diff --git a/libc/include/dlfcn.h b/libc/include/dlfcn.h
index 5dc8350..a53f664 100644
--- a/libc/include/dlfcn.h
+++ b/libc/include/dlfcn.h
@@ -25,6 +25,7 @@
  * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  * SUCH DAMAGE.
  */
+
 #ifndef __DLFCN_H__
 #define __DLFCN_H__
 
@@ -32,24 +33,28 @@
 
 __BEGIN_DECLS
 
+#if defined(__clang__)
+#pragma clang diagnostic push
+#pragma clang diagnostic ignored "-Wnullability-completeness"
+#endif
+
 typedef struct {
-    const char *dli_fname;  /* Pathname of shared object that
-                               contains address */
-    void       *dli_fbase;  /* Address at which shared object
-                               is loaded */
-    const char *dli_sname;  /* Name of nearest symbol with address
-                               lower than addr */
-    void       *dli_saddr;  /* Exact address of symbol named
-                               in dli_sname */
+  /* Pathname of shared object that contains address. */
+  const char* dli_fname;
+  /* Address at which shared object is loaded. */
+  void* dli_fbase;
+  /* Name of nearest symbol with address lower than addr. */
+  const char* dli_sname;
+  /* Exact address of symbol named in dli_sname. */
+  void* dli_saddr;
 } Dl_info;
 
-extern void* dlopen(const char*  filename, int flag);
-extern int dlclose(void*  handle);
-extern const char* dlerror(void);
-extern void* dlsym(void* handle, const char* _Nonnull symbol);
-extern void* dlvsym(void* handle, const char* _Nonnull symbol, const char* _Nonnull version)
-  __INTRODUCED_IN(24);
-extern int dladdr(const void* addr, Dl_info *info);
+void* dlopen(const char* filename, int flag);
+int dlclose(void* _Nonnull handle);
+const char* dlerror(void);
+void* dlsym(void* handle, const char* _Nonnull symbol);
+void* dlvsym(void* handle, const char* _Nonnull symbol, const char* _Nonnull version) __INTRODUCED_IN(24);
+int dladdr(const void* addr, Dl_info* _Nonnull info);
 
 enum {
 #if defined(__LP64__)
@@ -70,11 +75,15 @@
 };
 
 #if defined (__LP64__)
-#define RTLD_DEFAULT  ((void*) 0)
-#define RTLD_NEXT     ((void*) -1L)
+#define RTLD_DEFAULT  __BIONIC_CAST(reinterpret_cast, void*, 0)
+#define RTLD_NEXT     __BIONIC_CAST(reinterpret_cast, void*, -1L)
 #else
-#define RTLD_DEFAULT  ((void*) 0xffffffff)
-#define RTLD_NEXT     ((void*) 0xfffffffe)
+#define RTLD_DEFAULT  __BIONIC_CAST(reinterpret_cast, void*, 0xffffffff)
+#define RTLD_NEXT     __BIONIC_CAST(reinterpret_cast, void*, 0xfffffffe)
+#endif
+
+#if defined(__clang__)
+#pragma clang diagnostic pop
 #endif
 
 __END_DECLS
diff --git a/libc/include/error.h b/libc/include/error.h
index 18ce379..05ce35d 100644
--- a/libc/include/error.h
+++ b/libc/include/error.h
@@ -33,14 +33,14 @@
 
 __BEGIN_DECLS
 
-void error(int, int, const char* _Nonnull, ...) __printflike(3, 4) __INTRODUCED_IN(23);
-void error_at_line(int, int, const char*, unsigned int, const char* _Nonnull, ...) __printflike(5, 6)
-  __INTRODUCED_IN(23);
-
-extern void (*error_print_progname)(void) __INTRODUCED_IN(23);
+extern void (* _Nullable error_print_progname)(void) __INTRODUCED_IN(23);
 extern unsigned int error_message_count __INTRODUCED_IN(23);
 extern int error_one_per_line __INTRODUCED_IN(23);
 
+void error(int, int, const char* _Nonnull, ...) __printflike(3, 4) __INTRODUCED_IN(23);
+void error_at_line(int, int, const char* _Nullable, unsigned int, const char* _Nonnull, ...)
+    __printflike(5, 6) __INTRODUCED_IN(23);
+
 __END_DECLS
 
 #endif
diff --git a/libc/include/grp.h b/libc/include/grp.h
index 498d1b8..1d38265 100644
--- a/libc/include/grp.h
+++ b/libc/include/grp.h
@@ -39,19 +39,19 @@
 #include <sys/types.h>
 
 struct group {
-    char* gr_name; /* group name */
-    char* gr_passwd; /* group password */
-    gid_t gr_gid; /* group id */
-    char** gr_mem; /* group members */
+  char* gr_name; /* group name */
+  char* gr_passwd; /* group password */
+  gid_t gr_gid; /* group id */
+  char** gr_mem; /* group members */
 };
 
 __BEGIN_DECLS
+
 struct group* getgrgid(gid_t);
 struct group* getgrnam(const char*);
 
-/* Android has thousands and thousands of ids to iterate through. */
-struct group* getgrent(void)
-  __attribute__((warning("getgrent is inefficient on Android"))) __INTRODUCED_IN_FUTURE;
+/* Note: Android has thousands and thousands of ids to iterate through. */
+struct group* getgrent(void) __INTRODUCED_IN_FUTURE;
 
 void setgrent(void) __INTRODUCED_IN_FUTURE;
 void endgrent(void) __INTRODUCED_IN_FUTURE;
diff --git a/libc/include/locale.h b/libc/include/locale.h
index daef18f..a8f03bc 100644
--- a/libc/include/locale.h
+++ b/libc/include/locale.h
@@ -25,6 +25,7 @@
  * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  * SUCH DAMAGE.
  */
+
 #ifndef _LOCALE_H_
 #define _LOCALE_H_
 
@@ -66,30 +67,30 @@
                      LC_IDENTIFICATION_MASK)
 
 struct lconv {
-    char* decimal_point;
-    char* thousands_sep;
-    char* grouping;
-    char* int_curr_symbol;
-    char* currency_symbol;
-    char* mon_decimal_point;
-    char* mon_thousands_sep;
-    char* mon_grouping;
-    char* positive_sign;
-    char* negative_sign;
-    char  int_frac_digits;
-    char  frac_digits;
-    char  p_cs_precedes;
-    char  p_sep_by_space;
-    char  n_cs_precedes;
-    char  n_sep_by_space;
-    char  p_sign_posn;
-    char  n_sign_posn;
-    char  int_p_cs_precedes;
-    char  int_p_sep_by_space;
-    char  int_n_cs_precedes;
-    char  int_n_sep_by_space;
-    char  int_p_sign_posn;
-    char  int_n_sign_posn;
+  char* decimal_point;
+  char* thousands_sep;
+  char* grouping;
+  char* int_curr_symbol;
+  char* currency_symbol;
+  char* mon_decimal_point;
+  char* mon_thousands_sep;
+  char* mon_grouping;
+  char* positive_sign;
+  char* negative_sign;
+  char int_frac_digits;
+  char frac_digits;
+  char p_cs_precedes;
+  char p_sep_by_space;
+  char n_cs_precedes;
+  char n_sep_by_space;
+  char p_sign_posn;
+  char n_sign_posn;
+  char int_p_cs_precedes;
+  char int_p_sep_by_space;
+  char int_n_cs_precedes;
+  char int_n_sep_by_space;
+  char int_p_sign_posn;
+  char int_n_sign_posn;
 };
 
 struct lconv* localeconv(void) __INTRODUCED_IN(21);
@@ -100,7 +101,7 @@
 char* setlocale(int, const char*);
 locale_t uselocale(locale_t) __INTRODUCED_IN(21);
 
