err_label) \
+ while (len >= sizeof(type)) { \
+ __get_kernel_nofault(dst, src, type, err_label); \
+ dst += sizeof(type); \
+ src += sizeof(type); \
+ len -= sizeof(type); \
+ }

$dstat:
while 1 1

Case 2:

$ctx:
+#define copy_to_kernel_nofault_loop(dst, src, len, type, err_label) \
+ while (len >= sizeof(type)) { \
+ __put_kernel_nofault(dst, src, type, err_label); \
+ dst += sizeof(type); \
+ src += sizeof(type); \
+ len -= sizeof(type); \
+ }

$dstat:
while 1 1


Thanks,
Dwaipayan.