[PATCH] ctype.h: remove duplicate isdigit() helper

[Arnd Bergmann <arnd@kernel.org>]

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