diff --git a/libc/include/features.h b/libc/include/features.h
index bc5f8a37..3cdcd4b2 100644
--- a/libc/include/features.h
+++ b/libc/include/features.h
@@ -74,8 +74,24 @@
 	#endif
 #endif
 
-#ifndef restrict
-#define restrict
+/* Detect whether the restrict keyword is available. */
+#if __STDC_VERSION__ >= 199901L
+#define __HAS_RESTRICT 1
+#endif
+
+/* Use the real restrict keyword if it is available. Not that this really
+   matters as gcc uses __restrict and __restrict__ as aliases for restrict, but
+   it will look nicer after preprocessing. */
+#if __HAS_RESTRICT
+#undef __restrict
+#define __restrict restrict
+#endif
+
+/* Provide the restrict keyword when building the C library. */
+#if !__HAS_RESTRICT && defined(LIBC_LIBRARY)
+#define restrict __restrict
+#undef __HAS_RESTRICT
+#define __HAS_RESTRICT 2
 #endif
 
 /* TODO: Improve these declarations, perhaps like they are in glibc. */
diff --git a/libc/include/netdb.h b/libc/include/netdb.h
index 550f7ada..7640fd16 100644
--- a/libc/include/netdb.h
+++ b/libc/include/netdb.h
@@ -118,11 +118,11 @@ void endprotoent(void);
 void endservent(void);
 void freeaddrinfo(struct addrinfo*);
 const char* gai_strerror(int);
-int getaddrinfo(const char* restrict, const char* restrict,
-                const struct addrinfo* restrict, struct addrinfo** restrict);
+int getaddrinfo(const char* __restrict, const char* __restrict,
+                const struct addrinfo* __restrict, struct addrinfo** __restrict);
 struct hostent* gethostent(void);
-int getnameinfo(const struct sockaddr* restrict, socklen_t, char* restrict,
-                socklen_t, char* restrict, socklen_t, int);
+int getnameinfo(const struct sockaddr* __restrict, socklen_t, char* __restrict,
+                socklen_t, char* __restrict, socklen_t, int);
 struct netent* getnetbyaddr(uint32_t, int);
 struct netent* getnetbyname(const char*);
 struct netent* getnetent(void);
diff --git a/libc/include/stdio.h b/libc/include/stdio.h
index d1a4b86a..119fc409 100644
--- a/libc/include/stdio.h
+++ b/libc/include/stdio.h
@@ -80,27 +80,27 @@ extern int ferror(FILE* stream);
 extern int fflush(FILE* stream);
 extern int fileno(FILE* stream);
 extern int fgetc(FILE* stream);
-extern char* fgets(char* restrict s, int n, FILE* restrict stream);
-extern FILE* fopen(const char* restrict filename, const char* restrict mode);
-extern int fprintf(FILE* restrict stream, const char* restrict format, ...);
+extern char* fgets(char* __restrict s, int n, FILE* __restrict stream);
+extern FILE* fopen(const char* __restrict filename, const char* __restrict mode);
+extern int fprintf(FILE* __restrict stream, const char* __restrict format, ...);
 extern int fputc(int c, FILE* stream);
-extern int fputs(const char* restrict s, FILE* restrict stream);
-extern size_t fread(void* restrict ptr, size_t size, size_t nitems, FILE* restrict stream);
-extern FILE* freopen(const char* restrict filename, const char *restrict mode, FILE* restrict stream);
-extern int fscanf(FILE* restrict stream, const char* restrict format, ... );
+extern int fputs(const char* __restrict s, FILE* __restrict stream);
+extern size_t fread(void* __restrict ptr, size_t size, size_t nitems, FILE* __restrict stream);
+extern FILE* freopen(const char* __restrict filename, const char *__restrict mode, FILE* __restrict stream);
+extern int fscanf(FILE* __restrict stream, const char* __restrict format, ... );
 extern int fseek(FILE* stream, long offset, int whence);
 extern int fseeko(FILE* stream, off_t offset, int whence);
 extern long ftell(FILE* stream);
