diff --git a/libc/arch-riscv64/bionic/__bionic_clone.S b/libc/arch-riscv64/bionic/__bionic_clone.S
index d535095..2827857 100644
--- a/libc/arch-riscv64/bionic/__bionic_clone.S
+++ b/libc/arch-riscv64/bionic/__bionic_clone.S
@@ -51,7 +51,7 @@
 .L_bc_failure:
   # Set errno if something went wrong.
   neg a0, a0
-  j __set_errno_internal
+  tail __set_errno_internal
 
 .L_bc_child:
   # We're in the child now. Set the end of the frame record chain.
@@ -62,5 +62,5 @@
   ld a0, 0(sp)
   ld a1, 8(sp)
   addi sp, sp, 16
-  j __start_thread
+  tail __start_thread
 END(__bionic_clone)
diff --git a/libc/arch-riscv64/bionic/syscall.S b/libc/arch-riscv64/bionic/syscall.S
index 7b9d3ca..1a6e60a 100644
--- a/libc/arch-riscv64/bionic/syscall.S
+++ b/libc/arch-riscv64/bionic/syscall.S
@@ -49,5 +49,5 @@
   ret
 1:
   neg a0, a0
-  j __set_errno_internal
+  tail __set_errno_internal
 END(syscall)
diff --git a/libc/arch-riscv64/bionic/vfork.S b/libc/arch-riscv64/bionic/vfork.S
index 0eff9e9..29ab405 100644
--- a/libc/arch-riscv64/bionic/vfork.S
+++ b/libc/arch-riscv64/bionic/vfork.S
@@ -62,5 +62,5 @@
 
 .L_failure:
   neg     a0, a0
-  j       __set_errno_internal
+  tail    __set_errno_internal
 END(vfork)
diff --git a/libc/include/assert.h b/libc/include/assert.h
index 79e7b86..8db970b 100644
--- a/libc/include/assert.h
+++ b/libc/include/assert.h
@@ -75,12 +75,12 @@
  * __assert() is called by assert() on failure. Most users want assert()
  * instead, but this can be useful for reporting other failures.
  */
-void __assert(const char* __file, int __line, const char* __msg) __noreturn;
+void __assert(const char* _Nonnull __file, int __line, const char* _Nonnull __msg) __noreturn;
 
 /**
  * __assert2() is called by assert() on failure. Most users want assert()
  * instead, but this can be useful for reporting other failures.
  */
-void __assert2(const char* __file, int __line, const char* __function, const char* __msg) __noreturn;
+void __assert2(const char* _Nonnull __file, int __line, const char* _Nonnull __function, const char* _Nonnull __msg) __noreturn;
 
 __END_DECLS
diff --git a/libc/include/grp.h b/libc/include/grp.h
index 9d67adf..2451db5 100644
--- a/libc/include/grp.h
+++ b/libc/include/grp.h
@@ -39,26 +39,26 @@
 #include <sys/types.h>
 
 struct group {
-  char* gr_name; /* group name */
-  char* gr_passwd; /* group password */
+  char* _Nullable gr_name; /* group name */
+  char* _Nullable gr_passwd; /* group password */
   gid_t gr_gid; /* group id */
-  char** gr_mem; /* group members */
+  char* _Nullable * _Nullable gr_mem; /* group members */
 };
 
 __BEGIN_DECLS
 
-struct group* getgrgid(gid_t __gid);
-struct group* getgrnam(const char* __name);
+struct group* _Nullable getgrgid(gid_t __gid);
+struct group* _Nullable getgrnam(const char* _Nonnull __name);
 
 /* Note: Android has thousands and thousands of ids to iterate through. */
-struct group* getgrent(void) __INTRODUCED_IN(26);
+struct group* _Nullable getgrent(void) __INTRODUCED_IN(26);
 
 void setgrent(void) __INTRODUCED_IN(26);
 void endgrent(void) __INTRODUCED_IN(26);
-int getgrgid_r(gid_t __gid, struct group* __group, char* __buf, size_t __n, struct group** __result) __INTRODUCED_IN(24);
-int getgrnam_r(const char* __name, struct group* __group, char* __buf, size_t __n, struct group** __result) __INTRODUCED_IN(24);
-int getgrouplist(const char* __user, gid_t __group, gid_t* __groups, int* __group_count);
-int initgroups(const char* __user, gid_t __group);
+int getgrgid_r(gid_t __gid, struct group* __BIONIC_COMPLICATED_NULLNESS __group, char* _Nonnull __buf, size_t __n, struct group* _Nullable * _Nonnull __result) __INTRODUCED_IN(24);
+int getgrnam_r(const char* _Nonnull __name, struct group* __BIONIC_COMPLICATED_NULLNESS __group, char* _Nonnull __buf, size_t __n, struct group* _Nullable *_Nonnull __result) __INTRODUCED_IN(24);
+int getgrouplist(const char* _Nonnull __user, gid_t __group, gid_t* __BIONIC_COMPLICATED_NULLNESS __groups, int* _Nonnull __group_count);
+int initgroups(const char* _Nonnull __user, gid_t __group);
 
 __END_DECLS
 
diff --git a/libc/include/inttypes.h b/libc/include/inttypes.h
index f8b7f7d..76aee38 100644
--- a/libc/include/inttypes.h
+++ b/libc/include/inttypes.h
@@ -85,6 +85,42 @@
 #define	PRIiPTR			__PRI_PTR_prefix"i"		/* intptr_t */
 
