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From: Mac Xu <mac.xxn@outlook.com>
To: Joe Perches <joe@perches.com>, Barry Song <21cnbao@gmail.com>,
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 Lasse <charlemagnelasse@gmail.com>
Subject: Re: [PATCH v5 2/2] scripts: checkpatch: check unused parameters for
 function-like macro
Thread-Topic: [PATCH v5 2/2] scripts: checkpatch: check unused parameters for
 function-like macro
Thread-Index: AQHag9MBE6nuZEX6x0OitxYUtdLwcLFSs1aAgAFq0i6AABdXAIAA3lZU
Date: Tue, 2 Apr 2024 15:05:51 +0000
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=0A=
=0A=
> On Tue, 2024-04-02 at 00:16 +0000, Mac Xu wrote:=0A=
> > > On Mon, 2024-04-01 at 14:21 +1300, Barry Song wrote:=0A=
> > > > From: Xining Xu <mac.xxn@outlook.com>=0A=
> > > >=0A=
> > > > If function-like macros do not utilize a parameter, it might result=
 in a=0A=
> > > > build warning.  In our coding style guidelines, we advocate for uti=
lizing=0A=
> > > > static inline functions to replace such macros.  This patch verifie=
s=0A=
> > > > compliance with the new rule.=0A=
> > > >=0A=
> > > > For a macro such as the one below,=0A=
> > > >=0A=
> > > >  #define test(a) do { } while (0)=0A=
> > > >=0A=
> > > > The test result is as follows.=0A=
> > > >=0A=
> > > >  ERROR: Parameter 'a' is not used in function-like macro, please us=
e static=0A=
> > > >  inline instead=0A=
> > > >  #21: FILE: mm/init-mm.c:20:=0A=
> > > >  +#define test(a) do { } while (0)=0A=
> > >=0A=
> > > This is no longer true.=0A=
> > > Please update the ERROR->WARN and message as below=0A=
> > >=0A=
> > > Ideally, this would have an update to=0A=
> > > Documentation/dev-tools/checkpatch.rst=0A=
> > >=0A=
> > > to describe the new --verbose message type=0A=
> >=0A=
> > Hi Joe,=0A=
> >=0A=
> > Thank you for the comments, here's the code:=0A=
> >=0A=
> > +# check if this is an unused argument=0A=
> > +if ($define_stmt !~ /\b$arg\b/) {=0A=
> > +     WARN("MACRO_ARG_UNUSED",=0A=
> > +             "Argument '$arg' is not used in function-like macro\n" . =
"$herectx");=0A=
> > +}=0A=
> >=0A=
> > and here's the document for it which is inserted into the "Macros, Attr=
ibutes and=0A=
> > Symbols" section of checkpatch.rst starting from line 909:=0A=
> > +=0A=
> > +  **MACRO_ARG_UNUSED**=0A=
> > +    If function-like macros do not utilize a parameter, it might resul=
t=0A=
> > +    in a build warning. We advocate for utilizing static inline functi=
ons=0A=
> > +    to replace such macros.=0A=
> > +    For example, for a macro as below::=0A=
> > +=0A=
> > +      #define test(a) do { } while (0)=0A=
> > +=0A=
> > +    there would be a warning as below::=0A=
> > +=0A=
> > +      WARNING: Parameter 'a' is not used in function-like macro, pleas=
e use=0A=
> > +      static inline instead.=0A=
> >=0A=
> > Please let me know if the document needs further re-wording to make it =
helpful enough=0A=
> > to the readers.=0A=
> =0A=
> Hi again Xining.=0A=
> =0A=
> Thanks.=0A=
> =0A=
> That looks good but it doesn't match the script output=0A=
> which doesn't use ", please use static inline instead."=0A=
> (and I believe the script should not output that too)=0A=
> =0A=
> Another good thing would be to add a line like:=0A=
> =0A=
>         See: https://www.kernel.org/doc/html/latest/process/coding-style.=
html#macros-enums-and-rtl=0A=
> =0A=
> For example, from: checkpatch.rst=0A=
> =0A=
>   **ALLOC_SIZEOF_STRUCT**=0A=
>     The allocation style is bad.  In general for family of=0A=
>     allocation functions using sizeof() to get memory size,=0A=
>     constructs like::=0A=
> =0A=
>       p =3D alloc(sizeof(struct foo), ...)=0A=
> =0A=
>     should be::=0A=
> =0A=
>       p =3D alloc(sizeof(*p), ...)=0A=
> =0A=
>     See: https://www.kernel.org/doc/html/latest/process/coding-style.html=
#allocating-memory=0A=
> =0A=
> =0A=
=0A=
Hi again Joe,=0A=
=0A=
Thanks again for the detailed comments.=0A=
=0A=
Here's the code (which keeps unchanged):=0A=
+# check if this is an unused argument=0A=
+if ($define_stmt !~ /\b$arg\b/) {=0A=
+  WARN("MACRO_ARG_UNUSED",=0A=
+    "Argument '$arg' is not used in function-like macro\n" . "$herectx");=
=0A=
+}=0A=
=0A=
And here's the updated document, which drops the ", please use static inlin=
e instead" from the=0A=
warning message, and adds a link at the end of this document block:=0A=
+=0A=
+  **MACRO_ARG_UNUSED**=0A=
+    If function-like macros do not utilize a parameter, it might result=0A=
+    in a build warning. We advocate for utilizing static inline functions=
=0A=
+    to replace such macros.=0A=
+    For example, for a macro such as the one below::=0A=
+=0A=
+      #define test(a) do { } while (0)=0A=
+=0A=
+    there would be a warning like below::=0A=
+=0A=
+      WARNING: Parameter 'a' is not used in function-like macro.=0A=
+=0A=
+    See: https://www.kernel.org/doc/html/latest/process/coding-style.html#=
macros-enums-and-rtl=0A=
=0A=
=0A=
Regards,=0A=
Xining.=0A=
=0A=
=0A=