add _Noreturn function attribute, with fallback for pre-C11 GNUC

include/setjmp.h

@@ -5,6 +5,13 @@
 extern "C" {
 #endif
 
+#if __STDC_VERSION__ >= 201112L
+#elif defined(__GNUC__)
+#define _Noreturn __attribute__((__noreturn__))
+#else
+#define _Noreturn
+#endif
+
 #include <bits/setjmp.h>
 
 
@@ -29,7 +36,7 @@ void _longjmp (jmp_buf, int);
 
 
 int setjmp (jmp_buf);
-void longjmp (jmp_buf, int);
+_Noreturn void longjmp (jmp_buf, int);
 
 #define setjmp setjmp
 #define longjmp longjmp

include/stdlib.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
+
 #undef NULL
 #ifdef __cplusplus
 #define NULL 0
@@ -46,12 +53,12 @@ void *realloc (void *, size_t);
 void free (void *);
 void *aligned_alloc(size_t alignment, size_t size);
 
-void abort (void);
+_Noreturn void abort (void);
 int atexit (void (*) (void));
-void exit (int);
-void _Exit (int);
+_Noreturn void exit (int);
+_Noreturn void _Exit (int);
 int at_quick_exit (void (*) (void));
-void quick_exit (int);
+_Noreturn void quick_exit (int);
 
 char *getenv (const char *);
 

src/exit/_Exit.c

 #include <stdlib.h>
 #include "syscall.h"
 
-void _Exit(int ec)
+_Noreturn void _Exit(int ec)
 {
 	__syscall(SYS_exit_group, ec);
 	__syscall(SYS_exit, ec);

src/exit/abort.c

@@ -2,7 +2,7 @@
 #include <signal.h>
 #include "syscall.h"
 
-void abort(void)
+_Noreturn void abort(void)
 {
 	raise(SIGABRT);
 	raise(SIGKILL);

src/exit/exit.c

@@ -14,7 +14,7 @@ weak_alias(dummy, __funcs_on_exit);
 weak_alias(dummy, __flush_on_exit);
 weak_alias(dummy, __seek_on_exit);
 
-void exit(int code)
+_Noreturn void exit(int code)
 {
 	static int lock;
 

src/exit/quick_exit.c

@@ -6,7 +6,7 @@
 static void dummy() { }
 weak_alias(dummy, __funcs_on_quick_exit);
 
-void quick_exit(int code)
+_Noreturn void quick_exit(int code)
 {
 	static int lock;
 	while (a_swap(&lock, 1)) __syscall(SYS_pause);