diff --git a/include/assert.h b/include/assert.h
index bad2ccd04cf3bbc9abe39c2f26ef9b8680d60a9e..30a43d68fae741b6a8b05cd4451da70f984e4fba 100644
--- a/include/assert.h
+++ b/include/assert.h
@@ -1,5 +1,12 @@
 #undef assert
 
+#if __STDC_VERSION__ >= 201112L
+#elif defined(__GNUC__)
+#define _Noreturn __attribute__((__noreturn__))
+#else
+#define _Noreturn
+#endif
+
 #ifdef NDEBUG
 #define	assert(x) (void)0
 #else
@@ -10,7 +17,7 @@
 extern "C" {
 #endif
 
-void __assert_fail (const char *, const char *, int, const char *);
+_Noreturn void __assert_fail (const char *, const char *, int, const char *);
 
 #ifdef __cplusplus
 }
diff --git a/include/err.h b/include/err.h
index 5e33f9e42e4508e2c6c53214e714388d73923471..a6505c366820cd74007bd83007f957e6257692ba 100644
--- a/include/err.h
+++ b/include/err.h
@@ -1,6 +1,13 @@
 #ifndef _ERR_H
 #define _ERR_H
 
+#if __STDC_VERSION__ >= 201112L
+#elif defined(__GNUC__)
+#define _Noreturn __attribute__((__noreturn__))
+#else
+#define _Noreturn
+#endif
+
 #include <stdarg.h>
 
 #ifdef __cplusplus
@@ -12,10 +19,10 @@ void vwarn(const char *, va_list);
 void warnx(const char *, ...);
 void vwarnx(const char *, va_list);
 
-void err(int, const char *, ...);
-void verr(int, const char *, va_list);
-void errx(int, const char *, ...);
-void verrx(int, const char *, va_list);
+_Noreturn void err(int, const char *, ...);
+_Noreturn void verr(int, const char *, va_list);
+_Noreturn void errx(int, const char *, ...);
+_Noreturn void verrx(int, const char *, va_list);
 
 #ifdef __cplusplus
 }
diff --git a/include/pthread.h b/include/pthread.h
index 417156c883d56481d34085f68155a22cbd0460c0..bc0d9f1c32bc3ef8a8ca6ea409eb4d5e0462434a 100644
--- a/include/pthread.h
+++ b/include/pthread.h
@@ -10,6 +10,13 @@ extern "C" {
 #define __restrict
 #endif
 
+#if __STDC_VERSION__ >= 201112L
+#elif defined(__GNUC__)
+#define _Noreturn __attribute__((__noreturn__))
+#else
+#define _Noreturn
+#endif
+
 #define __NEED_time_t
 #define __NEED_clockid_t
 #define __NEED_struct_timespec
@@ -79,7 +86,7 @@ extern "C" {
 
 int pthread_create(pthread_t *__restrict, const pthread_attr_t *__restrict, void *(*)(void *), void *__restrict);
 int pthread_detach(pthread_t);
-void pthread_exit(void *);
+_Noreturn void pthread_exit(void *);
 int pthread_join(pthread_t, void **);
 
 #ifdef __GNUC__
diff --git a/include/setjmp.h b/include/setjmp.h
index 8ec5c6f185705390dbbf56a78e0010e04ad1a8a0..e5877b4468f90f4c39efa1d959451f12534cdf7d 100644
--- a/include/setjmp.h
+++ b/include/setjmp.h
@@ -24,14 +24,14 @@ typedef struct {
 	unsigned long __ss[128/sizeof(long)];
 } sigjmp_buf[1];
 int sigsetjmp (sigjmp_buf, int);
-void siglongjmp (sigjmp_buf, int);
+_Noreturn void siglongjmp (sigjmp_buf, int);
 #endif
 
 
 #if defined(_XOPEN_SOURCE) || defined(_GNU_SOURCE) \
  || defined(_BSD_SOURCE)
 int _setjmp (jmp_buf);
-void _longjmp (jmp_buf, int);
+_Noreturn void _longjmp (jmp_buf, int);
 #endif
 
 
diff --git a/include/unistd.h b/include/unistd.h
index ecb23f81e6e453f32758017b42c8acbf64473d3b..20ba6ccbf94be32cf2444a5099b2c0a77f72a88a 100644
--- a/include/unistd.h
+++ b/include/unistd.h
@@ -11,6 +11,13 @@ extern "C" {
 #define __restrict
 #endif
 