 extern off_t ftello(FILE* stream);
-extern size_t fwrite(const void* restrict ptr, size_t size, size_t nitems, FILE* restrict stream);
+extern size_t fwrite(const void* __restrict ptr, size_t size, size_t nitems, FILE* __restrict stream);
 extern int getc(FILE* stream);
 extern int getchar(void);
-extern ssize_t getdelim(char** restrict lineptr, size_t* restrict n, int delimiter, FILE* restrict stream);
-extern ssize_t getline(char** restrict lineptr, size_t* restrict n, FILE* restrict stream);
+extern ssize_t getdelim(char** __restrict lineptr, size_t* __restrict n, int delimiter, FILE* __restrict stream);
+extern ssize_t getline(char** __restrict lineptr, size_t* __restrict n, FILE* __restrict stream);
 extern int pclose(FILE* steam);
 extern void perror(const char* s);
 extern FILE* popen(const char* command, const char* mode);
-extern int printf(const char* restrict format, ...);
+extern int printf(const char* __restrict format, ...);
 extern int putc(int c, FILE* stream);
 extern int putchar(int c);
 extern int puts(const char* str);
@@ -109,38 +109,38 @@ extern int remove(const char* path);
 extern int renameat(int oldfd, const char* oldname, int newfd, const char* newname);
 extern int rename(const char* oldname, const char* newname);
 extern void rewind(FILE* stream);
-extern int snprintf(char* restrict s, size_t n, const char* restrict format, ...);
-extern void setbuf(FILE* restrict stream, char* restrict buf);
-extern int setvbuf(FILE* restrict stream, char* restrict buf, int type, size_t size);
+extern int snprintf(char* __restrict s, size_t n, const char* __restrict format, ...);
+extern void setbuf(FILE* __restrict stream, char* __restrict buf);
+extern int setvbuf(FILE* __restrict stream, char* __restrict buf, int type, size_t size);
 extern char* sortix_gets(void);
 extern int sortix_puts(const char* str);
-extern int sprintf(char* restrict s, const char* restrict format, ...);
-extern int scanf(const char* restrict format, ...);
-extern int sscanf(const char* restrict s, const char* restrict format, ...);
+extern int sprintf(char* __restrict s, const char* __restrict format, ...);
+extern int scanf(const char* __restrict format, ...);
+extern int sscanf(const char* __restrict s, const char* __restrict format, ...);
 extern FILE* tmpfile(void);
 extern int ungetc(int c, FILE* stream);
-extern int vfprintf(FILE* restrict stream, const char* restrict format, __gnuc_va_list ap);
-extern int vfscanf(FILE* restrict stream, const char* restrict format, __gnuc_va_list arg);
-extern int vprintf(const char* restrict format, __gnuc_va_list ap);
-extern int vscanf(const char* restrict format, __gnuc_va_list arg);
-extern int vsnprintf(char* restrict, size_t, const char* restrict, __gnuc_va_list);
-extern int vsprintf(char* restrict s, const char* restrict format, __gnuc_va_list ap);
-extern int vsscanf(const char* restrict s, const char* restrict format, __gnuc_va_list arg);
+extern int vfprintf(FILE* __restrict stream, const char* __restrict format, __gnuc_va_list ap);
+extern int vfscanf(FILE* __restrict stream, const char* __restrict format, __gnuc_va_list arg);
+extern int vprintf(const char* __restrict format, __gnuc_va_list ap);
+extern int vscanf(const char* __restrict format, __gnuc_va_list arg);
+extern int vsnprintf(char* __restrict, size_t, const char* __restrict, __gnuc_va_list);
+extern int vsprintf(char* __restrict s, const char* __restrict format, __gnuc_va_list ap);
+extern int vsscanf(const char* __restrict s, const char* __restrict format, __gnuc_va_list arg);
 
