[PATCH] string: Use __restrict__ according to ISO/IEC 9899:TC3

[Guilhem Massol <guilhem.massol85@gmail.com>]

Source: https://www.open-std.org/jtc1/sc22/wg14/www/docs/n1256.pdf
Some functions in lib/string.c needs to use restrict according to sections:
* 7.21.2.1: memcpy
* 7.21.2.3: strcpy
* 7.21.2.4: strncpy
* 7.21.3.1: strcat
* 7.21.3.2: strncat

Signed-off-by: Guilhem Massol <guilhem.massol85@gmail.com>
---
 include/linux/string.h | 12 ++++++------
 lib/string.c           | 12 ++++++------
 2 files changed, 12 insertions(+), 12 deletions(-)

diff --git a/include/linux/string.h b/include/linux/string.h
index b850bd91b3d8..07679485104b 100644
--- a/include/linux/string.h
+++ b/include/linux/string.h
@@ -65,12 +65,12 @@ void *vmemdup_array_user(const void __user *src, size_t n, size_t size)
 #include <asm/string.h>
 
 #ifndef __HAVE_ARCH_STRCPY
-extern char * strcpy(char *,const char *);
+extern char * strcpy(char *__restrict__, const char *__restrict__);
 #endif
 #ifndef __HAVE_ARCH_STRNCPY
-extern char * strncpy(char *,const char *, __kernel_size_t);
+extern char * strncpy(char *__restrict__, const char *__restrict__, __kernel_size_t);
 #endif
-ssize_t sized_strscpy(char *, const char *, size_t);
+ssize_t sized_strscpy(char *__restrict__, const char *__restrict__, size_t);
 
 /*
  * The 2 argument style can only be used when dst is an array with a
@@ -149,10 +149,10 @@ ssize_t sized_strscpy(char *, const char *, size_t);
 	CONCATENATE(__strscpy_pad, COUNT_ARGS(__VA_ARGS__))(dst, src, __VA_ARGS__)
 
 #ifndef __HAVE_ARCH_STRCAT
-extern char * strcat(char *, const char *);
+extern char * strcat(char *__restrict__, const char *__restrict__);
 #endif
 #ifndef __HAVE_ARCH_STRNCAT
-extern char * strncat(char *, const char *, __kernel_size_t);
+extern char * strncat(char *__restrict__, const char *__restrict__, __kernel_size_t);
 #endif
 #ifndef __HAVE_ARCH_STRLCAT
 extern size_t strlcat(char *, const char *, __kernel_size_t);
@@ -257,7 +257,7 @@ extern void **__memcat_p(void **a, void **b);
 })
 
 #ifndef __HAVE_ARCH_MEMCPY
-extern void * memcpy(void *,const void *,__kernel_size_t);
+extern void * memcpy(void *__restrict__, const void *__restrict__, __kernel_size_t);
 #endif
 #ifndef __HAVE_ARCH_MEMMOVE
 extern void * memmove(void *,const void *,__kernel_size_t);
diff --git a/lib/string.c b/lib/string.c
index b632c71df1a5..9b492402ad04 100644
--- a/lib/string.c
+++ b/lib/string.c
@@ -77,7 +77,7 @@ EXPORT_SYMBOL(strcasecmp);
 #endif
 
 #ifndef __HAVE_ARCH_STRCPY
-char *strcpy(char *dest, const char *src)
+char *strcpy(char *__restrict__ dest, const char *__restrict__ src)
 {
 	char *tmp = dest;
 
@@ -89,7 +89,7 @@ EXPORT_SYMBOL(strcpy);
 #endif
 
 #ifndef __HAVE_ARCH_STRNCPY
-char *strncpy(char *dest, const char *src, size_t count)
+char *strncpy(char *__restrict__ dest, const char *__restrict__ src, size_t count)
 {
 	char *tmp = dest;
 
@@ -110,7 +110,7 @@ EXPORT_SYMBOL(strncpy);
 # define ALLBUTLAST_BYTE_MASK (~0ul >> 8)
 #endif
 
-ssize_t sized_strscpy(char *dest, const char *src, size_t count)
+ssize_t sized_strscpy(char *__restrict__ dest, const char *__restrict__ src, size_t count)
 {
 	const struct word_at_a_time constants = WORD_AT_A_TIME_CONSTANTS;
 	size_t max = count;
@@ -215,7 +215,7 @@ char *stpcpy(char *__restrict__ dest, const char *__restrict__ src)
 EXPORT_SYMBOL(stpcpy);
 
 #ifndef __HAVE_ARCH_STRCAT
-char *strcat(char *dest, const char *src)
+char *strcat(char *__restrict__ dest, const char *__restrict__ src)
 {
 	char *tmp = dest;
 
@@ -229,7 +229,7 @@ EXPORT_SYMBOL(strcat);
 #endif
 
 #ifndef __HAVE_ARCH_STRNCAT
-char *strncat(char *dest, const char *src, size_t count)
+char *strncat(char *__restrict__ dest, const char *__restrict__ src, size_t count)
 {
 	char *tmp = dest;
 
@@ -618,7 +618,7 @@ EXPORT_SYMBOL(memset64);
  * You should not use this function to access IO space, use memcpy_toio()
  * or memcpy_fromio() instead.
  */
-void *memcpy(void *dest, const void *src, size_t count)
+void *memcpy(void *__restrict__ dest, const void *__restrict__ src, size_t count)
 {
 	char *tmp = dest;
 	const char *s = src;
-- 
2.54.0