* [PATCH] ctype.h: remove duplicate isdigit() helper
@ 2020-10-26 16:23 Arnd Bergmann
2020-10-26 18:23 ` Nick Desaulniers
0 siblings, 1 reply; 3+ messages in thread
From: Arnd Bergmann @ 2020-10-26 16:23 UTC (permalink / raw)
To: Arnd Bergmann
Cc: Nathan Chancellor, Nick Desaulniers, linux-kernel,
clang-built-linux
From: Arnd Bergmann <arnd@arndb.de>
gcc warns a few thousand times about the isdigit() shadow:
include/linux/ctype.h:26:19: warning: declaration of 'isdigit' shadows a built-in function [-Wshadow]
As there is already a compiler builtin, just use that, and make
it clear we do that by defining a macro. Unfortunately, clang
does not have the isdigit() builtin, so this has to be conditional.
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
---
include/linux/ctype.h | 16 ++++++++++++----
1 file changed, 12 insertions(+), 4 deletions(-)
diff --git a/include/linux/ctype.h b/include/linux/ctype.h
index 363b004426db..c407acb258c2 100644
--- a/include/linux/ctype.h
+++ b/include/linux/ctype.h
@@ -23,10 +23,6 @@ extern const unsigned char _ctype[];
#define isalnum(c) ((__ismask(c)&(_U|_L|_D)) != 0)
#define isalpha(c) ((__ismask(c)&(_U|_L)) != 0)
#define iscntrl(c) ((__ismask(c)&(_C)) != 0)
-static inline int isdigit(int c)
-{
- return '0' <= c && c <= '9';
-}
#define isgraph(c) ((__ismask(c)&(_P|_U|_L|_D)) != 0)
#define islower(c) ((__ismask(c)&(_L)) != 0)
#define isprint(c) ((__ismask(c)&(_P|_U|_L|_D|_SP)) != 0)
@@ -39,6 +35,18 @@ static inline int isdigit(int c)
#define isascii(c) (((unsigned char)(c))<=0x7f)
#define toascii(c) (((unsigned char)(c))&0x7f)
+#if defined __has_builtin
+#if __has_builtin(__builtin_isdigit)
+#define isdigit(ch) __builtin_isdigit(ch)
+#endif
+#endif
+#ifndef isdigit
+static inline int isdigit(int c)
+{
+ return '0' <= c && c <= '9';
+}
+#endif
+
static inline unsigned char __tolower(unsigned char c)
{
if (isupper(c))
--
2.27.0
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH] ctype.h: remove duplicate isdigit() helper
2020-10-26 16:23 [PATCH] ctype.h: remove duplicate isdigit() helper Arnd Bergmann
@ 2020-10-26 18:23 ` Nick Desaulniers
2020-10-26 19:22 ` Arnd Bergmann
0 siblings, 1 reply; 3+ messages in thread
From: Nick Desaulniers @ 2020-10-26 18:23 UTC (permalink / raw)
To: Arnd Bergmann
Cc: Arnd Bergmann, Nathan Chancellor, LKML, clang-built-linux,
Miguel Ojeda
On Mon, Oct 26, 2020 at 9:23 AM Arnd Bergmann <arnd@kernel.org> wrote:
>
> From: Arnd Bergmann <arnd@arndb.de>
>
> gcc warns a few thousand times about the isdigit() shadow:
>
> include/linux/ctype.h:26:19: warning: declaration of 'isdigit' shadows a built-in function [-Wshadow]
Don't all functions defined here shadow builtins in GCC? Why is
`isdigit` unique? Is that because it's a `static inline` definition
vs a function like macro? If that's the case, what's the harm in
converting it to a function like macro if that silences the warning?
>
> As there is already a compiler builtin, just use that, and make
> it clear we do that by defining a macro. Unfortunately, clang
> does not have the isdigit() builtin, so this has to be conditional.
