Index: include/stdio.h
===================================================================
--- include/stdio.h
+++ include/stdio.h
@@ -250,12 +250,12 @@
 int	 fgetpos(FILE * __restrict, fpos_t * __restrict);
 char	*fgets(char * __restrict, int, FILE * __restrict);
 FILE	*fopen(const char * __restrict, const char * __restrict);
-int	 fprintf(FILE * __restrict, const char * __restrict, ...);
+int	 fprintf(FILE * __restrict, const char * _Nonnull __restrict, ...);
 int	 fputc(int, FILE *);
 int	 fputs(const char * __restrict, FILE * __restrict);
 size_t	 fread(void * __restrict, size_t, size_t, FILE * __restrict);
 FILE	*freopen(const char * __restrict, const char * __restrict, FILE * __restrict);
-int	 fscanf(FILE * __restrict, const char * __restrict, ...);
+int	 fscanf(FILE * __restrict, const char * _Nonnull __restrict, ...);
 int	 fseek(FILE *, long, int);
 int	 fsetpos(FILE *, const fpos_t *);
 long	 ftell(FILE *);
@@ -264,34 +264,34 @@
 int	 getchar(void);
 char	*gets(char *);
 void	 perror(const char *);
-int	 printf(const char * __restrict, ...);
+int	 printf(const char * _Nonnull __restrict, ...);
 int	 putc(int, FILE *);
 int	 putchar(int);
 int	 puts(const char *);
 int	 remove(const char *);
 int	 rename(const char *, const char *);
 void	 rewind(FILE *);
-int	 scanf(const char * __restrict, ...);
+int	 scanf(const char * _Nonnull __restrict, ...);
 void	 setbuf(FILE * __restrict, char * __restrict);
 int	 setvbuf(FILE * __restrict, char * __restrict, int, size_t);
-int	 sprintf(char * __restrict, const char * __restrict, ...);
-int	 sscanf(const char * __restrict, const char * __restrict, ...);
+int	 sprintf(char * __restrict, const char * _Nonnull __restrict, ...);
+int	 sscanf(const char * __restrict, const char * _Nonnull __restrict, ...);
 FILE	*tmpfile(void);
 char	*tmpnam(char *);
 int	 ungetc(int, FILE *);
-int	 vfprintf(FILE * __restrict, const char * __restrict,
+int	 vfprintf(FILE * __restrict, const char * _Nonnull __restrict,
 	    __va_list);
-int	 vprintf(const char * __restrict, __va_list);
-int	 vsprintf(char * __restrict, const char * __restrict,
+int	 vprintf(const char * _Nonnull __restrict, __va_list);
+int	 vsprintf(char * __restrict, const char * _Nonnull __restrict,
 	    __va_list);
 
 #if __ISO_C_VISIBLE >= 1999
-int	 snprintf(char * __restrict, size_t, const char * __restrict,
+int	 snprintf(char * __restrict, size_t, const char * _Nonnull __restrict,
 	    ...) __printflike(3, 4);
-int	 vfscanf(FILE * __restrict, const char * __restrict, __va_list)
+int	 vfscanf(FILE * __restrict, const char * _Nonnull __restrict, __va_list)
 	    __scanflike(2, 0);
-int	 vscanf(const char * __restrict, __va_list) __scanflike(1, 0);
-int	 vsnprintf(char * __restrict, size_t, const char * __restrict,
+int	 vscanf(const char * _Nonnull __restrict, __va_list) __scanflike(1, 0);
+int	 vsnprintf(char * __restrict, size_t, const char * _Nonnull __restrict,
 	    __va_list) __printflike(3, 0);
 int	 vsscanf(const char * __restrict, const char * __restrict, __va_list)
 	    __scanflike(2, 0);
Index: include/string.h
===================================================================
--- include/string.h
+++ include/string.h
@@ -37,6 +37,8 @@
 #include <sys/_null.h>
 #include <sys/_types.h>
 
+__NULLABILITY_PRAGMA_PUSH
+
 /*
  * Prototype functions which were historically defined in <string.h>, but
  * are required by POSIX to be prototyped in <strings.h>.
@@ -52,75 +54,83 @@
 
