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, 11 insertions, 4 deletions

diff --git a/include/err.h b/include/err.h
index 5e33f9e4..a6505c36 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
 }