 /* TODO: These are not implemented in sortix libc yet. */
 #if defined(__SORTIX_SHOW_UNIMPLEMENTED)
 extern char* ctermid(char* s);
-extern FILE *fmemopen(void* restrict buf, size_t size, const char* restrict mode);
+extern FILE *fmemopen(void* __restrict buf, size_t size, const char* __restrict mode);
 extern FILE* open_memstream(char** bufp, size_t* sizep);
-extern int dprintf(int fildes, const char* restrict format, ...);
-extern int fgetpos(FILE* restrict stream, fpos_t* restrict pos);
+extern int dprintf(int fildes, const char* __restrict format, ...);
+extern int fgetpos(FILE* __restrict stream, fpos_t* __restrict pos);
 extern int fsetpos(FILE* stream, const fpos_t* pos);
 extern int ftrylockfile(FILE* file);
 extern int getchar_unlocked(void);
 extern int getc_unlocked(FILE* stream);
 extern int putchar_unlocked(int c);
 extern int putc_unlocked(int c, FILE* steam);
-extern int vdprintf(int fildes, const char* restrict format, __gnuc_va_list ap);
+extern int vdprintf(int fildes, const char* __restrict format, __gnuc_va_list ap);
 extern void flockfile(FILE* file);
 extern void funlockfile(FILE* file);
 
@@ -190,7 +190,7 @@ extern char* gets(void) asm ("sortix_gets");
 #if defined(_SORTIX_SOURCE) || defined(_WANT_SORTIX_VPRINTF_CALLBACK)
 extern size_t vprintf_callback(size_t (*callback)(void*, const char*, size_t),
                                void* user,
-                               const char* restrict format,
+                               const char* __restrict format,
                                __gnuc_va_list ap);
 #endif
 
diff --git a/libc/include/stdlib.h b/libc/include/stdlib.h
index e8ae6597..ba9e3b11 100644
--- a/libc/include/stdlib.h
+++ b/libc/include/stdlib.h
@@ -81,8 +81,8 @@ ldiv_t ldiv(long, long);
 long long llabs(long long);
 lldiv_t lldiv(long long, long long);
 void* malloc(size_t);
-size_t mbstowcs(wchar_t* restrict, const char* restrict, size_t);
-int mbtowc(wchar_t *restrict, const char* restrict, size_t);
+size_t mbstowcs(wchar_t* __restrict, const char* __restrict, size_t);
+int mbtowc(wchar_t *__restrict, const char* __restrict, size_t);
 #if !defined(_SORTIX_SOURCE)
 char* mktemp(char* templ);
 #endif
@@ -91,16 +91,16 @@ int putenv(char*);
 void qsort(void*, size_t, size_t, int (*)(const void*, const void*));
 int rand(void);
 void* realloc(void*, size_t);
-char* realpath(const char* restrict, char* restrict);
+char* realpath(const char* __restrict, char* __restrict);
 int setenv(const char*, const char*, int);
 void srand(unsigned);
-long strtol(const char* restrict, char** restrict, int);
-unsigned long strtoul(const char* restrict, char** restrict, int);
-unsigned long long strtoull(const char* restrict, char** restrict, int);
-long long strtoll(const char* restrict, char** restrict, int);
+long strtol(const char* __restrict, char** __restrict, int);
+unsigned long strtoul(const char* __restrict, char** __restrict, int);
+unsigned long long strtoull(const char* __restrict, char** __restrict, int);
+long long strtoll(const char* __restrict, char** __restrict, int);
 int system(const char*);
 int unsetenv(const char*);
-size_t wcstombs(char* restrict, const wchar_t *restrict, size_t);
+size_t wcstombs(char* __restrict, const wchar_t *__restrict, size_t);
 int wctomb(char*, wchar_t);
 
 #if defined(_SORTIX_SOURCE) || defined(_WANT_SORTIX_ENV)
@@ -146,9 +146,9 @@ void setkey(const char*);
 char* setstate(char*);
 void srand48(long);
 void srandom(unsigned);
-double strtod(const char* restrict, char** restrict);
-float strtof(const char* restrict, char** restrict);
-long double strtold(const char* restrict, char** restrict);
+double strtod(const char* __restrict, char** __restrict);
+float strtof(const char* __restrict, char** __restrict);
+long double strtold(const char* __restrict, char** __restrict);
 int unlockpt(int);
 
