diff --git a/clients/upsimage.c b/clients/upsimage.c
index 9e92f96e8e..2739929c83 100644
--- a/clients/upsimage.c
+++ b/clients/upsimage.c
@@ -210,6 +210,17 @@ static void drawscale(
 }
 
 /* draws the bar style indicator */
+static void drawbar(
+	int lvllo, int lvlhi,			/* min and max numbers on the scale */
+	int step, int step5, int step10,	/* steps for minor, submajor and major dashes */
+	int redlo1, int redhi1,			/* first red zone start and end */
+	int redlo2, int redhi2,			/* second red zone start and end */
+	int grnlo, int grnhi,			/* green zone start and end */
+	double value, 				/* UPS variable value to draw */
+	const char *format			/* printf style format to be used when rendering summary text */
+)
+	__attribute__((noreturn));
+
 static void drawbar(
 	int lvllo, int lvlhi,			/* min and max numbers on the scale */
 	int step, int step5, int step10,	/* steps for minor, submajor and major dashes */
@@ -284,6 +295,9 @@ static void drawbar(
 }
 
 /* draws the error image */
+static void noimage(const char *fmt, ...)
+	__attribute__((noreturn));
+
 static void noimage(const char *fmt, ...)
 {
 	gdImagePtr	im;
@@ -331,6 +345,12 @@ static void noimage(const char *fmt, ...)
 
 	drawimage(im);
 
+	/* NOTE: Earlier code called noimage() and then exit(EXIT_FAILURE);
+	 * to signal an error via process exit code. Now that drawimage()
+	 * always ends with exit(EXIT_SUCCESS) - which might make webserver
+	 * feel good - the command-line use if any suffers no error returns.
+	 */
+
 	/* NOTREACHED */
 }
 
@@ -338,6 +358,10 @@ static void noimage(const char *fmt, ...)
    UPS variable can be determined.
    deviation < 0 means that values below nom should be grey instead of
    green */
+static void drawgeneralbar(double var, int min, int nom, int max,
+		int deviation, 	const char *format)
+	__attribute__((noreturn));
+
 static void drawgeneralbar(double var, int min, int nom, int max,
 		int deviation, 	const char *format)
 {
@@ -397,6 +421,10 @@ static void drawgeneralbar(double var, int min, int nom, int max,
 }
 
 /* draws input and output voltage bar style indicators */
+static void draw_utility(double var, int min, int nom, int max,
+		int deviation, const char *format)
+	__attribute__((noreturn));
+
 static void draw_utility(double var, int min, int nom, int max,
 		int deviation, const char *format)
 {
@@ -440,6 +468,10 @@ static void draw_utility(double var, int min, int nom, int max,
 }
 
 /* draws battery.percent bar style indicator */
+static void draw_battpct(double var, int min, int nom,
+		int max, int deviation, const char *format)
+	__attribute__((noreturn));
+
 static void draw_battpct(double var, int min, int nom,
 		int max, int deviation, const char *format)
 {
@@ -455,6 +487,10 @@ static void draw_battpct(double var, int min, int nom,
 }
 
 /* draws battery.voltage bar style indicator */
+static void draw_battvolt(double var, int min, int nom, int max,
+		int deviation, const char *format)
+	__attribute__((noreturn));
+
 static void draw_battvolt(double var, int min, int nom, int max,
 		int deviation, const char *format)
 {
@@ -501,6 +537,11 @@ static void draw_battvolt(double var, int min, int nom, int max,
 }
 
 /* draws ups.load bar style indicator */
+static void draw_upsload(double var, int min,
+		int nom, int max,
+		int deviation, const char *format)
+	__attribute__((noreturn));
+
 static void draw_upsload(double var, int min,
 		int nom, int max,
 		int deviation, const char *format)
@@ -514,6 +555,10 @@ static void draw_upsload(double var, int min,
 }
 