TODO(Nick): finish the Clang patch that implements that.
https://reviews.llvm.org/D86508
>
> Signed-off-by: Arnd Bergmann <arnd@arndb.de>
> ---
> include/linux/ctype.h | 16 ++++++++++++----
> 1 file changed, 12 insertions(+), 4 deletions(-)
>
> diff --git a/include/linux/ctype.h b/include/linux/ctype.h
> index 363b004426db..c407acb258c2 100644
> --- a/include/linux/ctype.h
> +++ b/include/linux/ctype.h
> @@ -23,10 +23,6 @@ extern const unsigned char _ctype[];
> #define isalnum(c) ((__ismask(c)&(_U|_L|_D)) != 0)
> #define isalpha(c) ((__ismask(c)&(_U|_L)) != 0)
> #define iscntrl(c) ((__ismask(c)&(_C)) != 0)
> -static inline int isdigit(int c)
> -{
> - return '0' <= c && c <= '9';
> -}
> #define isgraph(c) ((__ismask(c)&(_P|_U|_L|_D)) != 0)
> #define islower(c) ((__ismask(c)&(_L)) != 0)
> #define isprint(c) ((__ismask(c)&(_P|_U|_L|_D|_SP)) != 0)
> @@ -39,6 +35,18 @@ static inline int isdigit(int c)
> #define isascii(c) (((unsigned char)(c))<=0x7f)
> #define toascii(c) (((unsigned char)(c))&0x7f)
>
> +#if defined __has_builtin
#ifdef
only use `defined` explicitly when there's more than one condition
being checked with logical `&&` or `||`.
> +#if __has_builtin(__builtin_isdigit)
GCC only recently gained the `__has_builtin` macro (I filed the bug);
I would like to see something akin to
include/linux/compiler_attributes.h but using `__has_builtin` like
compiler_attributes.h uses `__has_attribute`. That way we avoid
spaghetti like this throughout the kernel.
> +#define isdigit(ch) __builtin_isdigit(ch)
> +#endif
> +#endif
> +#ifndef isdigit
> +static inline int isdigit(int c)
> +{
> + return '0' <= c && c <= '9';
> +}
> +#endif
> +
> static inline unsigned char __tolower(unsigned char c)
> {
> if (isupper(c))
> --
> 2.27.0
>
--
Thanks,
~Nick Desaulniers
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH] ctype.h: remove duplicate isdigit() helper
2020-10-26 18:23 ` Nick Desaulniers
@ 2020-10-26 19:22 ` Arnd Bergmann
0 siblings, 0 replies; 3+ messages in thread
From: Arnd Bergmann @ 2020-10-26 19:22 UTC (permalink / raw)
To: Nick Desaulniers; +Cc: Nathan Chancellor, LKML, clang-built-linux, Miguel Ojeda
On Mon, Oct 26, 2020 at 7:23 PM 'Nick Desaulniers' via Clang Built
Linux <clang-built-linux@googlegroups.com> wrote:
>
> On Mon, Oct 26, 2020 at 9:23 AM Arnd Bergmann <arnd@kernel.org> wrote:
> >
> > From: Arnd Bergmann <arnd@arndb.de>
> >
> > gcc warns a few thousand times about the isdigit() shadow:
> >
> > include/linux/ctype.h:26:19: warning: declaration of 'isdigit' shadows a built-in function [-Wshadow]
>
> Don't all functions defined here shadow builtins in GCC? Why is
> `isdigit` unique? Is that because it's a `static inline` definition
> vs a function like macro? If that's the case, what's the harm in
> converting it to a function like macro if that silences the warning?
It was originally a macro but got changed to an inline function in
1204c77f9b6a ("include/linux/ctype.h: make isdigit() table lookupless"),
apparently in order to avoid evaluating the argument more than once.
I suppose we could make it a statement expression with a local
variable like
#define isdigit(c) ({ __auto_type __c = (c); '0' <= __c && __c <= '9'; })
> > @@ -39,6 +35,18 @@ static inline int isdigit(int c)
> > #define isascii(c) (((unsigned char)(c))<=0x7f)
> > #define toascii(c) (((unsigned char)(c))&0x7f)
> >
> > +#if defined __has_builtin
>
> #ifdef
>
> only use `defined` explicitly when there's more than one condition
> being checked with logical `&&` or `||`.
>
> > +#if __has_builtin(__builtin_isdigit)
>
> GCC only recently gained the `__has_builtin` macro (I filed the bug);
> I would like to see something akin to
> include/linux/compiler_attributes.h but using `__has_builtin` like
> compiler_attributes.h uses `__has_attribute`. That way we avoid
> spaghetti like this throughout the kernel.
Ok. I've added a 'has_builtin()' macro (without underscores)
in linux/compiler.h in version 2. I don't use it anywhere else
in my current series, so there should be no dependencies.
Arnd
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