 #if __POSIX_OBSOLETE <= 200801
diff --git a/libc/include/string.h b/libc/include/string.h
index 9e271953..70004735 100644
--- a/libc/include/string.h
+++ b/libc/include/string.h
@@ -34,41 +34,41 @@ __BEGIN_DECLS
 @include(size_t.h)
 @include(locale_t.h)
 
-void* memccpy(void* restrict, const void* restrict, int, size_t);
+void* memccpy(void* __restrict, const void* __restrict, int, size_t);
 void* memchr(const void*, int, size_t);
 int memcmp(const void*, const void*, size_t);
-void* memcpy(void* restrict, const void* restrict, size_t);
+void* memcpy(void* __restrict, const void* __restrict, size_t);
 void* memmove(void*, const void*, size_t);
 void* memset(void*, int, size_t);
-char* stpcpy(char* restrict, const char* restrict);
-char* stpncpy(char* restrict, const char* restrict, size_t);
-char* strcat(char* restrict, const char* restrict);
+char* stpcpy(char* __restrict, const char* __restrict);
+char* stpncpy(char* __restrict, const char* __restrict, size_t);
+char* strcat(char* __restrict, const char* __restrict);
 char* strchr(const char*, int);
 int strcmp(const char*, const char*);
 int strcoll(const char*, const char*);
 size_t strcspn(const char*, const char*);
-char* strcpy(char* restrict, const char* restrict);
+char* strcpy(char* __restrict, const char* __restrict);
 char* strdup(const char*);
 size_t strlen(const char*);
-char* strncat(char* restrict, const char* restrict, size_t);
+char* strncat(char* __restrict, const char* __restrict, size_t);
 int strncmp(const char*, const char*, size_t);
-char* strncpy(char* restrict, const char* restrict, size_t);
+char* strncpy(char* __restrict, const char* __restrict, size_t);
 char* strndup(const char*, size_t);
 size_t strnlen(const char*, size_t);
 char* strpbrk(const char*, const char*);
 char* strrchr(const char*, int);
 size_t strspn(const char*, const char*);
 char* strstr(const char*, const char*);
-char* strtok(char* restrict, const char* restrict);
-char* strtok_r(char* restrict, const char* restrict, char** restrict);
-size_t strxfrm(char* restrict, const char* restrict, size_t);
+char* strtok(char* __restrict, const char* __restrict);
+char* strtok_r(char* __restrict, const char* __restrict, char** __restrict);
+size_t strxfrm(char* __restrict, const char* __restrict, size_t);
 
 /* TODO: These are not implemented in sortix libc yet. */
 #if defined(__SORTIX_SHOW_UNIMPLEMENTED)
 int strcoll_l(const char*, const char*, locale_t);
 char* strerror_l(int, locale_t);
 int strerror_r(int, char*, size_t);
-size_t strxfrm_l(char* restrict, const char* restrict, size_t, locale_t);
+size_t strxfrm_l(char* __restrict, const char* __restrict, size_t, locale_t);
 #endif
 
 #if defined(_SORTIX_SOURCE) || defined(_GNU_SOURCE)
diff --git a/libc/include/sys/select.h b/libc/include/sys/select.h
index 12572861..9be2114e 100644
--- a/libc/include/sys/select.h
+++ b/libc/include/sys/select.h
@@ -60,8 +60,8 @@ typedef struct
 #define FD_ZERO(fdsetp) memset(fdsetp, 0, sizeof(fd_set))
 
 /* TODO: pselect */
-int select(int, fd_set* restrict, fd_set* restrict, fd_set* restrict,
-           struct timeval* restrict);
+int select(int, fd_set* __restrict, fd_set* __restrict, fd_set* __restrict,
+           struct timeval* __restrict);
 
