Index: include/string.h
===================================================================
--- include/string.h
+++ include/string.h
@@ -129,7 +129,7 @@
 char	*strstr(const char *, const char *) __pure;
 char	*strtok(char * __restrict, const char * __restrict);
 #if __POSIX_VISIBLE >= 199506 || __XSI_VISIBLE >= 500
-char	*strtok_r(char *, const char *, char **);
+char	*strtok_r(char * __restrict, const char * __restrict, char ** __restrict);
 #endif
 size_t	 strxfrm(char * __restrict, const char * __restrict, size_t);
 #if __BSD_VISIBLE
@@ -145,8 +145,8 @@
 void	 swab(const void * __restrict, void * __restrict, ssize_t);
 #endif /* _SWAB_DECLARED */
 
-int	 timingsafe_bcmp(const void *, const void *, size_t);
-int	 timingsafe_memcmp(const void *, const void *, size_t);
+int	 timingsafe_bcmp(const void *, const void *, size_t) __pure;
+int	 timingsafe_memcmp(const void *, const void *, size_t) __pure;
 #endif /* __BSD_VISIBLE */
 
 #if __POSIX_VISIBLE >= 200112 || defined(_XLOCALE_H_)
Index: lib/libc/string/memccpy.3
===================================================================
--- lib/libc/string/memccpy.3
+++ lib/libc/string/memccpy.3
@@ -28,7 +28,7 @@
 .\"     @(#)memccpy.3	8.1 (Berkeley) 6/9/93
 .\" $FreeBSD$
 .\"
-.Dd June 9, 1993
+.Dd July 4, 2021
 .Dt MEMCCPY 3
 .Os
 .Sh NAME
@@ -39,7 +39,7 @@
 .Sh SYNOPSIS
 .In string.h
 .Ft void *
-.Fn memccpy "void *dst" "const void *src" "int c" "size_t len"
+.Fn memccpy "void * restrict dst" "const void * restrict src" "int c" "size_t len"
 .Sh DESCRIPTION
 The
 .Fn memccpy
Index: lib/libc/string/mempcpy.c
===================================================================
--- lib/libc/string/mempcpy.c
+++ lib/libc/string/mempcpy.c
@@ -32,10 +32,12 @@
 #include <sys/cdefs.h>
 __FBSDID("$FreeBSD$");
 
+#include <sys/types.h>
+
 #include <string.h>
 
 void *
-mempcpy(void *__restrict dst, const void *__restrict src, size_t len)
+mempcpy(void * __restrict dst, const void * __restrict src, size_t len)
 {
-	return ((char *)memcpy(dst, src, len) + len);
+	return ((u_char *)memcpy(dst, src, len) + len);
 }
Index: lib/libc/string/strtok.3
===================================================================
--- lib/libc/string/strtok.3
+++ lib/libc/string/strtok.3
@@ -44,7 +44,7 @@
 .\"     @(#)strtok.3	8.2 (Berkeley) 2/3/94
 .\" $FreeBSD$
 .\"
-.Dd January 22, 2016
+.Dd July 4, 2021
 .Dt STRTOK 3
 .Os
 .Sh NAME
@@ -55,9 +55,9 @@
 .Sh SYNOPSIS
 .In string.h
 .Ft char *
-.Fn strtok "char *str" "const char *sep"
+.Fn strtok "char * restrict str" "const char * restrict sep"
 .Ft char *
-.Fn strtok_r "char *str" "const char *sep" "char **last"
+.Fn strtok_r "char * restrict str" "const char * restrict sep" "char ** restrict last"
 .Sh DESCRIPTION
 .Bf -symbolic
 This interface is obsoleted by
Index: lib/libc/string/strtok.c
===================================================================
--- lib/libc/string/strtok.c
+++ lib/libc/string/strtok.c
@@ -46,15 +46,16 @@
 #endif
 #include <string.h>
 
-char	*__strtok_r(char *, const char *, char **);
+char	*__strtok_r(char * __restrict, const char * __restrict, char ** __restrict);
 
 __weak_reference(__strtok_r, strtok_r);
 
 char *
-__strtok_r(char *s, const char *delim, char **last)
+__strtok_r(char * __restrict s, const char * __restrict delim, char ** __restrict last)
 {
-	char *spanp, *tok;
-	int c, sc;
+	const char *spanp;
+	char *tok;
+	char c, sc;
 
 	if (s == NULL && (s = *last) == NULL)
 		return (NULL);
@@ -64,12 +65,12 @@
 	 */
 cont:
 	c = *s++;
-	for (spanp = (char *)delim; (sc = *spanp++) != 0;) {
+	for (spanp = delim; (sc = *spanp++) != '\0';) {
 		if (c == sc)
 			goto cont;
 	}
 