-#define LC_GLOBAL_LOCALE ((locale_t) -1L)
+#define LC_GLOBAL_LOCALE __BIONIC_CAST(reinterpret_cast, locale_t, -1L)
 
 __END_DECLS
 
diff --git a/libc/include/malloc.h b/libc/include/malloc.h
index 8e6cef9..d9bb315 100644
--- a/libc/include/malloc.h
+++ b/libc/include/malloc.h
@@ -23,12 +23,12 @@
 
 __BEGIN_DECLS
 
-extern void* malloc(size_t byte_count) __mallocfunc __wur __attribute__((alloc_size(1)));
-extern void* calloc(size_t item_count, size_t item_size) __mallocfunc __wur __attribute__((alloc_size(1,2)));
-extern void* realloc(void* p, size_t byte_count) __wur __attribute__((alloc_size(2)));
+extern void* malloc(size_t byte_count) __mallocfunc __wur;
+extern void* calloc(size_t item_count, size_t item_size) __mallocfunc __wur;
+extern void* realloc(void* p, size_t byte_count) __wur;
 extern void free(void* p);
 
-extern void* memalign(size_t alignment, size_t byte_count) __mallocfunc __wur __attribute__((alloc_size(2)));
+extern void* memalign(size_t alignment, size_t byte_count) __mallocfunc __wur;
 extern size_t malloc_usable_size(const void* p) __INTRODUCED_IN(17);
 
 #ifndef STRUCT_MALLINFO_DECLARED
diff --git a/libc/include/netinet/in6.h b/libc/include/netinet/in6.h
index 879ac75..ae20f83 100644
--- a/libc/include/netinet/in6.h
+++ b/libc/include/netinet/in6.h
@@ -29,33 +29,34 @@
 #ifndef _NETINET_IN6_H
 #define _NETINET_IN6_H
 
+#include <sys/cdefs.h>
+
 #include <linux/in6.h>
 
 #define IN6_IS_ADDR_UNSPECIFIED(a) \
-  ((*(const uint32_t*)(&(a)->s6_addr[0]) == 0) && \
-   (*(const uint32_t*)(&(a)->s6_addr[4]) == 0) && \
-   (*(const uint32_t*)(&(a)->s6_addr[8]) == 0) && \
-   (*(const uint32_t*)(&(a)->s6_addr[12]) == 0))
+  ((((a)->s6_addr32[0]) == 0) && \
+   (((a)->s6_addr32[1]) == 0) && \
+   (((a)->s6_addr32[2]) == 0) && \
+   (((a)->s6_addr32[3]) == 0))
 
 #define IN6_IS_ADDR_LOOPBACK(a) \
-  ((*(const uint32_t*)(&(a)->s6_addr[0]) == 0) && \
-   (*(const uint32_t*)(&(a)->s6_addr[4]) == 0) && \
-   (*(const uint32_t*)(&(a)->s6_addr[8]) == 0) && \
-   (*(const uint32_t*)(&(a)->s6_addr[12]) == ntohl(1)))
+  ((((a)->s6_addr32[0]) == 0) && \
+   (((a)->s6_addr32[1]) == 0) && \
+   (((a)->s6_addr32[2]) == 0) && \
+   (((a)->s6_addr32[3]) == ntohl(1)))
 
 #define IN6_IS_ADDR_V4COMPAT(a) \
-  ((*(const uint32_t*)(&(a)->s6_addr[0]) == 0) && \
-   (*(const uint32_t*)(&(a)->s6_addr[4]) == 0) && \
-   (*(const uint32_t*)(&(a)->s6_addr[8]) == 0) && \
-   (*(const uint32_t*)(&(a)->s6_addr[12]) != 0) && \
-   (*(const uint32_t*)(&(a)->s6_addr[12]) != ntohl(1)))
+  ((((a)->s6_addr32[0]) == 0) && \
+   (((a)->s6_addr32[1]) == 0) && \
+   (((a)->s6_addr32[2]) == 0) && \
+   (((a)->s6_addr32[3]) != 0) && (((a)->s6_addr32[3]) != ntohl(1)))
 
 #define IN6_IS_ADDR_V4MAPPED(a) \
-  ((*(const uint32_t*)(&(a)->s6_addr[0]) == 0) && \
-   (*(const uint32_t*)(&(a)->s6_addr[4]) == 0) && \
-   (*(const uint32_t*)(&(a)->s6_addr[8]) == ntohl(0x0000ffff)))
+  ((((a)->s6_addr32[0]) == 0) && \
+   (((a)->s6_addr32[1]) == 0) && \
+   (((a)->s6_addr32[2]) == ntohl(0x0000ffff)))
 
-#define __bionic_s6_addr(a) ((const uint8_t*)(a))
+#define __bionic_s6_addr(a) __BIONIC_CAST(reinterpret_cast, const uint8_t*, a)
 
 #define IN6_IS_ADDR_LINKLOCAL(a) \
   ((__bionic_s6_addr(a)[0] == 0xfe) && ((__bionic_s6_addr(a)[1] & 0xc0) == 0x80))
diff --git a/libc/include/pthread.h b/libc/include/pthread.h
index 3262bd1..1153695 100644
--- a/libc/include/pthread.h
+++ b/libc/include/pthread.h
@@ -36,6 +36,13 @@
 #include <sys/types.h>
 #include <time.h>
 
+__BEGIN_DECLS
+
+#if defined(__clang__)
+#pragma clang diagnostic push
+#pragma clang diagnostic ignored "-Wnullability-completeness"
+#endif
+
 typedef struct {
 #if defined(__LP64__)
   int32_t __private[10];
@@ -131,8 +138,6 @@
 #define PTHREAD_SCOPE_SYSTEM     0
 #define PTHREAD_SCOPE_PROCESS    1
 
-__BEGIN_DECLS
-
 int pthread_atfork(void (*)(void), void (*)(void), void (*)(void)) __INTRODUCED_IN(12);
 
 int pthread_attr_destroy(pthread_attr_t* _Nonnull);
@@ -263,8 +268,8 @@
   void*                         __cleanup_arg;
 } __pthread_cleanup_t;
 
-extern void __pthread_cleanup_push(__pthread_cleanup_t* c, __pthread_cleanup_func_t, void*);
-extern void __pthread_cleanup_pop(__pthread_cleanup_t*, int);
+void __pthread_cleanup_push(__pthread_cleanup_t* c, __pthread_cleanup_func_t, void*);
+void __pthread_cleanup_pop(__pthread_cleanup_t*, int);
 
 /* Believe or not, the definitions of pthread_cleanup_push and
  * pthread_cleanup_pop below are correct. Posix states that these
@@ -281,6 +286,10 @@
         __pthread_cleanup_pop( &__cleanup, (execute)); \
     } while (0);                                       \
 
+#if defined(__clang__)
+#pragma clang diagnostic pop
+#endif
+
 __END_DECLS
 
 #endif /* _PTHREAD_H_ */
diff --git a/libc/include/pwd.h b/libc/include/pwd.h
index 0b39a78..a686d05 100644
--- a/libc/include/pwd.h
+++ b/libc/include/pwd.h
@@ -63,6 +63,8 @@
 #include <sys/cdefs.h>
 #include <sys/types.h>
 