 /* fprintf macros for unsigned integers */
+#define	PRIb8			"b"		/* int8_t */
+#define	PRIb16			"b"		/* int16_t */
+#define	PRIb32			"b"		/* int32_t */
+#define	PRIb64			__PRI_64_prefix"b"		/* int64_t */
+
+#define	PRIbLEAST8		"b"		/* int_least8_t */
+#define	PRIbLEAST16		"b"		/* int_least16_t */
+#define	PRIbLEAST32		"b"		/* int_least32_t */
+#define	PRIbLEAST64		__PRI_64_prefix"b"		/* int_least64_t */
+
+#define	PRIbFAST8		"b"		/* int_fast8_t */
+#define	PRIbFAST16		__PRI_FAST_prefix"b"	/* int_fast16_t */
+#define	PRIbFAST32		__PRI_FAST_prefix"b"	/* int_fast32_t */
+#define	PRIbFAST64		__PRI_64_prefix"b"		/* int_fast64_t */
+
+#define	PRIbMAX			"jb"		/* intmax_t */
+#define	PRIbPTR			__PRI_PTR_prefix"b"		/* intptr_t */
+
+#define	PRIB8			"B"		/* int8_t */
+#define	PRIB16			"B"		/* int16_t */
+#define	PRIB32			"B"		/* int32_t */
+#define	PRIB64			__PRI_64_prefix"B"		/* int64_t */
+
+#define	PRIBLEAST8		"B"		/* int_least8_t */
+#define	PRIBLEAST16		"B"		/* int_least16_t */
+#define	PRIBLEAST32		"B"		/* int_least32_t */
+#define	PRIBLEAST64		__PRI_64_prefix"B"		/* int_least64_t */
+
+#define	PRIBFAST8		"B"		/* int_fast8_t */
+#define	PRIBFAST16		__PRI_FAST_prefix"B"	/* int_fast16_t */
+#define	PRIBFAST32		__PRI_FAST_prefix"B"	/* int_fast32_t */
+#define	PRIBFAST64		__PRI_64_prefix"B"		/* int_fast64_t */
+
+#define	PRIBMAX			"jB"		/* intmax_t */
+#define	PRIBPTR			__PRI_PTR_prefix"B"		/* intptr_t */
+
 #define	PRIo8			"o"		/* int8_t */
 #define	PRIo16			"o"		/* int16_t */
 #define	PRIo32			"o"		/* int32_t */
@@ -195,6 +231,42 @@
 #define	SCNiPTR			__PRI_PTR_prefix"i"		/* intptr_t */
 
 /* fscanf macros for unsigned integers */
+#define	SCNb8			"hhb"		/* uint8_t */
+#define	SCNb16			"hb"		/* uint16_t */
+#define	SCNb32			"b"		/* uint32_t */
+#define	SCNb64			__PRI_64_prefix"b"		/* uint64_t */
+
+#define	SCNbLEAST8		"hhb"		/* uint_least8_t */
+#define	SCNbLEAST16		"hb"		/* uint_least16_t */
+#define	SCNbLEAST32		"b"		/* uint_least32_t */
+#define	SCNbLEAST64		__PRI_64_prefix"b"		/* uint_least64_t */
+
+#define	SCNbFAST8		"hhb"		/* uint_fast8_t */
+#define	SCNbFAST16		__PRI_FAST_prefix"b"	/* uint_fast16_t */
+#define	SCNbFAST32		__PRI_FAST_prefix"b"	/* uint_fast32_t */
+#define	SCNbFAST64		__PRI_64_prefix"b"		/* uint_fast64_t */
+
+#define	SCNbMAX			"jb"		/* uintmax_t */
+#define	SCNbPTR			__PRI_PTR_prefix"b"		/* uintptr_t */
+
+#define	SCNB8			"hhB"		/* uint8_t */
+#define	SCNB16			"hB"		/* uint16_t */
+#define	SCNB32			"B"		/* uint32_t */
+#define	SCNB64			__PRI_64_prefix"B"		/* uint64_t */
+
+#define	SCNBLEAST8		"hhB"		/* uint_least8_t */
+#define	SCNBLEAST16		"hB"		/* uint_least16_t */
+#define	SCNBLEAST32		"B"		/* uint_least32_t */
+#define	SCNBLEAST64		__PRI_64_prefix"B"		/* uint_least64_t */
+
+#define	SCNBFAST8		"hhB"		/* uint_fast8_t */
+#define	SCNBFAST16		__PRI_FAST_prefix"B"	/* uint_fast16_t */
+#define	SCNBFAST32		__PRI_FAST_prefix"B"	/* uint_fast32_t */
+#define	SCNBFAST64		__PRI_64_prefix"B"		/* uint_fast64_t */
+
+#define	SCNBMAX			"jB"		/* uintmax_t */
+#define	SCNBPTR			__PRI_PTR_prefix"B"		/* uintptr_t */
+
 #define	SCNo8			"hho"		/* uint8_t */
 #define	SCNo16			"ho"		/* uint16_t */
 #define	SCNo32			"o"		/* uint32_t */
diff --git a/libc/include/stdio.h b/libc/include/stdio.h
index f4b2911..e748faa 100644
--- a/libc/include/stdio.h
+++ b/libc/include/stdio.h
@@ -59,9 +59,9 @@
 typedef struct __sFILE FILE;
 
 #if __ANDROID_API__ >= 23
-extern FILE* stdin __INTRODUCED_IN(23);
-extern FILE* stdout __INTRODUCED_IN(23);
-extern FILE* stderr __INTRODUCED_IN(23);
+extern FILE* _Nonnull stdin __INTRODUCED_IN(23);
+extern FILE* _Nonnull stdout __INTRODUCED_IN(23);
+extern FILE* _Nonnull stderr __INTRODUCED_IN(23);
 
 /* C99 and earlier plus current C++ standards say these must be macros. */
 #define stdin stdin
@@ -103,54 +103,54 @@
 #define L_tmpnam 4096
 #define TMP_MAX 308915776
 
