diff --git a/lib/isc/condition.c b/lib/isc/condition.c
index c81f3213b5..baf2808a6b 100644
--- a/lib/isc/condition.c
+++ b/lib/isc/condition.c
@@ -26,7 +26,6 @@ isc__condition_waituntil(pthread_cond_t *c, pthread_mutex_t *m, isc_time_t *t) {
 	int presult;
 	isc_result_t result;
 	struct timespec ts;
-	char strbuf[ISC_STRERRORSIZE];
 
 	REQUIRE(c != NULL && m != NULL && t != NULL);
 
@@ -61,7 +60,6 @@ isc__condition_waituntil(pthread_cond_t *c, pthread_mutex_t *m, isc_time_t *t) {
 		}
 	} while (presult == EINTR);
 
-	strerror_r(presult, strbuf, sizeof(strbuf));
-	UNEXPECTED_ERROR("pthread_cond_timedwait() returned %s", strbuf);
+	UNEXPECTED_SYSERROR(presult, "pthread_cond_timedwait()");
 	return (ISC_R_UNEXPECTED);
 }
diff --git a/lib/isc/include/isc/error.h b/lib/isc/include/isc/error.h
index ecebab60a2..96552bcb78 100644
--- a/lib/isc/include/isc/error.h
+++ b/lib/isc/include/isc/error.h
@@ -44,8 +44,4 @@ isc_error_fatal(const char *, int, const char *, ...) ISC_FORMAT_PRINTF(3, 4);
 noreturn void
 isc_error_runtimecheck(const char *, int, const char *);
 
-#define ISC_ERROR_RUNTIMECHECK(cond) \
-	((void)((cond) ||            \
-		((isc_error_runtimecheck)(__FILE__, __LINE__, #cond), 0)))
-
 ISC_LANG_ENDDECLS
diff --git a/lib/isc/include/isc/util.h b/lib/isc/include/isc/util.h
index b93ddec2a4..38b025b392 100644
--- a/lib/isc/include/isc/util.h
+++ b/lib/isc/include/isc/util.h
@@ -320,16 +320,30 @@ mock_assert(const int result, const char *const expression,
 
 #define FATAL_ERROR(...) isc_error_fatal(__FILE__, __LINE__, __VA_ARGS__)
 
+#define REPORT_SYSERROR(report, err, fmt, ...)                             \
+	{                                                                  \
+		char _strerr[ISC_STRERRORSIZE];                            \
+		strerror_r(err, _strerr, sizeof(_strerr));                 \
+		report(__FILE__, __LINE__, fmt ": %s (%d)", ##__VA_ARGS__, \
+		       _strerr, err);                                      \
+	}
+
+#define UNEXPECTED_SYSERROR(err, ...) \
+	REPORT_SYSERROR(isc_error_unexpected, err, __VA_ARGS__)
+
+#define FATAL_SYSERROR(err, ...) \
+	REPORT_SYSERROR(isc_error_fatal, err, __VA_ARGS__)
+
 #ifdef UNIT_TESTING
 
-#define RUNTIME_CHECK(expression)                                             \
-	((!(expression))                                                      \
-		 ? (mock_assert(0, #expression, __FILE__, __LINE__), abort()) \
-		 : (void)0)
+#define RUNTIME_CHECK(cond) \
+	((cond) ? (void)0   \
+		: (mock_assert(0, #cond, __FILE__, __LINE__), abort()))
 
 #else /* UNIT_TESTING */
 
-#define RUNTIME_CHECK(cond) ISC_ERROR_RUNTIMECHECK(cond)
+#define RUNTIME_CHECK(cond) \
+	((cond) ? (void)0 : isc_error_runtimecheck(__FILE__, __LINE__, #cond))
 