+__BEGIN_DECLS
+
 #define _PATH_PASSWD        "/etc/passwd"
 #define _PATH_MASTERPASSWD  "/etc/master.passwd"
 #define _PATH_MASTERPASSWD_LOCK "/etc/ptmp"
@@ -96,8 +98,7 @@
 #define _PASSWORD_WARNDAYS  14  /* days to warn about expiry */
 #define _PASSWORD_CHGNOW    -1  /* special day to force password change at next login */
 
-struct passwd
-{
+struct passwd {
   char* pw_name;
   char* pw_passwd;
   uid_t pw_uid;
@@ -112,13 +113,12 @@
   char* pw_shell;
 };
 
-__BEGIN_DECLS
-
 struct passwd* getpwnam(const char*);
 struct passwd* getpwuid(uid_t);
-/* Android has thousands and thousands of ids to iterate through */
-struct passwd* getpwent(void)
-  __attribute__((warning("getpwent is inefficient on Android"))) __INTRODUCED_IN_FUTURE;
+
+/* Note: Android has thousands and thousands of ids to iterate through */
+struct passwd* getpwent(void) __INTRODUCED_IN_FUTURE;
+
 void setpwent(void) __INTRODUCED_IN_FUTURE;
 void endpwent(void) __INTRODUCED_IN_FUTURE;
 
diff --git a/libc/include/signal.h b/libc/include/signal.h
index 3905d86..8d9d63f 100644
--- a/libc/include/signal.h
+++ b/libc/include/signal.h
@@ -53,6 +53,11 @@
 
 __BEGIN_DECLS
 
+#if defined(__clang__)
+#pragma clang diagnostic push
+#pragma clang diagnostic ignored "-Wnullability-completeness"
+#endif
+
 typedef int sig_atomic_t;
 
 /* The arm and x86 kernel header files don't define _NSIG. */
@@ -67,16 +72,16 @@
 /* The kernel headers define SIG_DFL (0) and SIG_IGN (1) but not SIG_HOLD, since
  * SIG_HOLD is only used by the deprecated SysV signal API.
  */
-#define SIG_HOLD ((sighandler_t)(uintptr_t)2)
+#define SIG_HOLD __BIONIC_CAST(reinterpret_cast, sighandler_t, 2)
 
 /* We take a few real-time signals for ourselves. May as well use the same names as glibc. */
 #define SIGRTMIN (__libc_current_sigrtmin())
 #define SIGRTMAX (__libc_current_sigrtmax())
-extern int __libc_current_sigrtmin(void) __INTRODUCED_IN(21);
-extern int __libc_current_sigrtmax(void) __INTRODUCED_IN(21);
+int __libc_current_sigrtmin(void) __INTRODUCED_IN(21);
+int __libc_current_sigrtmax(void) __INTRODUCED_IN(21);
 
-extern const char* const sys_siglist[];
-extern const char* const sys_signame[]; /* BSD compatibility. */
+extern const char* const sys_siglist[_NSIG];
+extern const char* const sys_signame[_NSIG]; /* BSD compatibility. */
 
 typedef __sighandler_t sig_t; /* BSD compatibility. */
 typedef __sighandler_t sighandler_t; /* glibc compatibility. */
@@ -108,51 +113,55 @@
 
 #endif
 
-extern int sigaction(int, const struct sigaction*, struct sigaction*);
+int sigaction(int, const struct sigaction*, struct sigaction*);
 
 __BIONIC_LEGACY_INLINE sighandler_t signal(int, sighandler_t);
 
-extern int siginterrupt(int, int);
+int siginterrupt(int, int);
 
-__BIONIC_LEGACY_INLINE int sigaddset(sigset_t*, int);
-__BIONIC_LEGACY_INLINE int sigdelset(sigset_t*, int);
-__BIONIC_LEGACY_INLINE int sigemptyset(sigset_t*);
-__BIONIC_LEGACY_INLINE int sigfillset(sigset_t*);
-__BIONIC_LEGACY_INLINE int sigismember(const sigset_t*, int);
+__BIONIC_LEGACY_INLINE int sigaddset(sigset_t* _Nonnull, int);
+__BIONIC_LEGACY_INLINE int sigdelset(sigset_t* _Nonnull, int);
+__BIONIC_LEGACY_INLINE int sigemptyset(sigset_t* _Nonnull);
+__BIONIC_LEGACY_INLINE int sigfillset(sigset_t* _Nonnull);
+__BIONIC_LEGACY_INLINE int sigismember(const sigset_t* _Nonnull, int);
 
-extern int sigpending(sigset_t* _Nonnull);
-extern int sigprocmask(int, const sigset_t*, sigset_t*);
-extern int sigsuspend(const sigset_t* _Nonnull);
-extern int sigwait(const sigset_t* _Nonnull, int* _Nonnull);
+int sigpending(sigset_t* _Nonnull);
+int sigprocmask(int, const sigset_t*, sigset_t*);
+int sigsuspend(const sigset_t* _Nonnull);
+int sigwait(const sigset_t* _Nonnull, int* _Nonnull);
 
-extern int sighold(int)
+int sighold(int)
   __attribute__((deprecated("use sigprocmask() or pthread_sigmask() instead")))
   __INTRODUCED_IN_FUTURE;
-extern int sigignore(int)
+int sigignore(int)
   __attribute__((deprecated("use sigaction() instead"))) __INTRODUCED_IN_FUTURE;
-extern int sigpause(int)
+int sigpause(int)
   __attribute__((deprecated("use sigsuspend() instead"))) __INTRODUCED_IN_FUTURE;
-extern int sigrelse(int)
+int sigrelse(int)
   __attribute__((deprecated("use sigprocmask() or pthread_sigmask() instead")))
   __INTRODUCED_IN_FUTURE;
-extern sighandler_t sigset(int, sighandler_t)
+sighandler_t sigset(int, sighandler_t)
   __attribute__((deprecated("use sigaction() instead"))) __INTRODUCED_IN_FUTURE;
 
-extern int raise(int);
-extern int kill(pid_t, int);
-extern int killpg(int, int);
+int raise(int);
+int kill(pid_t, int);
+int killpg(int, int);
 
-extern int sigaltstack(const stack_t*, stack_t*);
+int sigaltstack(const stack_t*, stack_t*);
 
-extern void psiginfo(const siginfo_t*, const char*) __INTRODUCED_IN(17);
-extern void psignal(int, const char*) __INTRODUCED_IN(17);
+void psiginfo(const siginfo_t*, const char*) __INTRODUCED_IN(17);
+void psignal(int, const char*) __INTRODUCED_IN(17);
 
-extern int pthread_kill(pthread_t, int);
-extern int pthread_sigmask(int, const sigset_t*, sigset_t*);
+int pthread_kill(pthread_t, int);
+int pthread_sigmask(int, const sigset_t*, sigset_t*);
 