+#if __STDC_VERSION__ >= 201112L
+#elif defined(__GNUC__)
+#define _Noreturn __attribute__((__noreturn__))
+#else
+#define _Noreturn
+#endif
+
 #define STDIN_FILENO  0
 #define STDOUT_FILENO 1
 #define STDERR_FILENO 2
@@ -90,7 +97,7 @@ int execl(const char *, const char *, ...);
 int execvp(const char *, char *const []);
 int execlp(const char *, const char *, ...);
 int fexecve(int, char *const [], char *const []);
-void _exit(int);
+_Noreturn void _exit(int);
 
 pid_t getpid(void);
 pid_t getppid(void);
diff --git a/src/exit/_Exit.c b/src/exit/_Exit.c
index c00a2ffbc798b2a5243c017d9b5292fb2afcc2bb..7a6115c7bbc71265929b20c8817d8476ee184b39 100644
--- a/src/exit/_Exit.c
+++ b/src/exit/_Exit.c
@@ -4,5 +4,5 @@
 _Noreturn void _Exit(int ec)
 {
 	__syscall(SYS_exit_group, ec);
-	__syscall(SYS_exit, ec);
+	for (;;) __syscall(SYS_exit, ec);
 }
diff --git a/src/exit/assert.c b/src/exit/assert.c
index e87442a7c50d9ca8fdf267d7c6038780941c56d3..49b0dc3ec434c68a92ad3c38f087aec74c45e4e3 100644
--- a/src/exit/assert.c
+++ b/src/exit/assert.c
@@ -1,7 +1,7 @@
 #include <stdio.h>
 #include <stdlib.h>
 
-void __assert_fail(const char *expr, const char *file, int line, const char *func)
+_Noreturn void __assert_fail(const char *expr, const char *file, int line, const char *func)
 {
 	fprintf(stderr, "Assertion failed: %s (%s: %s: %d)\n", expr, file, func, line);
 	fflush(NULL);
diff --git a/src/linux/err.c b/src/linux/err.c
index c291136dec3af739d5c46e8604c91ca6bc976f65..0f7485388ff0fd892b8937f464a5fe33b0d0c719 100644
--- a/src/linux/err.c
+++ b/src/linux/err.c
@@ -15,13 +15,13 @@ void vwarnx(const char *fmt, va_list ap)
 	putc('\n', stderr);
 }
 
-void verr(int status, const char *fmt, va_list ap)
+_Noreturn void verr(int status, const char *fmt, va_list ap)
 {
 	vwarn(fmt, ap);
 	exit(status);
 }
 
-void verrx(int status, const char *fmt, va_list ap)
+_Noreturn void verrx(int status, const char *fmt, va_list ap)
 {
 	vwarnx(fmt, ap);
 	exit(status);
@@ -43,7 +43,7 @@ void warnx(const char *fmt, ...)
 	va_end(ap);
 }
 
-void err(int status, const char *fmt, ...)
+_Noreturn void err(int status, const char *fmt, ...)
 {
 	va_list ap;
 	va_start(ap, fmt);
@@ -51,7 +51,7 @@ void err(int status, const char *fmt, ...)
 	va_end(ap);
 }
 
-void errx(int status, const char *fmt, ...)
+_Noreturn void errx(int status, const char *fmt, ...)
 {
 	va_list ap;
 	va_start(ap, fmt);
diff --git a/src/signal/siglongjmp.c b/src/signal/siglongjmp.c
index e9a6131417de5624662c6d899f74d1d0de5c527b..d0e4f67d3bccf9c2f201ca30e1cf9f23a839a616 100644
--- a/src/signal/siglongjmp.c
+++ b/src/signal/siglongjmp.c
@@ -3,7 +3,7 @@
 #include <stdlib.h>
 #include "syscall.h"
 
-void siglongjmp(sigjmp_buf buf, int ret)
+_Noreturn void siglongjmp(sigjmp_buf buf, int ret)
 {
 	if (buf->__fl) __syscall(SYS_rt_sigprocmask, SIG_SETMASK,
 		buf->__ss, 0, __SYSCALL_SSLEN);
diff --git a/src/thread/pthread_create.c b/src/thread/pthread_create.c
index 4567b41c68d3458376b6235d0e355c6ab86125ba..d8b8f0fcf8383ce3db3cddb833983c077e904f7e 100644
--- a/src/thread/pthread_create.c
+++ b/src/thread/pthread_create.c
@@ -8,7 +8,7 @@ weak_alias(dummy_0, __synccall_lock);
 weak_alias(dummy_0, __synccall_unlock);
 weak_alias(dummy_0, __pthread_tsd_run_dtors);
 
-void pthread_exit(void *result)
+_Noreturn void pthread_exit(void *result)
 {
 	pthread_t self = pthread_self();
 	int n;
@@ -43,7 +43,7 @@ void pthread_exit(void *result)
 		__unmapself(self->map_base, self->map_size);
 	}
 
-	__syscall(SYS_exit, 0);
+	for (;;) __syscall(SYS_exit, 0);
 }
 
 void __do_cleanup_push(struct __ptcb *cb)
diff --git a/src/unistd/_exit.c b/src/unistd/_exit.c
index d2e84c4cae4c8ae16404857a6905625d9da98d65..769948232e46e8be03cd2530f37b60b62d864ae1 100644
--- a/src/unistd/_exit.c
+++ b/src/unistd/_exit.c
@@ -1,7 +1,7 @@
 #include <unistd.h>
 #include <stdlib.h>
 
-void _exit(int status)
+_Noreturn void _exit(int status)
 {
 	_Exit(status);
 }