-	if (c == 0) {		/* no non-delimiter characters */
+	if (c == '\0') { /* no non-delimiter characters */
 		*last = NULL;
 		return (NULL);
 	}
@@ -81,23 +82,23 @@
 	 */
 	for (;;) {
 		c = *s++;
-		spanp = (char *)delim;
+		spanp = delim;
 		do {
 			if ((sc = *spanp++) == c) {
-				if (c == 0)
+				if (c == '\0')
 					s = NULL;
 				else
 					s[-1] = '\0';
 				*last = s;
 				return (tok);
 			}
-		} while (sc != 0);
+		} while (sc != '\0');
 	}
 	/* NOTREACHED */
 }
 
 char *
-strtok(char *s, const char *delim)
+strtok(char * __restrict s, const char * __restrict delim)
 {
 	static char *last;
 
Index: lib/libc/string/strxfrm.3
===================================================================
--- lib/libc/string/strxfrm.3
+++ lib/libc/string/strxfrm.3
@@ -45,7 +45,7 @@
 .Ft size_t
 .Fn strxfrm "char * restrict dst" "const char * restrict src" "size_t n"
 .Ft size_t
-.Fn strxfrm_l "char * restrict dst" "const char *restrict src" "size_t n" "locale_t loc"
+.Fn strxfrm_l "char * restrict dst" "const char * restrict src" "size_t n" "locale_t loc"
 .Sh DESCRIPTION
 The
 .Fn strxfrm
Index: sys/libkern/strdup.c
===================================================================
--- sys/libkern/strdup.c
+++ sys/libkern/strdup.c
@@ -54,7 +54,7 @@
 }
 
 char *
-strdup(const char *string, struct malloc_type *type)
+strdup(const char * __restrict string, struct malloc_type *type)
 {
 
 	return (strdup_flags(string, type, M_WAITOK));
Index: sys/libkern/strlcat.c
===================================================================
--- sys/libkern/strlcat.c
+++ sys/libkern/strlcat.c
@@ -46,21 +46,21 @@
  * If retval >= siz, truncation occurred.
  */
 size_t
-strlcat(char *dst, const char *src, size_t siz)
+strlcat(char * __restrict dst, const char * __restrict src, size_t siz)
 {
 	char *d = dst;
 	const char *s = src;
 	size_t n = siz;
-	size_t dlen;
 
 	/* Find the end of dst and adjust bytes left but don't go past end */
-	while (n-- != 0 && *d != '\0')
-		d++;
-	dlen = d - dst;
-	n = siz - dlen;
+	for (;; ++d, --n) {
+		if (n == 0)
+			return (siz + strlen(s));
+		if (*d == '\0')
+			break;
+	}
+	const size_t dlen = siz - n;
 
-	if (n == 0)
-		return(dlen + strlen(s));
 	while (*s != '\0') {
 		if (n != 1) {
 			*d++ = *s;
@@ -70,5 +70,5 @@
 	}
 	*d = '\0';
 
-	return(dlen + (s - src));	/* count does not include NUL */
+	return (dlen + (s - src)); /* count does not include NUL */
 }
Index: sys/libkern/strncat.c
===================================================================
--- sys/libkern/strncat.c
+++ sys/libkern/strncat.c
@@ -43,19 +43,18 @@
  * are written at dst (at most n+1 bytes being appended).  Return dst.
  */
 char *
-strncat(char *dst, const char *src, size_t n)
+strncat(char * __restrict dst, const char * __restrict src, size_t n)
 {
 
 	if (n != 0) {
 		char *d = dst;
-		const char *s = src;
 
-		while (*d != 0)
+		while (*d != '\0')
 			d++;
 		do {
-			if ((*d = *s++) == '\0')
-				break;
-			d++;
+			if ((*d = *src) == '\0')
+				return (dst);
+			d++, src++;
 		} while (--n != 0);
 		*d = '\0';
 	}
Index: sys/sys/libkern.h
===================================================================
--- sys/sys/libkern.h
+++ sys/sys/libkern.h
@@ -129,7 +129,7 @@
 void	 arc4random_buf(void *, size_t);
 uint32_t arc4random_uniform(uint32_t);
 void	 arc4rand(void *, u_int, int);
-int	 timingsafe_bcmp(const void *, const void *, size_t);
+int	 timingsafe_bcmp(const void *, const void *, size_t) __pure;
 void	*bsearch(const void *, const void *, size_t,
 	    size_t, int (*)(const void *, const void *));
 #ifndef	HAVE_INLINE_FFS
@@ -158,8 +158,8 @@
 