 __END_DECLS
 
diff --git a/libc/include/sys/socket.h b/libc/include/sys/socket.h
index 5b1d0f60..1cbceade 100644
--- a/libc/include/sys/socket.h
+++ b/libc/include/sys/socket.h
@@ -132,17 +132,17 @@ struct linger
 #define SHUT_RDWR 1
 #define SHUT_WR 2
 
-int accept4(int, struct sockaddr* restrict, socklen_t* restrict, int);
-int accept(int, struct sockaddr* restrict, socklen_t* restrict);
+int accept4(int, struct sockaddr* __restrict, socklen_t* __restrict, int);
+int accept(int, struct sockaddr* __restrict, socklen_t* __restrict);
 int bind(int, const struct sockaddr*, socklen_t);
 int connect(int, const struct sockaddr*, socklen_t);
-int getpeername(int, struct sockaddr* restrict, socklen_t* restrict);
-int getsockname(int, struct sockaddr* restrict, socklen_t* restrict);
-int getsockopt(int, int, int, void* restrict, socklen_t* restrict);
+int getpeername(int, struct sockaddr* __restrict, socklen_t* __restrict);
+int getsockname(int, struct sockaddr* __restrict, socklen_t* __restrict);
+int getsockopt(int, int, int, void* __restrict, socklen_t* __restrict);
 int listen(int, int);
 ssize_t recv(int, void*, size_t, int);
-ssize_t recvfrom(int, void* restrict, size_t, int,
-        struct sockaddr* restrict, socklen_t* restrict);
+ssize_t recvfrom(int, void* __restrict, size_t, int,
+        struct sockaddr* __restrict, socklen_t* __restrict);
 ssize_t recvmsg(int, struct msghdr*, int);
 ssize_t send(int, const void*, size_t, int);
 ssize_t sendmsg(int, const struct msghdr*, int);
diff --git a/libc/include/sys/stat.h b/libc/include/sys/stat.h
index 68fb7b89..e135c2be 100644
--- a/libc/include/sys/stat.h
+++ b/libc/include/sys/stat.h
@@ -61,14 +61,14 @@ int fchmodat(int dirfd, const char* path, mode_t mode, int flags);
 int fstat(int fd, struct stat* st);
 int fstatat(int dirfd, const char* path, struct stat* buf, int flags);
 int futimens(int fd, const struct timespec times[2]);
-int lstat(const char* restrict path, struct stat* restrict st);
+int lstat(const char* __restrict path, struct stat* __restrict st);
 int mkdir(const char* path, mode_t mode);
 int mkdirat(int dirfd, const char* path, mode_t mode);
 /* TODO: mkfifo */
 /* TODO: mkfifoat */
 /* TODO: mknod? */
 /* TODO: mknodat? */
-int stat(const char* restrict path, struct stat* restrict st);
+int stat(const char* __restrict path, struct stat* __restrict st);
 mode_t umask(mode_t mask);
 int utimens(const char* path, const struct timespec times[2]);
 int utimensat(int dirfd, const char* path, const struct timespec times[2],
diff --git a/libc/include/sys/time.h b/libc/include/sys/time.h
index 6bcd030f..7f040e5a 100644
--- a/libc/include/sys/time.h
+++ b/libc/include/sys/time.h
@@ -33,7 +33,7 @@ __BEGIN_DECLS
 @include(suseconds_t.h)
 @include(timeval.h)
 
-int gettimeofday(struct timeval* restrict tp, void* restrict tzp);
+int gettimeofday(struct timeval* __restrict tp, void* __restrict tzp);
 