 #endif /* UNIT_TESTING */
 
@@ -337,13 +351,9 @@ mock_assert(const int result, const char *const expression,
  * Runtime check which logs the error value returned by a POSIX Threads
  * function and the error string that corresponds to it
  */
-#define PTHREADS_RUNTIME_CHECK(func, ret)                               \
-	if ((ret) != 0) {                                               \
-		char _strerrorbuf[ISC_STRERRORSIZE];                    \
-		strerror_r(ret, _strerrorbuf, sizeof(_strerrorbuf));    \
-		isc_error_fatal(__FILE__, __LINE__,                     \
-				"%s(): %s() failed with error %d (%s)", \
-				__func__, #func, ret, _strerrorbuf);    \
+#define PTHREADS_RUNTIME_CHECK(func, ret)                           \
+	if ((ret) != 0) {                                           \
+		FATAL_SYSERROR(ret, "%s(): %s()", __func__, #func); \
 	}
 
 /*%
diff --git a/lib/isc/include/isc/uv.h b/lib/isc/include/isc/uv.h
index 8f80b65f82..541f697b1b 100644
--- a/lib/isc/include/isc/uv.h
+++ b/lib/isc/include/isc/uv.h
@@ -46,10 +46,9 @@
  * These are used with all versions of libuv:
  */
 
-#define UV_RUNTIME_CHECK(func, ret)                                           \
-	if (ret != 0) {                                                       \
-		isc_error_fatal(__FILE__, __LINE__, "%s failed: %s\n", #func, \
-				uv_strerror(ret));                            \
+#define UV_RUNTIME_CHECK(func, ret)                                      \
+	if (ret != 0) {                                                  \
+		FATAL_ERROR("%s failed: %s\n", #func, uv_strerror(ret)); \
 	}
 
 #define isc_uverr2result(x) \
diff --git a/lib/isc/loop.c b/lib/isc/loop.c
index df414eed7c..52817be01c 100644
--- a/lib/isc/loop.c
+++ b/lib/isc/loop.c
@@ -45,14 +45,10 @@
 
 static void
 ignore_signal(int sig, void (*handler)(int)) {
-	struct sigaction sa;
+	struct sigaction sa = { .sa_handler = handler };
 
-	sa = (struct sigaction){ .sa_handler = handler };
 	if (sigfillset(&sa.sa_mask) != 0 || sigaction(sig, &sa, NULL) < 0) {
-		char strbuf[ISC_STRERRORSIZE];
-		strerror_r(errno, strbuf, sizeof(strbuf));
-		isc_error_fatal(__FILE__, __LINE__, "%s() %d setup: %s",
-				__func__, sig, strbuf);
+		FATAL_SYSERROR(errno, "ignore_signal(%d)", sig);
 	}
 }
 
diff --git a/lib/isc/net.c b/lib/isc/net.c
index 4b84f2c072..89a57551fe 100644
--- a/lib/isc/net.c
+++ b/lib/isc/net.c
@@ -122,7 +122,6 @@ static isc_result_t
 try_proto(int domain) {
 	int s;
 	isc_result_t result = ISC_R_SUCCESS;
-	char strbuf[ISC_STRERRORSIZE];
 
 	s = socket(domain, SOCK_STREAM, 0);
 	if (s == -1) {
@@ -141,8 +140,7 @@ try_proto(int domain) {
 #endif /* ifdef EINVAL */
 			return (ISC_R_NOTFOUND);
 		default:
-			strerror_r(errno, strbuf, sizeof(strbuf));
-			UNEXPECTED_ERROR("socket() failed: %s", strbuf);
+			UNEXPECTED_SYSERROR(errno, "socket()");
 			return (ISC_R_UNEXPECTED);
 		}
 	}
@@ -222,7 +220,6 @@ static void
 try_ipv6only(void) {
 #ifdef IPV6_V6ONLY
 	int s, on;
-	char strbuf[ISC_STRERRORSIZE];
 #endif /* ifdef IPV6_V6ONLY */
 	isc_result_t result;
 