 int	 fnmatch(const char *, const char *, int);
 int	 locc(int, char *, u_int);
-void	*memchr(const void *s, int c, size_t n);
-void	*memcchr(const void *s, int c, size_t n);
+void	*memchr(const void *s, int c, size_t n) __pure;
+void	*memcchr(const void *s, int c, size_t n) __pure;
 void	*memmem(const void *l, size_t l_len, const void *s, size_t s_len);
 void	 qsort(void *base, size_t nmemb, size_t size,
 	    int (*compar)(const void *, const void *));
@@ -167,40 +167,40 @@
 	    int (*compar)(void *, const void *, const void *));
 u_long	 random(void);
 int	 scanc(u_int, const u_char *, const u_char *, int);
-int	 strcasecmp(const char *, const char *);
-char	*strcasestr(const char *, const char *);
+int	 strcasecmp(const char *, const char *) __pure;
+char	*strcasestr(const char *, const char *) __pure;
 char	*strcat(char * __restrict, const char * __restrict);
-char	*strchr(const char *, int);
-char	*strchrnul(const char *, int);
-int	 strcmp(const char *, const char *);
+char	*strchr(const char *, int) __pure;
+char	*strchrnul(const char *, int) __pure;
+int	 strcmp(const char *, const char *) __pure;
 char	*strcpy(char * __restrict, const char * __restrict);
-char	*strdup_flags(const char *__restrict, struct malloc_type *, int);
 size_t	 strcspn(const char *, const char *) __pure;
-char	*strdup(const char *__restrict, struct malloc_type *);
-char	*strncat(char *, const char *, size_t);
-char	*strndup(const char *__restrict, size_t, struct malloc_type *);
-size_t	 strlcat(char *, const char *, size_t);
-size_t	 strlcpy(char *, const char *, size_t);
-size_t	 strlen(const char *);
-int	 strncasecmp(const char *, const char *, size_t);
-int	 strncmp(const char *, const char *, size_t);
+char	*strdup_flags(const char * __restrict, struct malloc_type *, int) __malloc_like;
+char	*strdup(const char * __restrict, struct malloc_type *) __malloc_like;
+char	*strncat(char * __restrict, const char * __restrict, size_t);
+char	*strndup(const char * __restrict, size_t, struct malloc_type *) __malloc_like;
+size_t	 strlcat(char * __restrict, const char * __restrict, size_t);
+size_t	 strlcpy(char * __restrict, const char * __restrict, size_t);
+size_t	 strlen(const char *) __pure;
+int	 strncasecmp(const char *, const char *, size_t) __pure;
+int	 strncmp(const char *, const char *, size_t) __pure;
 char	*strncpy(char * __restrict, const char * __restrict, size_t);
-size_t	 strnlen(const char *, size_t);
+size_t	 strnlen(const char *, size_t) __pure;
 char	*strnstr(const char *, const char *, size_t);
-char	*strrchr(const char *, int);
+char	*strrchr(const char *, int) __pure;
 char	*strsep(char **, const char *delim);
-size_t	 strspn(const char *, const char *);
-char	*strstr(const char *, const char *);
-int	 strvalid(const char *, size_t);
+size_t	 strspn(const char *, const char *) __pure;
+char	*strstr(const char *, const char *) __pure;
+int	 strvalid(const char *, size_t) __pure;
 
 #ifdef SAN_NEEDS_INTERCEPTORS
 #ifndef SAN_INTERCEPTOR
 #define	SAN_INTERCEPTOR(func)	\
 	__CONCAT(SAN_INTERCEPTOR_PREFIX, __CONCAT(_, func))
 #endif
-char	*SAN_INTERCEPTOR(strcpy)(char *, const char *);
-int	SAN_INTERCEPTOR(strcmp)(const char *, const char *);
-size_t	SAN_INTERCEPTOR(strlen)(const char *);
+char	*SAN_INTERCEPTOR(strcpy)(char * __restrict, const char * __restrict);
+int	SAN_INTERCEPTOR(strcmp)(const char *, const char *) __pure;
+size_t	SAN_INTERCEPTOR(strlen)(const char *) __pure;
 #ifndef SAN_RUNTIME
 #define	strcpy(d, s)	SAN_INTERCEPTOR(strcpy)((d), (s))
 #define	strcmp(s1, s2)	SAN_INTERCEPTOR(strcmp)((s1), (s2))