 __END_DECLS
 
diff --git a/libc/include/time.h b/libc/include/time.h
index 2f733ce9..7c77158d 100644
--- a/libc/include/time.h
+++ b/libc/include/time.h
@@ -76,7 +76,7 @@ __BEGIN_DECLS
 /* getdate_err is omitted, use strptime */
 
 char* asctime(const struct tm*);
-char* asctime_r(const struct tm* restrict, char* restrict);
+char* asctime_r(const struct tm* __restrict, char* __restrict);
 clock_t clock(void);
 /* TODO: clock_getcpuclockid */
 int clock_getres(clockid_t, struct timespec*);
@@ -89,24 +89,24 @@ char* ctime_r(const time_t* clock, char* buf);
 double difftime(time_t, time_t);
 /* getdate is omitted, use strptime */
 struct tm* gmtime(const time_t*);
-struct tm* gmtime_r(const time_t* restrict, struct tm* restrict);
+struct tm* gmtime_r(const time_t* __restrict, struct tm* __restrict);
 struct tm* localtime(const time_t*);
-struct tm* localtime_r(const time_t* restrict, struct tm* restrict);
+struct tm* localtime_r(const time_t* __restrict, struct tm* __restrict);
 time_t mktime(struct tm*);
 int nanosleep(const struct timespec*, struct timespec*);
-size_t strftime(char* restrict, size_t, const char* restrict,
-                const struct tm* restrict);
-size_t strftime_l(char* restrict, size_t, const char* restrict,
-                const struct tm* restrict, locale_t);
-char* strptime(const char* restrict, const char* restrict,
-               struct tm* restrict);
+size_t strftime(char* __restrict, size_t, const char* __restrict,
+                const struct tm* __restrict);
+size_t strftime_l(char* __restrict, size_t, const char* __restrict,
+                const struct tm* __restrict, locale_t);
+char* strptime(const char* __restrict, const char* __restrict,
+               struct tm* __restrict);
 time_t time(time_t*);
-int timer_create(clockid_t, struct sigevent* restrict, time_t* restrict);
+int timer_create(clockid_t, struct sigevent* __restrict, time_t* __restrict);
 int timer_delete(timer_t);
 int timer_getoverrun(timer_t);
 int timer_gettime(timer_t, struct itimerspec*);
-int timer_settime(timer_t, int, const struct itimerspec* restrict,
-                  struct itimerspec* restrict);
+int timer_settime(timer_t, int, const struct itimerspec* __restrict,
+                  struct itimerspec* __restrict);
 void tzset(void);
 
 extern int daylight;
diff --git a/libc/include/unistd.h b/libc/include/unistd.h
index 5e1444e5..901f416a 100644
--- a/libc/include/unistd.h
+++ b/libc/include/unistd.h
@@ -129,7 +129,7 @@ int setpgid(pid_t, pid_t);
 int setregid(gid_t, gid_t);
 int setreuid(uid_t, uid_t);
 pid_t setsid(void);
-void swab(const void* restrict, void* restrict, ssize_t);
+void swab(const void* __restrict, void* __restrict, ssize_t);
 int symlink(const char*, const char*);
 int symlinkat(const char*, int, const char*);
 void sync(void);
@@ -183,8 +183,8 @@ long pathconf(const char*, int);
 int pipe(int [2]);
 ssize_t pread(int, void*, size_t, off_t);
 ssize_t pwrite(int, const void*, size_t, off_t);
-ssize_t readlink(const char* restrict, char* restrict, size_t);
-ssize_t readlinkat(int, const char* restrict, char* restrict, size_t);
+ssize_t readlink(const char* __restrict, char* __restrict, size_t);
+ssize_t readlinkat(int, const char* __restrict, char* __restrict, size_t);
 ssize_t read(int, void*, size_t);
 int rmdir(const char*);
 int setegid(gid_t);
diff --git a/libc/include/wchar.h b/libc/include/wchar.h
index c2333f22..7c86d0c6 100644
--- a/libc/include/wchar.h
+++ b/libc/include/wchar.h
@@ -61,63 +61,63 @@ __BEGIN_DECLS
 
 struct tm;
 