-void clearerr(FILE* __fp);
-int fclose(FILE* __fp);
-int feof(FILE* __fp);
-int ferror(FILE* __fp);
-int fflush(FILE* __fp);
-int fgetc(FILE* __fp);
-char* fgets(char* __buf, int __size, FILE* __fp);
-int fprintf(FILE* __fp , const char* __fmt, ...) __printflike(2, 3);
-int fputc(int __ch, FILE* __fp);
-int fputs(const char* __s, FILE* __fp);
-size_t fread(void* __buf, size_t __size, size_t __count, FILE* __fp);
-int fscanf(FILE* __fp, const char* __fmt, ...) __scanflike(2, 3);
-size_t fwrite(const void* __buf, size_t __size, size_t __count, FILE* __fp);
-int getc(FILE* __fp);
+void clearerr(FILE* _Nonnull __fp);
+int fclose(FILE* _Nonnull __fp);
+int feof(FILE* _Nonnull __fp);
+int ferror(FILE* _Nonnull __fp);
+int fflush(FILE* _Nullable __fp);
+int fgetc(FILE* _Nonnull __fp);
+char* _Nullable fgets(char* _Nonnull __buf, int __size, FILE* _Nonnull __fp);
+int fprintf(FILE* _Nonnull __fp , const char* _Nonnull __fmt, ...) __printflike(2, 3);
+int fputc(int __ch, FILE* _Nonnull __fp);
+int fputs(const char* _Nonnull __s, FILE* _Nonnull __fp);
+size_t fread(void* _Nonnull __buf, size_t __size, size_t __count, FILE* _Nonnull __fp);
+int fscanf(FILE* _Nonnull __fp, const char* _Nonnull __fmt, ...) __scanflike(2, 3);
+size_t fwrite(const void* _Nonnull __buf, size_t __size, size_t __count, FILE* _Nonnull __fp);
+int getc(FILE* _Nonnull __fp);
 int getchar(void);
-ssize_t getdelim(char** __line_ptr, size_t* __line_length_ptr, int __delimiter, FILE* __fp) __INTRODUCED_IN(18);
-ssize_t getline(char** __line_ptr, size_t* __line_length_ptr, FILE* __fp) __INTRODUCED_IN(18);
+ssize_t getdelim(char* _Nullable * _Nonnull __line_ptr, size_t* _Nonnull __line_length_ptr, int __delimiter, FILE* _Nonnull __fp) __INTRODUCED_IN(18);
+ssize_t getline(char* _Nullable * _Nonnull __line_ptr, size_t* _Nonnull __line_length_ptr, FILE* _Nonnull __fp) __INTRODUCED_IN(18);
 
-void perror(const char* __msg);
-int printf(const char* __fmt, ...) __printflike(1, 2);
-int putc(int __ch, FILE* __fp);
+void perror(const char* _Nullable __msg);
+int printf(const char* _Nonnull __fmt, ...) __printflike(1, 2);
+int putc(int __ch, FILE* _Nonnull __fp);
 int putchar(int __ch);
-int puts(const char* __s);
-int remove(const char* __path);
-void rewind(FILE* __fp);
-int scanf(const char* __fmt, ...) __scanflike(1, 2);
-void setbuf(FILE* __fp, char* __buf);
-int setvbuf(FILE* __fp, char* __buf, int __mode, size_t __size);
-int sscanf(const char* __s, const char* __fmt, ...) __scanflike(2, 3);
-int ungetc(int __ch, FILE* __fp);
-int vfprintf(FILE* __fp, const char* __fmt, va_list __args) __printflike(2, 0);
-int vprintf(const char* __fp, va_list __args) __printflike(1, 0);
+int puts(const char* _Nonnull __s);
+int remove(const char* _Nonnull __path);
+void rewind(FILE* _Nonnull __fp);
+int scanf(const char* _Nonnull __fmt, ...) __scanflike(1, 2);
+void setbuf(FILE* _Nonnull __fp, char* _Nullable __buf);
+int setvbuf(FILE* _Nonnull __fp, char* _Nullable __buf, int __mode, size_t __size);
+int sscanf(const char* _Nonnull __s, const char* _Nonnull __fmt, ...) __scanflike(2, 3);
+int ungetc(int __ch, FILE* _Nonnull __fp);
+int vfprintf(FILE* _Nonnull __fp, const char* _Nonnull __fmt, va_list __args) __printflike(2, 0);
+int vprintf(const char* _Nonnull __fp, va_list __args) __printflike(1, 0);
 
-int dprintf(int __fd, const char* __fmt, ...) __printflike(2, 3) __INTRODUCED_IN(21);
-int vdprintf(int __fd, const char* __fmt, va_list __args) __printflike(2, 0) __INTRODUCED_IN(21);
+int dprintf(int __fd, const char* _Nonnull __fmt, ...) __printflike(2, 3) __INTRODUCED_IN(21);
+int vdprintf(int __fd, const char* _Nonnull __fmt, va_list __args) __printflike(2, 0) __INTRODUCED_IN(21);
 
 #if (defined(__STDC_VERSION__) && __STDC_VERSION__ < 201112L) || \
     (defined(__cplusplus) && __cplusplus <= 201103L)
-char* gets(char* __buf) __attribute__((deprecated("gets is unsafe, use fgets instead")));
+char* _Nullable gets(char* _Nonnull __buf) __attribute__((deprecated("gets is unsafe, use fgets instead")));
 #endif
-int sprintf(char* __s, const char* __fmt, ...)
+int sprintf(char* _Nonnull __s, const char* _Nonnull __fmt, ...)
     __printflike(2, 3) __warnattr_strict("sprintf is often misused; please use snprintf");
-int vsprintf(char* __s, const char* __fmt, va_list __args)
+int vsprintf(char* _Nonnull __s, const char* _Nonnull __fmt, va_list __args)
     __printflike(2, 0) __warnattr_strict("vsprintf is often misused; please use vsnprintf");
-char* tmpnam(char* __s)
+char* _Nullable tmpnam(char* _Nullable __s)
     __warnattr("tmpnam is unsafe, use mkstemp or tmpfile instead");
 #define P_tmpdir "/tmp/" /* deprecated */
-char* tempnam(const char* __dir, const char* __prefix)
+char* _Nullable tempnam(const char* _Nullable __dir, const char* _Nullable __prefix)
     __warnattr("tempnam is unsafe, use mkstemp or tmpfile instead");
 
 /**
@@ -159,7 +159,7 @@
  *
  * Returns 0 on success, and returns -1 and sets `errno` on failure.
  */
-int rename(const char* __old_path, const char* __new_path);
+int rename(const char* _Nonnull __old_path, const char* _Nonnull __new_path);
 
 /**
  * [renameat(2)](http://man7.org/linux/man-pages/man2/renameat.2.html) changes
@@ -167,7 +167,7 @@
  *
  * Returns 0 on success, and returns -1 and sets `errno` on failure.
  */
-int renameat(int __old_dir_fd, const char* __old_path, int __new_dir_fd, const char* __new_path);
+int renameat(int __old_dir_fd, const char* _Nonnull __old_path, int __new_dir_fd, const char* _Nonnull __new_path);
 