-extern int sigqueue(pid_t, int, const union sigval) __INTRODUCED_IN(23);
-extern int sigtimedwait(const sigset_t*, siginfo_t*, const struct timespec*) __INTRODUCED_IN(23);
-extern int sigwaitinfo(const sigset_t*, siginfo_t*) __INTRODUCED_IN(23);
+int sigqueue(pid_t, int, const union sigval) __INTRODUCED_IN(23);
+int sigtimedwait(const sigset_t* _Nonnull, siginfo_t*, const struct timespec*) __INTRODUCED_IN(23);
+int sigwaitinfo(const sigset_t* _Nonnull, siginfo_t*) __INTRODUCED_IN(23);
+
+#if defined(__clang__)
+#pragma clang diagnostic pop
+#endif
 
 __END_DECLS
 
diff --git a/libc/include/stdint.h b/libc/include/stdint.h
index a66e21e..0ad27f1 100644
--- a/libc/include/stdint.h
+++ b/libc/include/stdint.h
@@ -32,7 +32,7 @@
 #include <bits/wchar_limits.h>
 #include <stddef.h>
 
-typedef __signed char __int8_t;
+typedef signed char __int8_t;
 typedef unsigned char __uint8_t;
 typedef short __int16_t;
 typedef unsigned short __uint16_t;
diff --git a/libc/include/stdio.h b/libc/include/stdio.h
index 621caa8..c876b0f 100644
--- a/libc/include/stdio.h
+++ b/libc/include/stdio.h
@@ -49,6 +49,11 @@
 
 __BEGIN_DECLS
 
+#if defined(__clang__)
+#pragma clang diagnostic push
+#pragma clang diagnostic ignored "-Wnullability-completeness"
+#endif
+
 typedef off_t fpos_t;
 typedef off64_t fpos64_t;
 
@@ -147,8 +152,8 @@
 #if __STDC_VERSION__ < 201112L
 char* gets(char*) __attribute__((deprecated("gets is unsafe, use fgets instead")));
 #endif
-int sprintf(char* __restrict, const char* __restrict _Nonnull, ...) __printflike(2, 3) __warnattr("sprintf is often misused; please use snprintf");
-int vsprintf(char* __restrict, const char* __restrict _Nonnull, __va_list) __printflike(2, 0) __warnattr("vsprintf is often misused; please use vsnprintf");
+int sprintf(char* __restrict, const char* __restrict _Nonnull, ...) __printflike(2, 3);
+int vsprintf(char* __restrict, const char* __restrict _Nonnull, __va_list) __printflike(2, 0);
 char* tmpnam(char*) __attribute__((deprecated("tmpnam is unsafe, use mkstemp or tmpfile instead")));
 #if defined(__USE_BSD) || defined(__USE_GNU)
 #define P_tmpdir "/tmp/" /* deprecated */
@@ -243,20 +248,20 @@
 #define fwopen(cookie, fn) funopen(cookie, 0, fn, 0, 0)
 #endif /* __USE_BSD */
 
-extern char* __fgets_chk(char*, int, FILE*, size_t) __INTRODUCED_IN(17);
-extern char* __fgets_real(char*, int, FILE*) __RENAME(fgets);
+char* __fgets_chk(char*, int, FILE*, size_t) __INTRODUCED_IN(17);
+char* __fgets_real(char*, int, FILE*) __RENAME(fgets);
 __errordecl(__fgets_too_big_error, "fgets called with size bigger than buffer");
 __errordecl(__fgets_too_small_error, "fgets called with size less than zero");
 
-extern size_t __fread_chk(void* __restrict, size_t, size_t, FILE* __restrict, size_t)
+size_t __fread_chk(void* __restrict, size_t, size_t, FILE* __restrict, size_t)
   __INTRODUCED_IN(24);
-extern size_t __fread_real(void * __restrict, size_t, size_t, FILE * __restrict) __RENAME(fread);
+size_t __fread_real(void * __restrict, size_t, size_t, FILE * __restrict) __RENAME(fread);
 __errordecl(__fread_too_big_error, "fread called with size * count bigger than buffer");
 __errordecl(__fread_overflow, "fread called with overflowing size * count");
 
-extern size_t __fwrite_chk(const void* __restrict, size_t, size_t, FILE* __restrict, size_t)
+size_t __fwrite_chk(const void* __restrict, size_t, size_t, FILE* __restrict, size_t)
   __INTRODUCED_IN(24);
-extern size_t __fwrite_real(const void * __restrict, size_t, size_t, FILE * __restrict) __RENAME(fwrite);
+size_t __fwrite_real(const void * __restrict, size_t, size_t, FILE * __restrict) __RENAME(fwrite);
 __errordecl(__fwrite_too_big_error, "fwrite called with size * count bigger than buffer");
 __errordecl(__fwrite_overflow, "fwrite called with overflowing size * count");
 
@@ -384,6 +389,10 @@
 
 #endif /* defined(__BIONIC_FORTIFY) */
 
+#if defined(__clang__)
+#pragma clang diagnostic pop
+#endif
+
 __END_DECLS
 
 #endif /* _STDIO_H_ */
diff --git a/libc/include/string.h b/libc/include/string.h
index b3ea9d6..c5bcd22 100644
--- a/libc/include/string.h
+++ b/libc/include/string.h
@@ -37,117 +37,119 @@
 
 __BEGIN_DECLS
 
+#if defined(__clang__)
+#pragma clang diagnostic push
+#pragma clang diagnostic ignored "-Wnullability-completeness"
+#endif
+
 #if defined(__USE_BSD)
 #include <strings.h>
 #endif
 
-extern void*  memccpy(void* __restrict, const void* __restrict, int, size_t);
-extern void*  memchr(const void *, int, size_t) __purefunc;
-extern void*  memrchr(const void *, int, size_t) __purefunc;
-extern int    memcmp(const void *, const void *, size_t) __purefunc;
-extern void*  memcpy(void* __restrict, const void* __restrict, size_t);
+void* memccpy(void* _Nonnull __restrict, const void* _Nonnull __restrict, int, size_t);
+void* memchr(const void* _Nonnull, int, size_t) __purefunc;
+void* memrchr(const void* _Nonnull, int, size_t) __purefunc;
+int memcmp(const void* _Nonnull, const void* _Nonnull, size_t) __purefunc;
+void* memcpy(void* _Nonnull __restrict, const void* _Nonnull __restrict, size_t);
 #if defined(__USE_GNU)
-extern void* mempcpy(void* __restrict, const void* __restrict, size_t) __INTRODUCED_IN(23);
+void* mempcpy(void* _Nonnull __restrict, const void* _Nonnull __restrict, size_t) __INTRODUCED_IN(23);
 #endif
-extern void*  memmove(void *, const void *, size_t);
-extern void*  memset(void *, int, size_t);
-extern void*  memmem(const void *, size_t, const void *, size_t) __purefunc;
+void* memmove(void* _Nonnull, const void* _Nonnull, size_t);
+void* memset(void* _Nonnull, int, size_t);
+void* memmem(const void* _Nonnull, size_t, const void* _Nonnull, size_t) __purefunc;
 
-extern char*  strchr(const char *, int) __purefunc;
-extern char* __strchr_chk(const char*, int, size_t) __INTRODUCED_IN(18);
+char* strchr(const char* _Nonnull, int) __purefunc;
+char* __strchr_chk(const char* _Nonnull, int, size_t) __INTRODUCED_IN(18);
 #if defined(__USE_GNU)
 #if defined(__cplusplus)
-extern "C++" char* strchrnul(char*, int) __RENAME(strchrnul) __purefunc;
-extern "C++" const char* strchrnul(const char*, int) __RENAME(strchrnul) __purefunc;
+extern "C++" char* strchrnul(char* _Nonnull, int) __RENAME(strchrnul) __purefunc;
+extern "C++" const char* strchrnul(const char* _Nonnull, int) __RENAME(strchrnul) __purefunc;
 #else
-char* strchrnul(const char*, int) __purefunc __INTRODUCED_IN(24);
+char* strchrnul(const char* _Nonnull, int) __purefunc __INTRODUCED_IN(24);
 #endif
 #endif
 