-size_t mbsrtowcs(wchar_t* restrict, const char** restrict, size_t, mbstate_t* restrict);
-size_t wcrtomb(char* restrict, wchar_t, mbstate_t* restrict);
-size_t mbrtowc(wchar_t* restrict, const char* restrict, size_t, mbstate_t* restrict);
-wchar_t* wcscat(wchar_t* restrict, const wchar_t* restrict);
+size_t mbsrtowcs(wchar_t* __restrict, const char** __restrict, size_t, mbstate_t* __restrict);
+size_t wcrtomb(char* __restrict, wchar_t, mbstate_t* __restrict);
+size_t mbrtowc(wchar_t* __restrict, const char* __restrict, size_t, mbstate_t* __restrict);
+wchar_t* wcscat(wchar_t* __restrict, const wchar_t* __restrict);
 wchar_t* wcschr(const wchar_t*, wchar_t);
 wchar_t* wcschrnul(const wchar_t*, wchar_t);
 int wcscmp(const wchar_t*, const wchar_t*);
-wchar_t* wcscpy(wchar_t* restrict, const wchar_t* restrict);
+wchar_t* wcscpy(wchar_t* __restrict, const wchar_t* __restrict);
 size_t wcscspn(const wchar_t*, const wchar_t*);
 size_t wcslen(const wchar_t*);
-wchar_t* wcsncat(wchar_t* restrict, const wchar_t* restrict, size_t);
-wchar_t* wcsncpy(wchar_t* restrict, const wchar_t* restrict, size_t);
+wchar_t* wcsncat(wchar_t* __restrict, const wchar_t* __restrict, size_t);
+wchar_t* wcsncpy(wchar_t* __restrict, const wchar_t* __restrict, size_t);
 wchar_t* wcsrchr(const wchar_t*, wchar_t);
-size_t wcsrtombs(char* restrict, const wchar_t** restrict, size_t, mbstate_t* restrict);
+size_t wcsrtombs(char* __restrict, const wchar_t** __restrict, size_t, mbstate_t* __restrict);
 size_t wcsspn(const wchar_t*, const wchar_t*);
-wchar_t* wcstok(wchar_t* restrict, const wchar_t* restrict, wchar_t** restrict);
+wchar_t* wcstok(wchar_t* __restrict, const wchar_t* __restrict, wchar_t** __restrict);
 