 #if defined(__USE_GNU)
 
@@ -196,108 +196,111 @@
  *
  * Returns 0 on success, and returns -1 and sets `errno` on failure.
  */
-int renameat2(int __old_dir_fd, const char* __old_path, int __new_dir_fd, const char* __new_path, unsigned __flags) __INTRODUCED_IN(30);
+int renameat2(int __old_dir_fd, const char* _Nonnull __old_path, int __new_dir_fd, const char* _Nonnull __new_path, unsigned __flags) __INTRODUCED_IN(30);
 
 #endif
 
-int fseek(FILE* __fp, long __offset, int __whence);
-long ftell(FILE* __fp);
+int fseek(FILE* _Nonnull __fp, long __offset, int __whence);
+long ftell(FILE* _Nonnull __fp);
 
 /* See https://android.googlesource.com/platform/bionic/+/master/docs/32-bit-abi.md */
 #if defined(__USE_FILE_OFFSET64)
-int fgetpos(FILE* __fp, fpos_t* __pos) __RENAME(fgetpos64) __INTRODUCED_IN(24);
-int fsetpos(FILE* __fp, const fpos_t* __pos) __RENAME(fsetpos64) __INTRODUCED_IN(24);
-int fseeko(FILE* __fp, off_t __offset, int __whence) __RENAME(fseeko64) __INTRODUCED_IN(24);
-off_t ftello(FILE* __fp) __RENAME(ftello64) __INTRODUCED_IN(24);
+int fgetpos(FILE* _Nonnull __fp, fpos_t* _Nonnull __pos) __RENAME(fgetpos64) __INTRODUCED_IN(24);
+int fsetpos(FILE* _Nonnull __fp, const fpos_t* _Nonnull __pos) __RENAME(fsetpos64) __INTRODUCED_IN(24);
+int fseeko(FILE* _Nonnull __fp, off_t __offset, int __whence) __RENAME(fseeko64) __INTRODUCED_IN(24);
+off_t ftello(FILE* _Nonnull __fp) __RENAME(ftello64) __INTRODUCED_IN(24);
 #  if defined(__USE_BSD)
-FILE* funopen(const void* __cookie,
-              int (*__read_fn)(void*, char*, int),
-              int (*__write_fn)(void*, const char*, int),
-              fpos_t (*__seek_fn)(void*, fpos_t, int),
-              int (*__close_fn)(void*)) __RENAME(funopen64) __INTRODUCED_IN(24);
+/* If __read_fn and __write_fn are both nullptr, it will cause EINVAL */
+FILE* _Nullable funopen(const void* _Nullable __cookie,
+              int (* __BIONIC_COMPLICATED_NULLNESS __read_fn)(void* _Nonnull, char* _Nonnull, int),
+              int (* __BIONIC_COMPLICATED_NULLNESS __write_fn)(void* _Nonnull, const char* _Nonnull, int),
+              fpos_t (* _Nullable __seek_fn)(void* _Nonnull, fpos_t, int),
+              int (* _Nullable __close_fn)(void* _Nonnull)) __RENAME(funopen64) __INTRODUCED_IN(24);
 #  endif
 #else
-int fgetpos(FILE* __fp, fpos_t* __pos);
-int fsetpos(FILE* __fp, const fpos_t* __pos);
-int fseeko(FILE* __fp, off_t __offset, int __whence);
-off_t ftello(FILE* __fp);
+int fgetpos(FILE* _Nonnull __fp, fpos_t* _Nonnull __pos);
+int fsetpos(FILE* _Nonnull __fp, const fpos_t* _Nonnull __pos);
+int fseeko(FILE* _Nonnull __fp, off_t __offset, int __whence);
+off_t ftello(FILE* _Nonnull __fp);
 #  if defined(__USE_BSD)
-FILE* funopen(const void* __cookie,
-              int (*__read_fn)(void*, char*, int),
-              int (*__write_fn)(void*, const char*, int),
-              fpos_t (*__seek_fn)(void*, fpos_t, int),
-              int (*__close_fn)(void*));
+/* If __read_fn and __write_fn are both nullptr, it will cause EINVAL */
+FILE* _Nullable funopen(const void* _Nullable __cookie,
+              int (* __BIONIC_COMPLICATED_NULLNESS __read_fn)(void* _Nonnull, char* _Nonnull, int),
+              int (* __BIONIC_COMPLICATED_NULLNESS __write_fn)(void* _Nonnull, const char* _Nonnull, int),
+              fpos_t (* _Nullable __seek_fn)(void* _Nonnull, fpos_t, int),
+              int (* _Nullable __close_fn)(void* _Nonnull));
 #  endif
 #endif
-int fgetpos64(FILE* __fp, fpos64_t* __pos) __INTRODUCED_IN(24);
-int fsetpos64(FILE* __fp, const fpos64_t* __pos) __INTRODUCED_IN(24);
-int fseeko64(FILE* __fp, off64_t __offset, int __whence) __INTRODUCED_IN(24);
-off64_t ftello64(FILE* __fp) __INTRODUCED_IN(24);
+int fgetpos64(FILE* _Nonnull __fp, fpos64_t* _Nonnull __pos) __INTRODUCED_IN(24);
+int fsetpos64(FILE* _Nonnull __fp, const fpos64_t* _Nonnull __pos) __INTRODUCED_IN(24);
+int fseeko64(FILE* _Nonnull __fp, off64_t __offset, int __whence) __INTRODUCED_IN(24);
+off64_t ftello64(FILE* _Nonnull __fp) __INTRODUCED_IN(24);
 #if defined(__USE_BSD)
-FILE* funopen64(const void* __cookie,
-                int (*__read_fn)(void*, char*, int),
-                int (*__write_fn)(void*, const char*, int),
-                fpos64_t (*__seek_fn)(void*, fpos64_t, int),
-                int (*__close_fn)(void*)) __INTRODUCED_IN(24);
+/* If __read_fn and __write_fn are both nullptr, it will cause EINVAL */
+FILE* _Nullable funopen64(const void* _Nullable __cookie,
+                int (* __BIONIC_COMPLICATED_NULLNESS __read_fn)(void* _Nonnull, char* _Nonnull, int),
+                int (* __BIONIC_COMPLICATED_NULLNESS __write_fn)(void* _Nonnull, const char* _Nonnull, int),
+                fpos64_t (* _Nullable __seek_fn)(void* _Nonnull, fpos64_t, int),
+                int (* _Nullable __close_fn)(void* _Nonnull)) __INTRODUCED_IN(24);
 #endif
 