@@ -239,8 +236,7 @@ try_ipv6only(void) {
 	/* check for TCP sockets */
 	s = socket(PF_INET6, SOCK_STREAM, 0);
 	if (s == -1) {
-		strerror_r(errno, strbuf, sizeof(strbuf));
-		UNEXPECTED_ERROR("socket() failed: %s", strbuf);
+		UNEXPECTED_SYSERROR(errno, "socket()");
 		ipv6only_result = ISC_R_UNEXPECTED;
 		return;
 	}
@@ -256,8 +252,7 @@ try_ipv6only(void) {
 	/* check for UDP sockets */
 	s = socket(PF_INET6, SOCK_DGRAM, 0);
 	if (s == -1) {
-		strerror_r(errno, strbuf, sizeof(strbuf));
-		UNEXPECTED_ERROR("socket() failed: %s", strbuf);
+		UNEXPECTED_SYSERROR(errno, "socket()");
 		ipv6only_result = ISC_R_UNEXPECTED;
 		return;
 	}
@@ -285,7 +280,6 @@ initialize_ipv6only(void) {
 static void
 try_ipv6pktinfo(void) {
 	int s, on;
-	char strbuf[ISC_STRERRORSIZE];
 	isc_result_t result;
 	int optname;
 
@@ -298,8 +292,7 @@ try_ipv6pktinfo(void) {
 	/* we only use this for UDP sockets */
 	s = socket(PF_INET6, SOCK_DGRAM, IPPROTO_UDP);
 	if (s == -1) {
-		strerror_r(errno, strbuf, sizeof(strbuf));
-		UNEXPECTED_ERROR("socket() failed: %s", strbuf);
+		UNEXPECTED_SYSERROR(errno, "socket()");
 		ipv6pktinfo_result = ISC_R_UNEXPECTED;
 		return;
 	}
@@ -405,11 +398,10 @@ static isc_result_t
 make_nonblock(int fd) {
 	int ret;
 	int flags;
-	char strbuf[ISC_STRERRORSIZE];
-#ifdef USE_FIONBIO_IOCTL
-	int on = 1;
 
-	ret = ioctl(fd, FIONBIO, (char *)&on);
+#ifdef USE_FIONBIO_IOCTL
+	flags = 1;
+	ret = ioctl(fd, FIONBIO, (char *)&flags);
 #else  /* ifdef USE_FIONBIO_IOCTL */
 	flags = fcntl(fd, F_GETFL, 0);
 	flags |= O_NONBLOCK;
@@ -417,14 +409,11 @@ make_nonblock(int fd) {
 #endif /* ifdef USE_FIONBIO_IOCTL */
 
 	if (ret == -1) {
-		strerror_r(errno, strbuf, sizeof(strbuf));
 #ifdef USE_FIONBIO_IOCTL
-		UNEXPECTED_ERROR("ioctl(%d, FIONBIO, &on): %s", fd, strbuf);
-#else  /* ifdef USE_FIONBIO_IOCTL */
-		UNEXPECTED_ERROR("fcntl(%d, F_SETFL, %d): %s", fd, flags,
-				 strbuf);
-#endif /* ifdef USE_FIONBIO_IOCTL */
-
+		UNEXPECTED_SYSERROR(errno, "ioctl(%d, FIONBIO, &on)", fd);
+#else
+		UNEXPECTED_SYSERROR(errno, "fcntl(%d, F_SETFL, %d)", fd, flags);
+#endif
 		return (ISC_R_UNEXPECTED);
 	}
 
@@ -503,7 +492,6 @@ cmsgsend(int s, int level, int type, struct addrinfo *res) {
 	}
 
 	if (sendmsg(s, &msg, 0) < 0) {
-		int debug = ISC_LOG_DEBUG(10);
 		switch (errno) {
 #ifdef ENOPROTOOPT
 		case ENOPROTOOPT:
@@ -513,20 +501,17 @@ cmsgsend(int s, int level, int type, struct addrinfo *res) {
 #endif /* ifdef EOPNOTSUPP */
 		case EINVAL:
 		case EPERM:
-			break;
-		default:
-			debug = ISC_LOG_NOTICE;
-		}
-		strerror_r(errno, strbuf, sizeof(strbuf));
-		if (debug != ISC_LOG_NOTICE) {
+			strerror_r(errno, strbuf, sizeof(strbuf));
 			isc_log_write(isc_lctx, ISC_LOGCATEGORY_GENERAL,
 				      ISC_LOGMODULE_SOCKET, ISC_LOG_DEBUG(10),
 				      "sendmsg: %s", strbuf);
-		} else {
-			UNEXPECTED_ERROR(
-				"probing sendmsg() with %s=%02x failed: %s",
+			break;
+		default:
+			UNEXPECTED_SYSERROR(
+				errno, "probing sendmsg() with %s=%02x failed",
 				(type == IP_TOS) ? "IP_TOS" : "IPV6_TCLASS",
-				dscp, strbuf);
+				dscp);
+			break;
 		}
 		return (false);
 	}
@@ -586,7 +571,6 @@ try_dscp_v4(void) {
 	}
 