-extern char*  strrchr(const char *, int) __purefunc;
-extern char* __strrchr_chk(const char*, int, size_t) __INTRODUCED_IN(18);
+char* strrchr(const char* _Nonnull, int) __purefunc;
+char* __strrchr_chk(const char* _Nonnull, int, size_t) __INTRODUCED_IN(18);
 
-extern size_t strlen(const char *) __purefunc;
-extern size_t __strlen_chk(const char*, size_t) __INTRODUCED_IN(17);
-extern int    strcmp(const char *, const char *) __purefunc;
-extern char* stpcpy(char* __restrict, const char* __restrict) __INTRODUCED_IN(21);
-extern char*  strcpy(char* __restrict, const char* __restrict);
-extern char*  strcat(char* __restrict, const char* __restrict);
+size_t strlen(const char* _Nonnull) __purefunc;
+size_t __strlen_chk(const char* _Nonnull, size_t) __INTRODUCED_IN(17);
+int strcmp(const char* _Nonnull, const char* _Nonnull) __purefunc;
+char* stpcpy(char* _Nonnull __restrict, const char* _Nonnull__restrict) __INTRODUCED_IN(21);
+char* strcpy(char* _Nonnull __restrict, const char* _Nonnull __restrict);
+char* strcat(char* _Nonnull __restrict, const char* _Nonnull __restrict);
 
-extern char*  strdup(const char *);
+char* strdup(const char* _Nonnull);
 
-extern char*  strstr(const char *, const char *) __purefunc;
-extern char*  strcasestr(const char *haystack, const char *needle) __purefunc;
-extern char*  strtok(char* __restrict, const char* __restrict);
-extern char*  strtok_r(char* __restrict, const char* __restrict, char** __restrict);
+char* strstr(const char* _Nonnull, const char* _Nonnull) __purefunc;
+char* strcasestr(const char* _Nonnull, const char* _Nonnull) __purefunc;
+char* strtok(char* __restrict, const char* _Nonnull __restrict);
+char* strtok_r(char* __restrict, const char* _Nonnull __restrict, char** _Nonnull __restrict);
 
-extern char* strerror(int);
-extern char* strerror_l(int, locale_t) __INTRODUCED_IN(23);
+char* strerror(int);
+char* strerror_l(int, locale_t) __INTRODUCED_IN(23);
 #if defined(__USE_GNU)
-extern char* strerror_r(int, char*, size_t) __RENAME(__gnu_strerror_r) __INTRODUCED_IN(23);
+char* strerror_r(int, char*, size_t) __RENAME(__gnu_strerror_r) __INTRODUCED_IN(23);
 #else /* POSIX */
-extern int strerror_r(int, char*, size_t);
+int strerror_r(int, char*, size_t);
 #endif
 
-extern size_t strnlen(const char *, size_t) __purefunc;
-extern char*  strncat(char* __restrict, const char* __restrict, size_t);
-extern char*  strndup(const char *, size_t);
-extern int    strncmp(const char *, const char *, size_t) __purefunc;
-extern char* stpncpy(char* __restrict, const char* __restrict, size_t) __INTRODUCED_IN(21);
-extern char*  strncpy(char* __restrict, const char* __restrict, size_t);
+size_t strnlen(const char* _Nonnull, size_t) __purefunc;
+char* strncat(char* _Nonnull __restrict, const char* _Nonnull __restrict, size_t);
+char* strndup(const char* _Nonnull, size_t);
+int strncmp(const char* _Nonnull, const char* _Nonnull, size_t) __purefunc;
+char* stpncpy(char* _Nonnull __restrict, const char* _Nonnull __restrict, size_t) __INTRODUCED_IN(21);
+char* strncpy(char* _Nonnull __restrict, const char* _Nonnull __restrict, size_t);
 
-extern size_t strlcat(char* __restrict, const char* __restrict, size_t);
-extern 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);
 
-extern size_t strcspn(const char *, const char *) __purefunc;
-extern char*  strpbrk(const char *, const char *) __purefunc;
-extern char*  strsep(char** __restrict, const char* __restrict);
-extern size_t strspn(const char *, const char *);
+size_t strcspn(const char* _Nonnull, const char* _Nonnull) __purefunc;
+char* strpbrk(const char* _Nonnull, const char* _Nonnull) __purefunc;
+char* strsep(char** _Nonnull __restrict, const char* _Nonnull __restrict);
+size_t strspn(const char* _Nonnull, const char* _Nonnull);
 
-extern char*  strsignal(int  sig);
+char* strsignal(int);
 
-extern int    strcoll(const char *, const char *) __purefunc;
-extern size_t strxfrm(char* __restrict, const char* __restrict, size_t);
+int strcoll(const char* _Nonnull, const char* _Nonnull) __purefunc;
+size_t strxfrm(char* __restrict, const char* _Nonnull __restrict, size_t);
 
-extern int strcoll_l(const char*, const char*, locale_t) __purefunc __INTRODUCED_IN(21);
-extern size_t strxfrm_l(char* __restrict, const char* __restrict, size_t, locale_t)
-  __INTRODUCED_IN(21);
+int strcoll_l(const char* _Nonnull, const char* _Nonnull, locale_t) __purefunc __INTRODUCED_IN(21);
+size_t strxfrm_l(char* __restrict, const char* _Nonnull __restrict, size_t, locale_t) __INTRODUCED_IN(21);
 
 #if defined(__USE_GNU) && !defined(basename)
 /*
  * glibc has a basename in <string.h> that's different to the POSIX one in <libgen.h>.
  * It doesn't modify its argument, and in C++ it's const-correct.
  */
-
 #if defined(__cplusplus)
 extern "C++" char* basename(char* _Nonnull) __RENAME(__gnu_basename);
 extern "C++" const char* basename(const char* _Nonnull) __RENAME(__gnu_basename);
 #else
-extern char* basename(const char* _Nonnull) __RENAME(__gnu_basename) __INTRODUCED_IN(23);
+char* basename(const char* _Nonnull) __RENAME(__gnu_basename) __INTRODUCED_IN(23);
 #endif
 #endif
 
-extern void* __memchr_chk(const void*, int, size_t, size_t) __INTRODUCED_IN(23);
+void* __memchr_chk(const void* _Nonnull, int, size_t, size_t) __INTRODUCED_IN(23);
 __errordecl(__memchr_buf_size_error, "memchr called with size bigger than buffer");
 
-extern void* __memrchr_chk(const void*, int, size_t, size_t) __INTRODUCED_IN(23);
+void* __memrchr_chk(const void* _Nonnull, int, size_t, size_t) __INTRODUCED_IN(23);
 __errordecl(__memrchr_buf_size_error, "memrchr called with size bigger than buffer");
-extern void* __memrchr_real(const void*, int, size_t) __RENAME(memrchr);
+void* __memrchr_real(const void* _Nonnull, int, size_t) __RENAME(memrchr);
 