 /* TODO: These are not implemented in sortix libc yet. */
 #if defined(__SORTIX_SHOW_UNIMPLEMENTED)
-double wcstod(const wchar_t* restrict, wchar_t** restrict);
+double wcstod(const wchar_t* __restrict, wchar_t** __restrict);
 FILE* open_wmemstream(wchar_t** bufp, size_t* sizep);
-float wcstof(const wchar_t* restrict, wchar_t** restrict);
-int fputws(const wchar_t* restrict, FILE* restrict);
+float wcstof(const wchar_t* __restrict, wchar_t** __restrict);
+int fputws(const wchar_t* __restrict, FILE* __restrict);
 int fwide(FILE*, int);
-int fwprintf(FILE* restrict, const wchar_t* restrict, ...);
-int fwscanf(FILE* restrict, const wchar_t* restrict, ...);
+int fwprintf(FILE* __restrict, const wchar_t* __restrict, ...);
+int fwscanf(FILE* __restrict, const wchar_t* __restrict, ...);
 int mbsinit(const mbstate_t*);
-int swprintf(wchar_t* restrict, size_t, const wchar_t* restrict, ...);
-int swscanf(const wchar_t* restrict, const wchar_t* restrict, ...);
-int vfwprintf(FILE* restrict, const wchar_t* restrict, va_list);
-int vfwscanf(FILE* restrict, const wchar_t* restrict, va_list);
-int vswprintf(wchar_t* restrict, size_t, const wchar_t* restrict, va_list);
-int vswscanf(const wchar_t* restrict, const wchar_t* restrict, va_list);
-int vwprintf(const wchar_t* restrict, va_list);
-int vwscanf(const wchar_t* restrict, va_list);
+int swprintf(wchar_t* __restrict, size_t, const wchar_t* __restrict, ...);
+int swscanf(const wchar_t* __restrict, const wchar_t* __restrict, ...);
+int vfwprintf(FILE* __restrict, const wchar_t* __restrict, va_list);
+int vfwscanf(FILE* __restrict, const wchar_t* __restrict, va_list);
+int vswprintf(wchar_t* __restrict, size_t, const wchar_t* __restrict, va_list);
+int vswscanf(const wchar_t* __restrict, const wchar_t* __restrict, va_list);
+int vwprintf(const wchar_t* __restrict, va_list);
+int vwscanf(const wchar_t* __restrict, va_list);
 int wcscoll(const wchar_t*, const wchar_t*);
 int wcsncmp(const wchar_t*, const wchar_t*, size_t);
 int wcswidth(const wchar_t*, size_t);
 int wctob(wint_t);
 int wcwidth(wchar_t);
 int wmemcmp(const wchar_t*, const wchar_t*, size_t);
-int wprintf(const wchar_t* restrict, ...);
-int wscanf(const wchar_t* restrict, ...);
-long double wcstold(const wchar_t* restrict, wchar_t** restrict);
-long long wcstoll(const wchar_t* restrict, wchar_t** restrict, int);
-long wcstol(const wchar_t* restrict, wchar_t** restrict, int);
-size_t mbrlen(const char* restrict, size_t, mbstate_t* restrict);
-size_t wcsftime(wchar_t* restrict, size_t, const wchar_t* restrict, const struct tm* restrict);
-size_t wcsxfrm(wchar_t* restrict, const wchar_t* restrict, size_t);
-unsigned long long wcstoull(const wchar_t* restrict, wchar_t** restrict, int);
-unsigned long wcstoul(const wchar_t* restrict, wchar_t** restrict, int);
-wchar_t* fgetws(wchar_t* restrict, int, FILE* restrict);
+int wprintf(const wchar_t* __restrict, ...);
+int wscanf(const wchar_t* __restrict, ...);
+long double wcstold(const wchar_t* __restrict, wchar_t** __restrict);
+long long wcstoll(const wchar_t* __restrict, wchar_t** __restrict, int);
+long wcstol(const wchar_t* __restrict, wchar_t** __restrict, int);
+size_t mbrlen(const char* __restrict, size_t, mbstate_t* __restrict);
+size_t wcsftime(wchar_t* __restrict, size_t, const wchar_t* __restrict, const struct tm* __restrict);
+size_t wcsxfrm(wchar_t* __restrict, const wchar_t* __restrict, size_t);
+unsigned long long wcstoull(const wchar_t* __restrict, wchar_t** __restrict, int);
+unsigned long wcstoul(const wchar_t* __restrict, wchar_t** __restrict, int);
+wchar_t* fgetws(wchar_t* __restrict, int, FILE* __restrict);
 wchar_t* wcspbrk(const wchar_t*, const wchar_t*);
-wchar_t* wcsstr(const wchar_t* restrict, const wchar_t* restrict);
+wchar_t* wcsstr(const wchar_t* __restrict, const wchar_t* __restrict);
 wchar_t* wcswcs(const wchar_t*, const wchar_t*);
 wchar_t* wmemchr(const wchar_t*, wchar_t, size_t);
-wchar_t* wmemcpy(wchar_t* restrict, const wchar_t* restrict, size_t);
+wchar_t* wmemcpy(wchar_t* __restrict, const wchar_t* __restrict, size_t);
 wchar_t* wmemmove(wchar_t*, const wchar_t*, size_t);
 wchar_t* wmemset(wchar_t*, wchar_t, size_t);
 wint_t btowc(int);
diff --git a/libc/memcpy.cpp b/libc/memcpy.cpp
index b3887add..3303bacf 100644
--- a/libc/memcpy.cpp
+++ b/libc/memcpy.cpp
@@ -25,9 +25,6 @@
 #include <stdint.h>
 #include <string.h>
 
-#undef restrict
-#define restrict __restrict__
-
 #if 8 < __SIZEOF_LONG__
 #error unsigned long is bigger than expected, please add support to this file.
 #endif