-FILE* fopen(const char* __path, const char* __mode);
-FILE* fopen64(const char* __path, const char* __mode) __INTRODUCED_IN(24);
-FILE* freopen(const char* __path, const char* __mode, FILE* __fp);
-FILE* freopen64(const char* __path, const char* __mode, FILE* __fp) __INTRODUCED_IN(24);
-FILE* tmpfile(void);
-FILE* tmpfile64(void) __INTRODUCED_IN(24);
+FILE* _Nullable fopen(const char* _Nonnull __path, const char* _Nonnull __mode);
+FILE* _Nullable fopen64(const char* _Nonnull __path, const char* _Nonnull __mode) __INTRODUCED_IN(24);
+FILE* _Nullable freopen(const char* _Nullable __path, const char* _Nonnull __mode, FILE* _Nonnull __fp);
+FILE* _Nullable freopen64(const char* _Nullable __path, const char* _Nonnull __mode, FILE* _Nonnull __fp) __INTRODUCED_IN(24);
+FILE* _Nullable tmpfile(void);
+FILE* _Nullable tmpfile64(void) __INTRODUCED_IN(24);
 
-int snprintf(char* __buf, size_t __size, const char* __fmt, ...) __printflike(3, 4);
-int vfscanf(FILE* __fp, const char* __fmt, va_list __args) __scanflike(2, 0);
-int vscanf(const char* __fmt , va_list __args) __scanflike(1, 0);
-int vsnprintf(char* __buf, size_t __size, const char* __fmt, va_list __args) __printflike(3, 0);
-int vsscanf(const char* __s, const char* __fmt, va_list __args) __scanflike(2, 0);
+int snprintf(char* _Nullable __buf, size_t __size, const char* _Nonnull __fmt, ...) __printflike(3, 4);
+int vfscanf(FILE* _Nonnull __fp, const char* _Nonnull __fmt, va_list __args) __scanflike(2, 0);
+int vscanf(const char* _Nonnull __fmt , va_list __args) __scanflike(1, 0);
+int vsnprintf(char* _Nullable __buf, size_t __size, const char* _Nonnull __fmt, va_list __args) __printflike(3, 0);
+int vsscanf(const char* _Nonnull __s, const char* _Nonnull __fmt, va_list __args) __scanflike(2, 0);
 
 #define L_ctermid 1024 /* size for ctermid() */
-char* ctermid(char* __buf) __INTRODUCED_IN(26);
+char* _Nonnull ctermid(char* _Nullable __buf) __INTRODUCED_IN(26);
 
-FILE* fdopen(int __fd, const char* __mode);
-int fileno(FILE* __fp);
-int pclose(FILE* __fp);
-FILE* popen(const char* __command, const char* __mode);
-void flockfile(FILE* __fp);
-int ftrylockfile(FILE* __fp);
-void funlockfile(FILE* __fp);
-int getc_unlocked(FILE* __fp);
+FILE* _Nullable fdopen(int __fd, const char* _Nonnull __mode);
+int fileno(FILE* _Nonnull __fp);
+int pclose(FILE* _Nonnull __fp);
+FILE* _Nullable popen(const char* _Nonnull __command, const char* _Nonnull __mode);
+void flockfile(FILE* _Nonnull  __fp);
+int ftrylockfile(FILE* _Nonnull __fp);
+void funlockfile(FILE* _Nonnull __fp);
+int getc_unlocked(FILE* _Nonnull __fp);
 int getchar_unlocked(void);
-int putc_unlocked(int __ch, FILE* __fp);
+int putc_unlocked(int __ch, FILE* _Nonnull __fp);
 int putchar_unlocked(int __ch);
 
-FILE* fmemopen(void* __buf, size_t __size, const char* __mode) __INTRODUCED_IN(23);
-FILE* open_memstream(char** __ptr, size_t* __size_ptr) __INTRODUCED_IN(23);
+FILE* _Nullable fmemopen(void* _Nullable __buf, size_t __size, const char* _Nonnull __mode) __INTRODUCED_IN(23);
+FILE* _Nullable open_memstream(char* _Nonnull * _Nonnull __ptr, size_t* _Nonnull __size_ptr) __INTRODUCED_IN(23);
 
 #if defined(__USE_BSD) || defined(__BIONIC__) /* Historically bionic exposed these. */
-int  asprintf(char** __s_ptr, const char* __fmt, ...) __printflike(2, 3);
-char* fgetln(FILE* __fp, size_t* __length_ptr);
-int fpurge(FILE* __fp);
-void setbuffer(FILE* __fp, char* __buf, int __size);
-int setlinebuf(FILE* __fp);
-int vasprintf(char** __s_ptr, const char* __fmt, va_list __args) __printflike(2, 0);
-void clearerr_unlocked(FILE* __fp) __INTRODUCED_IN(23);
-int feof_unlocked(FILE* __fp) __INTRODUCED_IN(23);
-int ferror_unlocked(FILE* __fp) __INTRODUCED_IN(23);
-int fileno_unlocked(FILE* __fp) __INTRODUCED_IN(24);
+int  asprintf(char* _Nullable * _Nonnull __s_ptr, const char* _Nonnull __fmt, ...) __printflike(2, 3);
+char* _Nullable fgetln(FILE* _Nonnull __fp, size_t* _Nonnull __length_ptr);
+int fpurge(FILE* _Nonnull __fp);
+void setbuffer(FILE* _Nonnull __fp, char* _Nullable __buf, int __size);
+int setlinebuf(FILE* _Nonnull __fp);
+int vasprintf(char* _Nullable * _Nonnull __s_ptr, const char* _Nonnull __fmt, va_list __args) __printflike(2, 0);
+void clearerr_unlocked(FILE* _Nonnull __fp) __INTRODUCED_IN(23);
+int feof_unlocked(FILE* _Nonnull __fp) __INTRODUCED_IN(23);
+int ferror_unlocked(FILE* _Nonnull __fp) __INTRODUCED_IN(23);
+int fileno_unlocked(FILE* _Nonnull __fp) __INTRODUCED_IN(24);
 #define fropen(cookie, fn) funopen(cookie, fn, 0, 0, 0)
 #define fwopen(cookie, fn) funopen(cookie, 0, fn, 0, 0)
 #endif
 
