Mark the event_err() functions as __attribute__((noreturn))

This attribute tells gcc (and anything else that understands gcc
attributes) that the functions will never return control, and helps
the optimizer a little.  With luck, it will also tell
less-than-full-program dataflow analysis tools that they don't need to
worry about any code path that involves calling one of these functions
and then returning.

This patch also forces event_exit() to always exit, no matter what the
user-supplied fatal_callback does.  This means that the old unit tests
for the event_err* functions don't work any more, since they assume it
is safe to call event_err* if you've given it a bogus fatal_callback
that doesn't exit.  Instead, we have to make the unit tests fork
before calling event_err(), and have the main unit test process wait
for the event_err() test to exit with a sane exit code.  On unix,
that's trivial.  On windows, let's not bother and just assume that
event_err* works.

1 files changed, 5 insertions, 3 deletions

diff --git a/log-internal.h b/log-internal.h
index 786a92c7..3545da9d 100644
--- a/log-internal.h
+++ b/log-internal.h
@@ -31,17 +31,19 @@
 
 #ifdef __GNUC__
 #define EV_CHECK_FMT(a,b) __attribute__((format(printf, a, b)))
+#define EV_NORETURN __attribute__((noreturn))
 #else
 #define EV_CHECK_FMT(a,b)
+#define EV_NORETURN
 #endif
 
 #define _EVENT_ERR_ABORT 0xdeaddead
 
-void event_err(int eval, const char *fmt, ...) EV_CHECK_FMT(2,3);
+void event_err(int eval, const char *fmt, ...) EV_CHECK_FMT(2,3) EV_NORETURN;
 void event_warn(const char *fmt, ...) EV_CHECK_FMT(1,2);
-void event_sock_err(int eval, evutil_socket_t sock, const char *fmt, ...) EV_CHECK_FMT(3,4);
+void event_sock_err(int eval, evutil_socket_t sock, const char *fmt, ...) EV_CHECK_FMT(3,4) EV_NORETURN;
 void event_sock_warn(evutil_socket_t sock, const char *fmt, ...) EV_CHECK_FMT(2,3);
-void event_errx(int eval, const char *fmt, ...) EV_CHECK_FMT(2,3);
+void event_errx(int eval, const char *fmt, ...) EV_CHECK_FMT(2,3) EV_NORETURN;
 void event_warnx(const char *fmt, ...) EV_CHECK_FMT(1,2);
 void event_msgx(const char *fmt, ...) EV_CHECK_FMT(1,2);
 void _event_debugx(const char *fmt, ...) EV_CHECK_FMT(1,2);