-extern char* __stpncpy_chk2(char* __restrict, const char* __restrict, size_t, size_t, size_t)
+char* __stpncpy_chk2(char* _Nonnull __restrict, const char* _Nonnull __restrict, size_t, size_t, size_t)
   __INTRODUCED_IN(21);
-extern char* __strncpy_chk2(char* __restrict, const char* __restrict, size_t, size_t, size_t)
+char* __strncpy_chk2(char* _Nonnull __restrict, const char* _Nonnull __restrict, size_t, size_t, size_t)
   __INTRODUCED_IN(21);
-extern size_t __strlcpy_real(char* __restrict, const char* __restrict, size_t) __RENAME(strlcpy);
-extern size_t __strlcpy_chk(char*, const char*, size_t, size_t) __INTRODUCED_IN(17);
-extern size_t __strlcat_real(char* __restrict, const char* __restrict, size_t) __RENAME(strlcat);
-extern size_t __strlcat_chk(char* __restrict, const char* __restrict, size_t, size_t)
-  __INTRODUCED_IN(17);
+size_t __strlcpy_real(char* _Nonnull __restrict, const char* _Nonnull __restrict, size_t) __RENAME(strlcpy);
+size_t __strlcpy_chk(char* _Nonnull __restrict, const char* _Nonnull __restrict, size_t, size_t) __INTRODUCED_IN(17);
+size_t __strlcat_real(char* _Nonnull __restrict, const char* _Nonnull __restrict, size_t) __RENAME(strlcat);
+size_t __strlcat_chk(char* _Nonnull __restrict, const char* _Nonnull __restrict, size_t, size_t) __INTRODUCED_IN(17);
 
 #if defined(__BIONIC_FORTIFY)
 
 __BIONIC_FORTIFY_INLINE
-void* memchr(const void *s, int c, size_t n) {
+void* memchr(const void* s, int c, size_t n) {
     size_t bos = __bos(s);
 
 #if !defined(__clang__)
@@ -168,7 +170,7 @@
 }
 
 __BIONIC_FORTIFY_INLINE
-void* memrchr(const void *s, int c, size_t n) {
+void* memrchr(const void* s, int c, size_t n) {
     size_t bos = __bos(s);
 
 #if !defined(__clang__)
@@ -189,125 +191,125 @@
 }
 
 __BIONIC_FORTIFY_INLINE
-void* memcpy(void* __restrict dest, const void* __restrict src, size_t copy_amount) {
-    return __builtin___memcpy_chk(dest, src, copy_amount, __bos0(dest));
+void* memcpy(void* _Nonnull __restrict dst, const void* _Nonnull __restrict src, size_t copy_amount) {
+    return __builtin___memcpy_chk(dst, src, copy_amount, __bos0(dst));
 }
 
 __BIONIC_FORTIFY_INLINE
-void* memmove(void *dest, const void *src, size_t len) {
-    return __builtin___memmove_chk(dest, src, len, __bos0(dest));
+void* memmove(void* _Nonnull dst, const void* _Nonnull src, size_t len) {
+    return __builtin___memmove_chk(dst, src, len, __bos0(dst));
 }
 
 __BIONIC_FORTIFY_INLINE
-char* stpcpy(char* __restrict dest, const char* __restrict src) {
-    return __builtin___stpcpy_chk(dest, src, __bos(dest));
+char* stpcpy(char* _Nonnull __restrict dst, const char* _Nonnull __restrict src) {
+    return __builtin___stpcpy_chk(dst, src, __bos(dst));
 }
 
 __BIONIC_FORTIFY_INLINE
-char* strcpy(char* __restrict dest, const char* __restrict src) {
-    return __builtin___strcpy_chk(dest, src, __bos(dest));
+char* strcpy(char* _Nonnull __restrict dst, const char* _Nonnull __restrict src) {
+    return __builtin___strcpy_chk(dst, src, __bos(dst));
 }
 
 __BIONIC_FORTIFY_INLINE
-char* stpncpy(char* __restrict dest, const char* __restrict src, size_t n) {
-    size_t bos_dest = __bos(dest);
+char* stpncpy(char* _Nonnull __restrict dst, const char* _Nonnull __restrict src, size_t n) {
+    size_t bos_dst = __bos(dst);
     size_t bos_src = __bos(src);
 
     if (bos_src == __BIONIC_FORTIFY_UNKNOWN_SIZE) {
-        return __builtin___stpncpy_chk(dest, src, n, bos_dest);
+        return __builtin___stpncpy_chk(dst, src, n, bos_dst);
     }
 
     if (__builtin_constant_p(n) && (n <= bos_src)) {
-        return __builtin___stpncpy_chk(dest, src, n, bos_dest);
+        return __builtin___stpncpy_chk(dst, src, n, bos_dst);
     }
 
     size_t slen = __builtin_strlen(src);
     if (__builtin_constant_p(slen)) {
-        return __builtin___stpncpy_chk(dest, src, n, bos_dest);
+        return __builtin___stpncpy_chk(dst, src, n, bos_dst);
     }
 
-    return __stpncpy_chk2(dest, src, n, bos_dest, bos_src);
+    return __stpncpy_chk2(dst, src, n, bos_dst, bos_src);
 }
 
 __BIONIC_FORTIFY_INLINE
-char* strncpy(char* __restrict dest, const char* __restrict src, size_t n) {
-    size_t bos_dest = __bos(dest);
+char* strncpy(char* _Nonnull __restrict dst, const char* _Nonnull __restrict src, size_t n) {
+    size_t bos_dst = __bos(dst);
     size_t bos_src = __bos(src);
 
     if (bos_src == __BIONIC_FORTIFY_UNKNOWN_SIZE) {
-        return __builtin___strncpy_chk(dest, src, n, bos_dest);
+        return __builtin___strncpy_chk(dst, src, n, bos_dst);
     }
 
     if (__builtin_constant_p(n) && (n <= bos_src)) {
-        return __builtin___strncpy_chk(dest, src, n, bos_dest);
+        return __builtin___strncpy_chk(dst, src, n, bos_dst);
     }
 
     size_t slen = __builtin_strlen(src);
     if (__builtin_constant_p(slen)) {
-        return __builtin___strncpy_chk(dest, src, n, bos_dest);
+        return __builtin___strncpy_chk(dst, src, n, bos_dst);
     }
 
-    return __strncpy_chk2(dest, src, n, bos_dest, bos_src);
+    return __strncpy_chk2(dst, src, n, bos_dst, bos_src);
 }
 
 __BIONIC_FORTIFY_INLINE
-char* strcat(char* __restrict dest, const char* __restrict src) {
-    return __builtin___strcat_chk(dest, src, __bos(dest));
+char* strcat(char* _Nonnull __restrict dst, const char* _Nonnull __restrict src) {
+    return __builtin___strcat_chk(dst, src, __bos(dst));
 }
 
 __BIONIC_FORTIFY_INLINE
-char *strncat(char* __restrict dest, const char* __restrict src, size_t n) {
-    return __builtin___strncat_chk(dest, src, n, __bos(dest));
+char *strncat(char* _Nonnull __restrict dst, const char* _Nonnull __restrict src, size_t n) {
+    return __builtin___strncat_chk(dst, src, n, __bos(dst));
 }
 
 __BIONIC_FORTIFY_INLINE
-void* memset(void *s, int c, size_t n) {
+void* memset(void* _Nonnull s, int c, size_t n) {
     return __builtin___memset_chk(s, c, n, __bos0(s));
 }
 