 	s = socket(res0->ai_family, res0->ai_socktype, res0->ai_protocol);
-
 	if (s == -1) {
 		strerror_r(errno, strbuf, sizeof(strbuf));
 		isc_log_write(isc_lctx, ISC_LOGCATEGORY_GENERAL,
diff --git a/lib/isc/netmgr/netmgr.c b/lib/isc/netmgr/netmgr.c
index ac9ba9b695..e33dbbc4ca 100644
--- a/lib/isc/netmgr/netmgr.c
+++ b/lib/isc/netmgr/netmgr.c
@@ -198,11 +198,10 @@ isc_netmgr_create(isc_mem_t *mctx, isc_loopmgr_t *loopmgr, isc_nm_t **netmgrp) {
 	isc_nm_t *netmgr = NULL;
 
 	if (uv_version() < MINIMAL_UV_VERSION) {
-		isc_error_fatal(__FILE__, __LINE__,
-				"libuv version too old: running with libuv %s "
-				"when compiled with libuv %s will lead to "
-				"libuv failures because of unknown flags",
-				uv_version_string(), UV_VERSION_STRING);
+		FATAL_ERROR("libuv version too old: running with libuv %s "
+			    "when compiled with libuv %s will lead to "
+			    "libuv failures because of unknown flags",
+			    uv_version_string(), UV_VERSION_STRING);
 	}
 
 	netmgr = isc_mem_get(mctx, sizeof(*netmgr));
diff --git a/lib/isc/stdtime.c b/lib/isc/stdtime.c
index ada19d0ef5..086c0c775b 100644
--- a/lib/isc/stdtime.c
+++ b/lib/isc/stdtime.c
@@ -41,10 +41,7 @@ isc_stdtime_get(isc_stdtime_t *t) {
 	struct timespec ts;
 
 	if (clock_gettime(CLOCKSOURCE, &ts) == -1) {
-		char strbuf[ISC_STRERRORSIZE];
-		strerror_r(errno, strbuf, sizeof(strbuf));
-		isc_error_fatal(__FILE__, __LINE__, "clock_gettime failed: %s",
-				strbuf);
+		FATAL_SYSERROR(errno, "clock_gettime()");
 	}
 
 	REQUIRE(ts.tv_sec > 0 && ts.tv_nsec >= 0 && ts.tv_nsec < NS_PER_S);
diff --git a/lib/isc/time.c b/lib/isc/time.c
index 4c01132adb..8570a9439a 100644
--- a/lib/isc/time.c
+++ b/lib/isc/time.c
@@ -92,9 +92,7 @@ time_now(isc_time_t *t, clockid_t clock) {
 	REQUIRE(t != NULL);
 
 	if (clock_gettime(clock, &ts) == -1) {
-		char strbuf[ISC_STRERRORSIZE];
-		strerror_r(errno, strbuf, sizeof(strbuf));
-		UNEXPECTED_ERROR("%s", strbuf);
+		UNEXPECTED_SYSERROR(errno, "clock_gettime()");
 		return (ISC_R_UNEXPECTED);
 	}
 
@@ -136,9 +134,7 @@ isc_time_nowplusinterval(isc_time_t *t, const isc_interval_t *i) {
 	INSIST(i->nanoseconds < NS_PER_S);
 
 	if (clock_gettime(CLOCKSOURCE, &ts) == -1) {
-		char strbuf[ISC_STRERRORSIZE];
-		strerror_r(errno, strbuf, sizeof(strbuf));
-		UNEXPECTED_ERROR("%s", strbuf);
+		UNEXPECTED_SYSERROR(errno, "clock_gettime()");
 		return (ISC_R_UNEXPECTED);
 	}