 #if defined(__USE_BSD)
-int fflush_unlocked(FILE* __fp) __INTRODUCED_IN(28);
-int fgetc_unlocked(FILE* __fp) __INTRODUCED_IN(28);
-int fputc_unlocked(int __ch, FILE* __fp) __INTRODUCED_IN(28);
-size_t fread_unlocked(void* __buf, size_t __size, size_t __count, FILE* __fp) __INTRODUCED_IN(28);
-size_t fwrite_unlocked(const void* __buf, size_t __size, size_t __count, FILE* __fp) __INTRODUCED_IN(28);
+int fflush_unlocked(FILE* _Nullable __fp) __INTRODUCED_IN(28);
+int fgetc_unlocked(FILE* _Nonnull __fp) __INTRODUCED_IN(28);
+int fputc_unlocked(int __ch, FILE* _Nonnull __fp) __INTRODUCED_IN(28);
+size_t fread_unlocked(void* _Nonnull __buf, size_t __size, size_t __count, FILE* _Nonnull __fp) __INTRODUCED_IN(28);
+size_t fwrite_unlocked(const void* _Nonnull __buf, size_t __size, size_t __count, FILE* _Nonnull __fp) __INTRODUCED_IN(28);
 #endif
 
 #if defined(__USE_GNU)
-int fputs_unlocked(const char* __s, FILE* __fp) __INTRODUCED_IN(28);
-char* fgets_unlocked(char* __buf, int __size, FILE* __fp) __INTRODUCED_IN(28);
+int fputs_unlocked(const char* _Nonnull __s, FILE* _Nonnull __fp) __INTRODUCED_IN(28);
+char* _Nullable fgets_unlocked(char* _Nonnull __buf, int __size, FILE* _Nonnull __fp) __INTRODUCED_IN(28);
 #endif
 
 #if defined(__BIONIC_INCLUDE_FORTIFY_HEADERS)
diff --git a/libc/include/sys/ucontext.h b/libc/include/sys/ucontext.h
index 8e5873d..cefe177 100644
--- a/libc/include/sys/ucontext.h
+++ b/libc/include/sys/ucontext.h
@@ -316,6 +316,8 @@
 
 #define NGREG 32
 
+#if defined(__USE_GNU)
+
 #define REG_PC 0
 #define REG_RA 1
 #define REG_SP 2
@@ -323,6 +325,8 @@
 #define REG_S0 8
 #define REG_A0 10
 
+#endif // defined(__USE_GNU)
+
 typedef unsigned long __riscv_mc_gp_state[NGREG];
 
 typedef unsigned long greg_t;
diff --git a/libc/include/sys/utsname.h b/libc/include/sys/utsname.h
index 1fa3187..aa8c1a0 100644
--- a/libc/include/sys/utsname.h
+++ b/libc/include/sys/utsname.h
@@ -62,6 +62,6 @@
  *
  * Returns 0 on success, and returns -1 and sets `errno` on failure.
  */
-int uname(struct utsname* __buf);
+int uname(struct utsname* _Nonnull __buf);
 
 __END_DECLS
diff --git a/libc/tzcode/strptime.c b/libc/tzcode/strptime.c
index fe9e10f..d31a501 100644
--- a/libc/tzcode/strptime.c
+++ b/libc/tzcode/strptime.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: strptime.c,v 1.30 2019/05/12 12:49:52 schwarze Exp $ */
+/*	$OpenBSD: strptime.c,v 1.31 2023/03/02 16:21:51 millert Exp $ */
 /*	$NetBSD: strptime.c,v 1.12 1998/01/20 21:39:40 mycroft Exp $	*/
 /*-
  * Copyright (c) 1997, 1998, 2005, 2008 The NetBSD Foundation, Inc.
@@ -29,8 +29,10 @@
  */
 
 #include <ctype.h>
+#include <errno.h>
+#include <limits.h>
 #include <locale.h>
-#include <stdint.h>
+#include <stdlib.h>
 #include <string.h>
 #include <time.h>
 
@@ -43,6 +45,8 @@
 // Android: this code is not pointer-sign clean.
 #pragma clang diagnostic ignored "-Wpointer-sign"
 #pragma clang diagnostic ignored "-Wunused-function"
+// Android: clang thinks people don't know && has higher precedence than ||.
+#pragma clang diagnostic ignored "-Wlogical-op-parentheses"
 
 #define	_ctloc(x)		(_CurrentTimeLocale->x)
 
@@ -78,8 +82,8 @@
         { 31, 29, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 }
 };
 
-static	int _conv_num64(const unsigned char **, int64_t *, int64_t, int64_t);
 static	int _conv_num(const unsigned char **, int *, int, int);
+static	int epoch_to_tm(const unsigned char **, struct tm *);
 static	int leaps_thru_end_of(const int y);
 static	char *_strptime(const char *, const char *, struct tm *, int);
 static	const u_char *_find_string(const u_char *, int *, const char * const *,
@@ -351,27 +355,10 @@
 			if (!(_conv_num(&bp, &tm->tm_sec, 0, 60)))
 				return (NULL);
 			break;
-		case 's':	/* Seconds since epoch */
-			{
-				// Android change based on FreeBSD's implementation.
-				int saved_errno = errno;
-				errno = 0;
-				const unsigned char* old_bp = bp;
-				long n = strtol((const char*) bp, (char**) &bp, 10);
-				errno = saved_errno;
-				time_t t = n;
-				if (bp == old_bp || errno == ERANGE ||
-				    ((long) t) != n) return NULL;
-
-				if (localtime_r(&t, tm) == NULL) return NULL;
-
-				//int64_t i64;
-				//if (!(_conv_num64(&bp, &i64, 0, INT64_MAX)))
-				//	return (NULL);
-				//if (!gmtime_r(&i64, tm))
-				//	return (NULL);
-				fields = 0xffff;	 /* everything */
-			}
+		case 's':	/* Seconds since epoch. */
+			if (!(epoch_to_tm(&bp, tm)))
+				return (NULL);
+			fields = 0xffff;	 /* everything */
 			break;
 		case 'U':	/* The week of year, beginning on sunday. */
 		case 'W':	/* The week of year, beginning on monday. */
@@ -635,26 +622,27 @@
 }
 
 static int
-_conv_num64(const unsigned char **buf, int64_t *dest, int64_t llim, int64_t ulim)
+epoch_to_tm(const unsigned char **buf, struct tm *tm)
 {
-	int result = 0;
-	int64_t rulim = ulim;
+	int saved_errno = errno;
+	int ret = 0;
+	time_t secs;
+	char *ep;
 