 __BIONIC_FORTIFY_INLINE
-size_t strlcpy(char* __restrict dest, const char* __restrict src, size_t size) {
-    size_t bos = __bos(dest);
+size_t strlcpy(char* _Nonnull __restrict dst, const char* _Nonnull __restrict src, size_t size) {
+    size_t bos = __bos(dst);
 
 #if !defined(__clang__)
     // Compiler doesn't know destination size. Don't call __strlcpy_chk
     if (bos == __BIONIC_FORTIFY_UNKNOWN_SIZE) {
-        return __strlcpy_real(dest, src, size);
+        return __strlcpy_real(dst, src, size);
     }
 
     // Compiler can prove, at compile time, that the passed in size
     // is always <= the actual object size. Don't call __strlcpy_chk
     if (__builtin_constant_p(size) && (size <= bos)) {
-        return __strlcpy_real(dest, src, size);
+        return __strlcpy_real(dst, src, size);
     }
 #endif /* !defined(__clang__) */
 
-    return __strlcpy_chk(dest, src, size, bos);
+    return __strlcpy_chk(dst, src, size, bos);
 }
 
 
 __BIONIC_FORTIFY_INLINE
-size_t strlcat(char* __restrict dest, const char* __restrict src, size_t size) {
-    size_t bos = __bos(dest);
+size_t strlcat(char* _Nonnull __restrict dst, const char* _Nonnull __restrict src, size_t size) {
+    size_t bos = __bos(dst);
 
 #if !defined(__clang__)
     // Compiler doesn't know destination size. Don't call __strlcat_chk
     if (bos == __BIONIC_FORTIFY_UNKNOWN_SIZE) {
-        return __strlcat_real(dest, src, size);
+        return __strlcat_real(dst, src, size);
     }
 
     // Compiler can prove, at compile time, that the passed in size
     // is always <= the actual object size. Don't call __strlcat_chk
     if (__builtin_constant_p(size) && (size <= bos)) {
-        return __strlcat_real(dest, src, size);
+        return __strlcat_real(dst, src, size);
     }
 #endif /* !defined(__clang__) */
 
-    return __strlcat_chk(dest, src, size, bos);
+    return __strlcat_chk(dst, src, size, bos);
 }
 
 __BIONIC_FORTIFY_INLINE
-size_t strlen(const char *s) {
+size_t strlen(const char* _Nonnull s) {
     size_t bos = __bos(s);
 
 #if !defined(__clang__)
@@ -326,7 +328,7 @@
 }
 
 __BIONIC_FORTIFY_INLINE
-char* strchr(const char *s, int c) {
+char* strchr(const char* _Nonnull s, int c) {
     size_t bos = __bos(s);
 
 #if !defined(__clang__)
@@ -345,7 +347,7 @@
 }
 
 __BIONIC_FORTIFY_INLINE
-char* strrchr(const char *s, int c) {
+char* strrchr(const char* _Nonnull s, int c) {
     size_t bos = __bos(s);
 
 #if !defined(__clang__)
@@ -366,6 +368,10 @@
 
 #endif /* defined(__BIONIC_FORTIFY) */
 
+#if defined(__clang__)
+#pragma clang diagnostic pop
+#endif
+
 __END_DECLS
 
 #endif /* _STRING_H */
diff --git a/libc/include/sys/cdefs.h b/libc/include/sys/cdefs.h
index 89061b6..2688626 100644
--- a/libc/include/sys/cdefs.h
+++ b/libc/include/sys/cdefs.h
@@ -72,6 +72,12 @@
 #define	__static_cast(x,y)	(x)y
 #endif
 
+#if defined(__cplusplus)
+#define __BIONIC_CAST(_k,_t,_v) (_k<_t>(_v))
+#else
+#define __BIONIC_CAST(_k,_t,_v) ((_t) (_v))
+#endif
+
 /*
  * The __CONCAT macro is used to concatenate parts of symbol names, e.g.
  * with "#define OLD(foo) __CONCAT(old,foo)", OLD(foo) produces oldfoo.
@@ -88,9 +94,6 @@
 #define	__CONCAT(x,y)	x ## y
 #define	__STRING(x)	#x
 
-#define	__const		const		/* define reserved names to standard */
-#define	__signed	signed
-#define	__volatile	volatile
 #if defined(__cplusplus)
 #define	__inline	inline		/* convert to C++ keyword */
 #endif /* !__cplusplus */
@@ -102,17 +105,6 @@
 
 #endif	/* !(__STDC__ || __cplusplus) */
 
-/*
- * The following macro is used to remove const cast-away warnings
- * from gcc -Wcast-qual; it should be used with caution because it
- * can hide valid errors; in particular most valid uses are in
- * situations where the API requires it, not to cast away string
- * constants. We don't use *intptr_t on purpose here and we are
- * explicit about unsigned long so that we don't have additional
- * dependencies.
- */
-#define __UNCONST(a)	((void *)(unsigned long)(const void *)(a))
-
 #define __always_inline __attribute__((__always_inline__))
 #define __dead __attribute__((__noreturn__))
 #define __noreturn __attribute__((__noreturn__))
@@ -154,6 +146,7 @@
  */
 #if !(defined(__clang__) && __has_feature(nullability))
 #define _Nonnull
+#define _Nullable
 #endif
 
 #define __printflike(x, y) __attribute__((__format__(printf, x, y)))
@@ -198,8 +191,6 @@
 #define __errorattr(msg) __attribute__((__error__(msg)))
 #endif
 
-#define __warnattr(msg) __attribute__((__warning__(msg)))
-
 #define __errordecl(name, msg) extern void name(void) __errorattr(msg)
 
 /*
@@ -274,9 +265,13 @@
 #    define __bos(s) __builtin_object_size((s), 0)
 #  endif
 #  define __bos0(s) __builtin_object_size((s), 0)
-#  define __BIONIC_FORTIFY_INLINE extern __inline__ __always_inline __attribute__((gnu_inline)) __attribute__((__artificial__))
+#  if defined(__clang__)
+#    define __BIONIC_FORTIFY_INLINE extern __inline__ __always_inline __attribute__((gnu_inline))
+#  else
+#    define __BIONIC_FORTIFY_INLINE extern __inline__ __always_inline __attribute__((gnu_inline)) __attribute__((__artificial__))
+#  endif
 #endif
-#define __BIONIC_FORTIFY_UNKNOWN_SIZE ((size_t) -1)
+#define __BIONIC_FORTIFY_UNKNOWN_SIZE __BIONIC_CAST(static_cast, size_t, -1)
 
 /* Used to tag non-static symbols that are private and never exposed by the shared library. */
 #define __LIBC_HIDDEN__ __attribute__((visibility("hidden")))
diff --git a/libc/include/sys/mman.h b/libc/include/sys/mman.h
index 7a8aa89..934963f 100644
--- a/libc/include/sys/mman.h
+++ b/libc/include/sys/mman.h
@@ -38,7 +38,7 @@
 #define MAP_ANON  MAP_ANONYMOUS
 #endif
 
-#define MAP_FAILED ((void *)-1)
+#define MAP_FAILED __BIONIC_CAST(reinterpret_cast, void*, -1)
 
 #define MREMAP_MAYMOVE  1
 #define MREMAP_FIXED    2
@@ -50,26 +50,26 @@
 #define POSIX_MADV_DONTNEED   MADV_DONTNEED
 
