diff --git a/libc/Android.bp b/libc/Android.bp
index b86313c..1e65fea 100644
--- a/libc/Android.bp
+++ b/libc/Android.bp
@@ -2307,6 +2307,7 @@
     },
     whole_static_libs: [
         "libarm-optimized-routines-mem",
+        "libc_netbsd",
     ],
     system_shared_libs: [],
     nocrt: true,
diff --git a/libc/include/err.h b/libc/include/err.h
index e91dac9..af44514 100644
--- a/libc/include/err.h
+++ b/libc/include/err.h
@@ -50,7 +50,7 @@
  *
  * New code should consider error() in `<error.h>`.
  */
-__noreturn void err(int __status, const char* __fmt, ...) __printflike(2, 3);
+__noreturn void err(int __status, const char* _Nullable __fmt, ...) __printflike(2, 3);
 
 /**
  * [verr(3)](http://man7.org/linux/man-pages/man3/verr.3.html) outputs the program name,
@@ -60,7 +60,7 @@
  *
  * New code should consider error() in `<error.h>`.
  */
-__noreturn void verr(int __status, const char* __fmt, va_list __args) __printflike(2, 0);
+__noreturn void verr(int __status, const char* _Nullable __fmt, va_list __args) __printflike(2, 0);
 
 /**
  * [errx(3)](http://man7.org/linux/man-pages/man3/errx.3.html) outputs the program name, and
@@ -70,7 +70,7 @@
  *
  * New code should consider error() in `<error.h>`.
  */
-__noreturn void errx(int __status, const char* __fmt, ...) __printflike(2, 3);
+__noreturn void errx(int __status, const char* _Nullable __fmt, ...) __printflike(2, 3);
 
 /**
  * [verrx(3)](http://man7.org/linux/man-pages/man3/err.3.html) outputs the program name, and
@@ -80,7 +80,7 @@
  *
  * New code should consider error() in `<error.h>`.
  */
-__noreturn void verrx(int __status, const char* __fmt, va_list __args) __printflike(2, 0);
+__noreturn void verrx(int __status, const char* _Nullable __fmt, va_list __args) __printflike(2, 0);
 
 /**
  * [warn(3)](http://man7.org/linux/man-pages/man3/warn.3.html) outputs the program name,
@@ -88,7 +88,7 @@
  *
  * New code should consider error() in `<error.h>`.
  */
-void warn(const char* __fmt, ...) __printflike(1, 2);
+void warn(const char* _Nullable __fmt, ...) __printflike(1, 2);
 
 /**
  * [vwarn(3)](http://man7.org/linux/man-pages/man3/vwarn.3.html) outputs the program name,
@@ -96,7 +96,7 @@
  *
  * New code should consider error() in `<error.h>`.
  */
-void vwarn(const char* __fmt, va_list __args) __printflike(1, 0);
+void vwarn(const char* _Nullable __fmt, va_list __args) __printflike(1, 0);
 
 /**
  * [warnx(3)](http://man7.org/linux/man-pages/man3/warnx.3.html) outputs the program name, and
@@ -104,7 +104,7 @@
  *
  * New code should consider error() in `<error.h>`.
  */
-void warnx(const char* __fmt, ...) __printflike(1, 2);
+void warnx(const char* _Nullable __fmt, ...) __printflike(1, 2);
 
 /**
  * [vwarnx(3)](http://man7.org/linux/man-pages/man3/warn.3.html) outputs the program name, and
@@ -112,6 +112,6 @@
  *
  * New code should consider error() in `<error.h>`.
  */
-void vwarnx(const char* __fmt, va_list __args) __printflike(1, 0);
+void vwarnx(const char* _Nullable __fmt, va_list __args) __printflike(1, 0);
 
 __END_DECLS
diff --git a/libc/include/errno.h b/libc/include/errno.h
index ab56bb3..12ebdf7 100644
--- a/libc/include/errno.h
+++ b/libc/include/errno.h
@@ -49,7 +49,7 @@
  *
  * @private
  */
-int* __errno(void) __attribute_const__;
+int* _Nonnull __errno(void) __attribute_const__;
 
 /**
  * [errno(3)](http://man7.org/linux/man-pages/man3/errno.3.html) is the last error on the calling
diff --git a/libc/include/error.h b/libc/include/error.h
index 036a831..187ee17 100644
--- a/libc/include/error.h
+++ b/libc/include/error.h
@@ -44,7 +44,7 @@
  *
  * Available since API level 23.
  */
-extern void (*error_print_progname)(void) __INTRODUCED_IN(23);
+extern void (* _Nullable error_print_progname)(void) __INTRODUCED_IN(23);
 