-	if (**buf < '0' || **buf > '9')
-		return (0);
-
-	/* we use rulim to break out of the loop when we run out of digits */
-	do {
-		result *= 10;
-		result += *(*buf)++ - '0';
-		rulim /= 10;
-	} while ((result * 10 <= ulim) && rulim && **buf >= '0' && **buf <= '9');
-
-	if (result < llim || result > ulim)
-		return (0);
-
-	*dest = result;
-	return (1);
+	errno = 0;
+	secs = strtoll(*buf, &ep, 10);
+	if (*buf == (unsigned char *)ep)
+		goto done;
+	if (secs < 0 ||
+	    secs == LLONG_MAX && errno == ERANGE)
+		goto done;
+	if (localtime_r(&secs, tm) == NULL)
+		goto done;
+	ret = 1;
+done:
+	*buf = ep;
+	errno = saved_errno;
+	return (ret);
 }
 
 static const u_char *
diff --git a/libc/upstream-openbsd/lib/libc/gdtoa/gdtoaimp.h b/libc/upstream-openbsd/lib/libc/gdtoa/gdtoaimp.h
index 823f2a9..f853045 100644
--- a/libc/upstream-openbsd/lib/libc/gdtoa/gdtoaimp.h
+++ b/libc/upstream-openbsd/lib/libc/gdtoa/gdtoaimp.h
@@ -26,7 +26,7 @@
 
 ****************************************************************/
 
-/* This is a variation on dtoa.c that converts arbitary binary
+/* This is a variation on dtoa.c that converts arbitrary binary
    floating-point formats to and from decimal notation.  It uses
    double-precision arithmetic internally, so there are still
    various #ifdefs that adapt the calculations to the native
diff --git a/libc/upstream-openbsd/lib/libc/stdio/setvbuf.c b/libc/upstream-openbsd/lib/libc/stdio/setvbuf.c
index 9a08d13..74a1695 100644
--- a/libc/upstream-openbsd/lib/libc/stdio/setvbuf.c
+++ b/libc/upstream-openbsd/lib/libc/stdio/setvbuf.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: setvbuf.c,v 1.14 2016/09/21 04:38:56 guenther Exp $ */
+/*	$OpenBSD: setvbuf.c,v 1.15 2022/09/28 16:44:14 gnezdo Exp $ */
 /*-
  * Copyright (c) 1990, 1993
  *	The Regents of the University of California.  All rights reserved.
@@ -31,6 +31,7 @@
  * SUCH DAMAGE.
  */
 
+#include <limits.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include "local.h"
@@ -52,7 +53,7 @@
 	 * when setting _IONBF.
 	 */
 	if (mode != _IONBF)
-		if ((mode != _IOFBF && mode != _IOLBF) || (int)size < 0)
+		if ((mode != _IOFBF && mode != _IOLBF) || size > INT_MAX)
 			return (EOF);
 
 	/*
diff --git a/libc/upstream-openbsd/lib/libc/stdlib/div.c b/libc/upstream-openbsd/lib/libc/stdlib/div.c
index beaa428..5e6164f 100644
--- a/libc/upstream-openbsd/lib/libc/stdlib/div.c
+++ b/libc/upstream-openbsd/lib/libc/stdlib/div.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: div.c,v 1.6 2015/09/13 08:31:47 guenther Exp $ */
+/*	$OpenBSD: div.c,v 1.7 2022/12/27 17:10:06 jmc Exp $ */
 /*
  * Copyright (c) 1990 Regents of the University of California.
  * All rights reserved.
@@ -46,7 +46,7 @@
 	 * words, we should always truncate the quotient towards
 	 * 0, never -infinity.
 	 *
-	 * Machine division and remainer may work either way when
+	 * Machine division and remainder may work either way when
 	 * one or both of n or d is negative.  If only one is
 	 * negative and r.quot has been truncated towards -inf,
 	 * r.rem will have the same sign as denom and the opposite
diff --git a/libc/upstream-openbsd/lib/libc/stdlib/setenv.c b/libc/upstream-openbsd/lib/libc/stdlib/setenv.c
index 15c550b..fc8e5b6 100644
--- a/libc/upstream-openbsd/lib/libc/stdlib/setenv.c
+++ b/libc/upstream-openbsd/lib/libc/stdlib/setenv.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: setenv.c,v 1.19 2016/09/21 04:38:56 guenther Exp $ */
+/*	$OpenBSD: setenv.c,v 1.20 2022/08/08 22:40:03 millert Exp $ */
 /*
  * Copyright (c) 1987 Regents of the University of California.
  * All rights reserved.
@@ -48,9 +48,10 @@
 
 	for (cp = str; *cp && *cp != '='; ++cp)
 		;
-	if (*cp != '=') {
+	if (cp == str || *cp != '=') {
+		/* '=' is the first character of string or is missing. */
 		errno = EINVAL;
-		return (-1);			/* missing `=' in string */
+		return (-1);
 	}
 
 	if (__findenv(str, (int)(cp - str), &offset) != NULL) {
diff --git a/tests/stdio_test.cpp b/tests/stdio_test.cpp
index acc7ccd..fb6bce9 100644
--- a/tests/stdio_test.cpp
+++ b/tests/stdio_test.cpp
@@ -190,6 +190,8 @@
 }
 
 TEST(STDIO_TEST, getdelim_invalid) {
+#pragma clang diagnostic push
+#pragma clang diagnostic ignored "-Wnonnull"
   FILE* fp = tmpfile();
   ASSERT_TRUE(fp != nullptr);
 