 #if defined(__USE_FILE_OFFSET64)
-extern void* mmap(void*, size_t, int, int, int, off_t) __RENAME(mmap64) __INTRODUCED_IN(21);
+void* mmap(void*, size_t, int, int, int, off_t) __RENAME(mmap64) __INTRODUCED_IN(21);
 #else
-extern void* mmap(void*, size_t, int, int, int, off_t);
+void* mmap(void*, size_t, int, int, int, off_t);
 #endif
-extern void* mmap64(void*, size_t, int, int, int, off64_t) __INTRODUCED_IN(21);
+void* mmap64(void*, size_t, int, int, int, off64_t) __INTRODUCED_IN(21);
 
-extern int munmap(void*, size_t);
-extern int msync(const void*, size_t, int);
-extern int mprotect(const void*, size_t, int);
-extern void* mremap(void*, size_t, size_t, int, ...);
+int munmap(void*, size_t);
+int msync(const void*, size_t, int);
+int mprotect(const void*, size_t, int);
+void* mremap(void*, size_t, size_t, int, ...);
 
-extern int mlockall(int) __INTRODUCED_IN(17);
-extern int munlockall(void) __INTRODUCED_IN(17);
-extern int mlock(const void*, size_t);
-extern int munlock(const void*, size_t);
+int mlockall(int) __INTRODUCED_IN(17);
+int munlockall(void) __INTRODUCED_IN(17);
+int mlock(const void*, size_t);
+int munlock(const void*, size_t);
 
-extern int mincore(void*, size_t, unsigned char*);
+int mincore(void*, size_t, unsigned char*);
 
-extern int madvise(void*, size_t, int);
-extern int posix_madvise(void*, size_t, int) __INTRODUCED_IN(23);
+int madvise(void*, size_t, int);
+int posix_madvise(void*, size_t, int) __INTRODUCED_IN(23);
 
 __END_DECLS
 
diff --git a/libc/include/sys/select.h b/libc/include/sys/select.h
index 06c1c72..96d735e 100644
--- a/libc/include/sys/select.h
+++ b/libc/include/sys/select.h
@@ -46,7 +46,7 @@
 
 #define __FDELT(fd) ((fd) / NFDBITS)
 #define __FDMASK(fd) (1UL << ((fd) % NFDBITS))
-#define __FDS_BITS(set) (((fd_set*)(set))->fds_bits)
+#define __FDS_BITS(set) (__BIONIC_CAST(static_cast, fd_set*, set)->fds_bits)
 
 /* Inline loop so we don't have to declare memset. */
 #define FD_ZERO(set) \
diff --git a/libc/include/sys/xattr.h b/libc/include/sys/xattr.h
index 63605c5..7e437e9 100644
--- a/libc/include/sys/xattr.h
+++ b/libc/include/sys/xattr.h
@@ -25,36 +25,33 @@
  * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  * SUCH DAMAGE.
  */
+
 #ifndef _SYS_XATTR_H_
 #define _SYS_XATTR_H_
 
+#include <linux/xattr.h>
 #include <sys/types.h>
 
 __BEGIN_DECLS
 
-#define XATTR_CREATE 1
-#define XATTR_REPLACE 2
-
-extern int fsetxattr(int fd, const char* name, const void* value, size_t size, int flags)
+int fsetxattr(int fd, const char* name, const void* value, size_t size, int flags)
   __INTRODUCED_IN(16);
-extern int setxattr(const char* path, const char* name, const void* value, size_t size, int flags)
+int setxattr(const char* path, const char* name, const void* value, size_t size, int flags)
   __INTRODUCED_IN(16);
-extern int lsetxattr(const char* path, const char* name, const void* value, size_t size, int flags)
+int lsetxattr(const char* path, const char* name, const void* value, size_t size, int flags)
   __INTRODUCED_IN(16);
 
-extern ssize_t fgetxattr(int fd, const char* name, void* value, size_t size) __INTRODUCED_IN(16);
-extern ssize_t getxattr(const char* path, const char* name, void* value, size_t size)
-  __INTRODUCED_IN(16);
-extern ssize_t lgetxattr(const char* path, const char* name, void* value, size_t size)
-  __INTRODUCED_IN(16);
+ssize_t fgetxattr(int fd, const char* name, void* value, size_t size) __INTRODUCED_IN(16);
+ssize_t getxattr(const char* path, const char* name, void* value, size_t size) __INTRODUCED_IN(16);
+ssize_t lgetxattr(const char* path, const char* name, void* value, size_t size) __INTRODUCED_IN(16);
 
-extern ssize_t listxattr(const char* path, char* list, size_t size) __INTRODUCED_IN(16);
-extern ssize_t llistxattr(const char* path, char* list, size_t size) __INTRODUCED_IN(16);
-extern ssize_t flistxattr(int fd, char* list, size_t size) __INTRODUCED_IN(16);
+ssize_t listxattr(const char* path, char* list, size_t size) __INTRODUCED_IN(16);
+ssize_t llistxattr(const char* path, char* list, size_t size) __INTRODUCED_IN(16);
+ssize_t flistxattr(int fd, char* list, size_t size) __INTRODUCED_IN(16);
 
-extern int removexattr(const char* path, const char* name) __INTRODUCED_IN(16);
-extern int lremovexattr(const char* path, const char* name) __INTRODUCED_IN(16);
-extern int fremovexattr(int fd, const char* name) __INTRODUCED_IN(16);
+int removexattr(const char* path, const char* name) __INTRODUCED_IN(16);
+int lremovexattr(const char* path, const char* name) __INTRODUCED_IN(16);
+int fremovexattr(int fd, const char* name) __INTRODUCED_IN(16);
 
 __END_DECLS
 
diff --git a/libc/include/syslog.h b/libc/include/syslog.h
index d51c9f2..ee288e5 100644
--- a/libc/include/syslog.h
+++ b/libc/include/syslog.h
@@ -86,7 +86,7 @@
 #define LOG_PERROR 0x20
 
 void closelog(void);
-void openlog(const char*, int, int);
+void openlog(const char* _Nullable, int, int);
 int setlogmask(int);
 void syslog(int, const char* _Nonnull, ...) __printflike(2, 3);
 void vsyslog(int, const char* _Nonnull, va_list) __printflike(2, 0);
diff --git a/libc/upstream-netbsd/android/include/netbsd-compat.h b/libc/upstream-netbsd/android/include/netbsd-compat.h
index 665d65e..cc0f71f 100644
--- a/libc/upstream-netbsd/android/include/netbsd-compat.h
+++ b/libc/upstream-netbsd/android/include/netbsd-compat.h
@@ -25,6 +25,17 @@
 // that they don't actually test or ship with this.
 #define _DIAGASSERT(e) /* nothing */
 
+/*
+ * The following macro is used to remove const cast-away warnings
+ * from gcc -Wcast-qual; it should be used with caution because it
+ * can hide valid errors; in particular most valid uses are in
+ * situations where the API requires it, not to cast away string
+ * constants. We don't use *intptr_t on purpose here and we are
+ * explicit about unsigned long so that we don't have additional
+ * dependencies.
+ */
+#define __UNCONST(a)    ((void *)(unsigned long)(const void *)(a))
+
 // TODO: we don't yet have thread-safe environment variables.
 #define __readlockenv() 0
 #define __unlockenv() 0