 /**
  * [error_message_count(3)](http://man7.org/linux/man-pages/man3/error_message_count.3.html) is
@@ -70,7 +70,7 @@
  *
  * Available since API level 23.
  */
-void error(int __status, int __errno, const char* __fmt, ...) __printflike(3, 4) __INTRODUCED_IN(23);
+void error(int __status, int __errno, const char* _Nonnull __fmt, ...) __printflike(3, 4) __INTRODUCED_IN(23);
 
 /**
  * [error_at_line(3)](http://man7.org/linux/man-pages/man3/error_at_line.3.html) formats the given
@@ -80,6 +80,6 @@
  *
  * Available since API level 23.
  */
-void error_at_line(int __status, int __errno, const char* __filename, unsigned int __line_number, const char* __fmt, ...) __printflike(5, 6) __INTRODUCED_IN(23);
+void error_at_line(int __status, int __errno, const char* _Nonnull __filename, unsigned int __line_number, const char* _Nonnull __fmt, ...) __printflike(5, 6) __INTRODUCED_IN(23);
 
 __END_DECLS
diff --git a/libc/include/ftw.h b/libc/include/ftw.h
index a289643..c5fa4de 100644
--- a/libc/include/ftw.h
+++ b/libc/include/ftw.h
@@ -55,10 +55,10 @@
 };
 
 __BEGIN_DECLS
-int ftw(const char* __dir_path, int (*__callback)(const char*, const struct stat*, int), int __max_fd_count) __INTRODUCED_IN(17);
-int nftw(const char* __dir_path, int (*__callback)(const char*, const struct stat*, int, struct FTW*), int __max_fd_count, int __flags) __INTRODUCED_IN(17);
-int ftw64(const char* __dir_path, int (*__callback)(const char*, const struct stat64*, int), int __max_fd_count) __RENAME_STAT64(ftw, 17, 21);
-int nftw64(const char* __dir_path, int (*__callback)(const char*, const struct stat64*, int, struct FTW*), int __max_fd_count, int __flags) __RENAME_STAT64(nftw, 17, 21);
+int ftw(const char* _Nonnull __dir_path, int (* _Nonnull __callback)(const char* _Nonnull, const struct stat* _Nonnull, int), int __max_fd_count) __INTRODUCED_IN(17);
+int nftw(const char* _Nonnull __dir_path, int (* _Nonnull __callback)(const char* _Nonnull, const struct stat* _Nonnull, int, struct FTW* _Nonnull), int __max_fd_count, int __flags) __INTRODUCED_IN(17);
+int ftw64(const char* _Nonnull __dir_path, int (* _Nonnull __callback)(const char* _Nonnull, const struct stat64* _Nonnull, int), int __max_fd_count) __RENAME_STAT64(ftw, 17, 21);
+int nftw64(const char* _Nonnull __dir_path, int (* _Nonnull __callback)(const char* _Nonnull, const struct stat64* _Nonnull, int, struct FTW* _Nonnull), int __max_fd_count, int __flags) __RENAME_STAT64(nftw, 17, 21);
 __END_DECLS
 
 #endif
diff --git a/libc/include/iconv.h b/libc/include/iconv.h
index ec4bdea..7cf36dc 100644
--- a/libc/include/iconv.h
+++ b/libc/include/iconv.h
@@ -54,7 +54,7 @@
  *
  * Available since API level 28.
  */
-iconv_t iconv_open(const char* __src_encoding, const char* __dst_encoding) __INTRODUCED_IN(28);
+iconv_t _Nonnull iconv_open(const char* _Nonnull __src_encoding, const char* _Nonnull __dst_encoding) __INTRODUCED_IN(28);
 
 /**
  * [iconv(3)](http://man7.org/linux/man-pages/man3/iconv.3.html) converts characters from one
@@ -68,7 +68,7 @@
  *
  * Available since API level 28.
  */
-size_t iconv(iconv_t __converter, char** __src_buf, size_t* __src_bytes_left, char** __dst_buf, size_t* __dst_bytes_left) __INTRODUCED_IN(28);
+size_t iconv(iconv_t _Nonnull __converter, char* _Nullable * _Nullable __src_buf, size_t* __BIONIC_COMPLICATED_NULLNESS __src_bytes_left, char* _Nullable * _Nullable __dst_buf, size_t* __BIONIC_COMPLICATED_NULLNESS __dst_bytes_left) __INTRODUCED_IN(28);
 
 /**
  * [iconv_close(3)](http://man7.org/linux/man-pages/man3/iconv_close.3.html) deallocates a converter
@@ -78,6 +78,6 @@
  *
  * Available since API level 28.
  */
-int iconv_close(iconv_t __converter) __INTRODUCED_IN(28);
+int iconv_close(iconv_t _Nonnull __converter) __INTRODUCED_IN(28);
 
 __END_DECLS