@@ -206,6 +208,7 @@
   ASSERT_EQ(getdelim(&buffer, nullptr, ' ', fp), -1);
   ASSERT_EQ(EINVAL, errno);
   fclose(fp);
+#pragma clang diagnostic pop
 }
 
 TEST(STDIO_TEST, getdelim_directory) {
@@ -260,6 +263,8 @@
 }
 
 TEST(STDIO_TEST, getline_invalid) {
+#pragma clang diagnostic push
+#pragma clang diagnostic ignored "-Wnonnull"
   FILE* fp = tmpfile();
   ASSERT_TRUE(fp != nullptr);
 
@@ -276,6 +281,7 @@
   ASSERT_EQ(getline(&buffer, nullptr, fp), -1);
   ASSERT_EQ(EINVAL, errno);
   fclose(fp);
+#pragma clang diagnostic pop
 }
 
 TEST(STDIO_TEST, printf_ssize_t) {
@@ -1944,6 +1950,8 @@
 
 TEST(STDIO_TEST, open_memstream_EINVAL) {
 #if defined(__BIONIC__)
+#pragma clang diagnostic push
+#pragma clang diagnostic ignored "-Wnonnull"
   char* p;
   size_t size;
 
@@ -1956,6 +1964,7 @@
   errno = 0;
   ASSERT_EQ(nullptr, open_memstream(&p, nullptr));
   ASSERT_EQ(EINVAL, errno);
+#pragma clang diagnostic pop
 #else
   GTEST_SKIP() << "glibc is broken";
 #endif
@@ -2975,9 +2984,6 @@
 }
 
 TEST(STDIO_TEST, snprintf_b) {
-  // Our clang doesn't know about %b/%B yet.
-#pragma clang diagnostic push
-#pragma clang diagnostic ignored "-Wformat-invalid-specifier"
   char buf[BUFSIZ];
   EXPECT_EQ(5, snprintf(buf, sizeof(buf), "<%b>", 5));
   EXPECT_STREQ("<101>", buf);
@@ -2989,13 +2995,9 @@
   EXPECT_STREQ("<0b10101010101010101010101010101010>", buf);
   EXPECT_EQ(3, snprintf(buf, sizeof(buf), "<%#b>", 0));
   EXPECT_STREQ("<0>", buf);
-#pragma clang diagnostic pop
 }
 
 TEST(STDIO_TEST, snprintf_B) {
-  // Our clang doesn't know about %b/%B yet.
-#pragma clang diagnostic push
-#pragma clang diagnostic ignored "-Wformat-invalid-specifier"
   char buf[BUFSIZ];
   EXPECT_EQ(5, snprintf(buf, sizeof(buf), "<%B>", 5));
   EXPECT_STREQ("<101>", buf);
@@ -3007,13 +3009,9 @@
   EXPECT_STREQ("<0B10101010101010101010101010101010>", buf);
   EXPECT_EQ(3, snprintf(buf, sizeof(buf), "<%#B>", 0));
   EXPECT_STREQ("<0>", buf);
-#pragma clang diagnostic pop
 }
 
 TEST(STDIO_TEST, swprintf_b) {
-  // Our clang doesn't know about %b/%B yet.
-#pragma clang diagnostic push
-#pragma clang diagnostic ignored "-Wformat-invalid-specifier"
   wchar_t buf[BUFSIZ];
   EXPECT_EQ(5, swprintf(buf, sizeof(buf), L"<%b>", 5));
   EXPECT_EQ(std::wstring(L"<101>"), buf);
@@ -3025,13 +3023,9 @@
   EXPECT_EQ(std::wstring(L"<0b10101010101010101010101010101010>"), buf);
   EXPECT_EQ(3, swprintf(buf, sizeof(buf), L"<%#b>", 0));
   EXPECT_EQ(std::wstring(L"<0>"), buf);
-#pragma clang diagnostic pop
 }
 
 TEST(STDIO_TEST, swprintf_B) {
-  // Our clang doesn't know about %b/%B yet.
-#pragma clang diagnostic push
-#pragma clang diagnostic ignored "-Wformat-invalid-specifier"
   wchar_t buf[BUFSIZ];
   EXPECT_EQ(5, swprintf(buf, sizeof(buf), L"<%B>", 5));
   EXPECT_EQ(std::wstring(L"<101>"), buf);
@@ -3043,7 +3037,6 @@
   EXPECT_EQ(std::wstring(L"<0B10101010101010101010101010101010>"), buf);
   EXPECT_EQ(3, swprintf(buf, sizeof(buf), L"<%#B>", 0));
   EXPECT_EQ(std::wstring(L"<0>"), buf);
-#pragma clang diagnostic pop
 }
 
 TEST(STDIO_TEST, scanf_i_decimal) {
@@ -3143,10 +3136,6 @@
 }
 
 TEST(STDIO_TEST, scanf_b) {
-  // Our clang doesn't know about %b yet.
-#pragma clang diagnostic push
-#pragma clang diagnostic ignored "-Wformat"
-#pragma clang diagnostic ignored "-Wformat-invalid-specifier"
   int i;
   char ch;
   EXPECT_EQ(2, sscanf("<1012>", "<%b%c>", &i, &ch));
@@ -3159,14 +3148,9 @@
   EXPECT_EQ(2, sscanf("-0b", "%i%c", &i, &ch));
   EXPECT_EQ(0, i);
   EXPECT_EQ('b', ch);
-#pragma clang diagnostic pop
 }
 
 TEST(STDIO_TEST, swscanf_b) {
-  // Our clang doesn't know about %b yet.
-#pragma clang diagnostic push
-#pragma clang diagnostic ignored "-Wformat"
-#pragma clang diagnostic ignored "-Wformat-invalid-specifier"
   int i;
   char ch;
   EXPECT_EQ(2, swscanf(L"<1012>", L"<%b%c>", &i, &ch));
@@ -3179,5 +3163,4 @@
   EXPECT_EQ(2, swscanf(L"-0b", L"%i%c", &i, &ch));
   EXPECT_EQ(0, i);
   EXPECT_EQ('b', ch);
-#pragma clang diagnostic pop
 }