further use of _Noreturn, for non-plain-C functions

note that POSIX does not specify these functions as _Noreturn, because
POSIX is aligned with C99, not the new C11 standard. when POSIX is
eventually updated to C11, it will almost surely give these functions
the _Noreturn attribute. for now, the actual _Noreturn keyword is not
used anyway when compiling with a c99 compiler, which is what POSIX
requires; the GCC __attribute__ is used instead if it's available,
however.

in a few places, I've added infinite for loops at the end of _Noreturn
functions to silence compiler warnings. presumably
__buildin_unreachable could achieve the same thing, but it would only
work on newer GCCs and would not be portable. the loops should have
near-zero code size cost anyway.

like the previous _Noreturn commit, this one is based on patches
contributed by philomath.

1 files changed, 8 insertions, 1 deletions

diff --git a/include/unistd.h b/include/unistd.h
index ecb23f81..20ba6ccb 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);