 __BEGIN_DECLS
 #if __XSI_VISIBLE >= 600
-void	*memccpy(void * __restrict, const void * __restrict, int, size_t);
+void	*memccpy(void * _Nonnull __restrict, const void * _Nonnull __restrict,
+    int, size_t);
 #endif
-void	*memchr(const void *, int, size_t) __pure;
+void	*memchr(const void * _Nonnull, int, size_t) __pure;
 #if __BSD_VISIBLE
-void	*memrchr(const void *, int, size_t) __pure;
+void	*memrchr(const void * _Nonnull, int, size_t) __pure;
 #endif
-int	 memcmp(const void *, const void *, size_t) __pure;
-void	*memcpy(void * __restrict, const void * __restrict, size_t);
+int	 memcmp(const void * _Nonnull, const void * _Nonnull, size_t) __pure;
+void	*memcpy(void * _Nonnull __restrict, const void * _Nonnull __restrict,
+    size_t);
 #if __BSD_VISIBLE
-void	*memmem(const void *, size_t, const void *, size_t) __pure;
+void	*memmem(const void * _Nonnull, size_t, const void * _Nonnull, size_t)
+    __pure;
 #endif
-void	*memmove(void *, const void *, size_t);
-void	*memset(void *, int, size_t);
+void	*memmove(void * _Nonnull, const void * _Nonnull, size_t);
+void	*memset(void * _Nonnull, int, size_t);
 #if __POSIX_VISIBLE >= 200809
-char	*stpcpy(char * __restrict, const char * __restrict);
-char	*stpncpy(char * __restrict, const char * __restrict, size_t);
+char	*stpcpy(char * _Nonnull __restrict, const char * _Nonnull __restrict);
+char	*stpncpy(char * _Nonnull __restrict, const char * _Nonnull __restrict,
+    size_t);
 #endif
 #if __BSD_VISIBLE
-char	*strcasestr(const char *, const char *) __pure;
+char	*strcasestr(const char * _Nonnull, const char * _Nonnull) __pure;
 #endif
-char	*strcat(char * __restrict, const char * __restrict);
+char	*strcat(char * _Nonnull __restrict, const char * _Nonnull __restrict);
 char	*strchr(const char *, int) __pure;
 #if __BSD_VISIBLE
-char	*strchrnul(const char*, int) __pure;
+char	*strchrnul(const char * _Nonnull, int) __pure;
 #endif
-int	 strcmp(const char *, const char *) __pure;
-int	 strcoll(const char *, const char *);
-char	*strcpy(char * __restrict, const char * __restrict);
-size_t	 strcspn(const char *, const char *) __pure;
+int	 strcmp(const char * _Nonnull, const char * _Nonnull) __pure;
+int	 strcoll(const char * _Nonnull, const char * _Nonnull);
+char	*strcpy(char * _Nonnull __restrict, const char * _Nonnull __restrict);
+size_t	 strcspn(const char * _Nonnull, const char * _Nonnull) __pure;
 #if __POSIX_VISIBLE >= 200112 || __XSI_VISIBLE
-char	*strdup(const char *) __malloc_like;
+char	*strdup(const char * _Nonnull) __malloc_like;
 #endif
 char	*strerror(int);
 #if __POSIX_VISIBLE >= 200112
 int	 strerror_r(int, char *, size_t);
 #endif
 #if __BSD_VISIBLE
-size_t	 strlcat(char * __restrict, const char * __restrict, size_t);
-size_t	 strlcpy(char * __restrict, const char * __restrict, size_t);
+size_t	 strlcat(char * _Nonnull __restrict, const char * _Nonnull __restrict,
+    size_t);
+size_t	 strlcpy(char * _Nonnull __restrict, const char * _Nonnull __restrict,
+    size_t);
 #endif
-size_t	 strlen(const char *) __pure;
+size_t	 strlen(const char * _Nonnull) __pure;
 #if __BSD_VISIBLE
 void	 strmode(int, char *);
 #endif
-char	*strncat(char * __restrict, const char * __restrict, size_t);
-int	 strncmp(const char *, const char *, size_t) __pure;
-char	*strncpy(char * __restrict, const char * __restrict, size_t);
+char	*strncat(char * _Nonnull __restrict, const char * _Nonnull __restrict,
+    size_t);
+int	 strncmp(const char * _Nonnull, const char * _Nonnull, size_t) __pure;
+char	*strncpy(char * _Nonnull __restrict, const char * _Nonnull __restrict,
+    size_t);
 #if __POSIX_VISIBLE >= 200809
-char	*strndup(const char *, size_t) __malloc_like;
-size_t	 strnlen(const char *, size_t) __pure;
+char	*strndup(const char * _Nonnull, size_t) __malloc_like;
+size_t	 strnlen(const char * _Nonnull, size_t) __pure;
 #endif
 #if __BSD_VISIBLE
 char	*strnstr(const char *, const char *, size_t) __pure;
 #endif
-char	*strpbrk(const char *, const char *) __pure;
-char	*strrchr(const char *, int) __pure;
+char	*strpbrk(const char * _Nonnull, const char * _Nonnull) __pure;
+char	*strrchr(const char * _Nonnull, int) __pure;
 #if __BSD_VISIBLE
-char	*strsep(char **, const char *);
+char	*strsep(char ** _Nonnull, const char * _Nonnull);
 #endif
 #if __POSIX_VISIBLE >= 200809
 char	*strsignal(int);
 #endif
-size_t	 strspn(const char *, const char *) __pure;
-char	*strstr(const char *, const char *) __pure;
-char	*strtok(char * __restrict, const char * __restrict);
+size_t	 strspn(const char * _Nonnull, const char * _Nonnull) __pure;
+char	*strstr(const char * _Nonnull, const char * _Nonnull) __pure;
+char	*strtok(char * __restrict, const char * _Nonnull __restrict);
 #if __POSIX_VISIBLE >= 199506 || __XSI_VISIBLE >= 500
-char	*strtok_r(char *, const char *, char **);
+char	*strtok_r(char *, const char * _Nonnull, char ** _Nonnull);
 #endif
-size_t	 strxfrm(char * __restrict, const char * __restrict, size_t);
+size_t	 strxfrm(char * __restrict, const char * _Nonnull __restrict, size_t);
 #if __BSD_VISIBLE
 
 #ifndef _SWAB_DECLARED
@@ -143,4 +153,6 @@
 #endif
 __END_DECLS
 
+__NULLABILITY_PRAGMA_POP
+
 #endif /* _STRING_H_ */