 /* draws temperature bar style indicator */
+static void draw_temperature(double var, int min, int nom, int max,
+		int deviation, const char *format)
+	__attribute__((noreturn));
+
 static void draw_temperature(double var, int min, int nom, int max,
 		int deviation, const char *format)
 {
@@ -526,6 +571,10 @@ static void draw_temperature(double var, int min, int nom, int max,
 }
 
 /* draws humidity bar style indicator */
+static void draw_humidity(double var, int min, int nom, int max,
+		int deviation, const char *format)
+	__attribute__((noreturn));
+
 static void draw_humidity(double var, int min, int nom, int max,
 		int deviation, const char *format)
 {
@@ -581,13 +630,17 @@ int main(int argc, char **argv)
 
 	if (upscli_splitname(monhost, &upsname, &hostname, &port) != 0) {
 		noimage("Invalid UPS definition (upsname[@hostname[:port]])\n");
-		exit(EXIT_FAILURE);
+#ifndef HAVE___ATTRIBUTE__NORETURN
+		exit(EXIT_FAILURE);	/* Should not get here in practice, but compiler is afraid we can fall through */
+#endif
 	}
 
 	if (upscli_connect(&ups, hostname, port, 0) < 0) {
 		noimage("Can't connect to server:\n%s\n",
 			upscli_strerror(&ups));
-		exit(EXIT_FAILURE);
+#ifndef HAVE___ATTRIBUTE__NORETURN
+		exit(EXIT_FAILURE);	/* Should not get here in practice, but compiler is afraid we can fall through */
+#endif
 	}
 
 	for (i = 0; imgvar[i].name; i++)
@@ -597,7 +650,9 @@ int main(int argc, char **argv)
 			   registered with this variable */
 			if (!imgvar[i].drawfunc) {
 				noimage("Draw function N/A");
-				exit(EXIT_FAILURE);
+#ifndef HAVE___ATTRIBUTE__NORETURN
+				exit(EXIT_FAILURE);	/* Should not get here in practice, but compiler is afraid we can fall through */
+#endif
 			}
 
 			/* get the variable value */
@@ -608,7 +663,9 @@ int main(int argc, char **argv)
 				snprintf(str, sizeof(str), "%s N/A",
 					imgvar[i].name);
 				noimage(str);
-				exit(EXIT_FAILURE);
+#ifndef HAVE___ATTRIBUTE__NORETURN
+				exit(EXIT_FAILURE);	/* Should not get here in practice, but compiler is afraid we can fall through */
+#endif
 			}
 
 			/* when getting minimum, nominal and maximum values,
@@ -661,7 +718,9 @@ int main(int argc, char **argv)
 		}
 
 	noimage("Unknown display");
+#ifndef HAVE___ATTRIBUTE__NORETURN
 	exit(EXIT_FAILURE);
+#endif
 }
 
 imgvar_t imgvar[] = {
diff --git a/clients/upsmon.c b/clients/upsmon.c
index 0f769385a6..e76fb16354 100644
--- a/clients/upsmon.c
+++ b/clients/upsmon.c
@@ -630,6 +630,9 @@ static void slavesync(void)
 	}
 }
 
+static void forceshutdown(void)
+	__attribute__((noreturn));
+
 static void forceshutdown(void)
 {
 	utype_t	*ups;
diff --git a/common/common.c b/common/common.c
index b51e1f5ee7..d9985dd387 100644
--- a/common/common.c
+++ b/common/common.c
@@ -21,6 +21,7 @@
 
 #include <ctype.h>
 #include <syslog.h>
+#include <errno.h>
 #include <pwd.h>
 #include <grp.h>
 #include <dirent.h>
@@ -301,7 +302,11 @@ int snprintfcat(char *dst, size_t size, const char *fmt, ...)
 	int ret;
 
 	size--;
-	assert(len <= size);
+	if (len > size) {
+		/* Do not truncate existing string */
+		errno = ERANGE;
+		return -1;
+	}
 
 	va_start(ap, fmt);
 #ifdef HAVE_PRAGMAS_FOR_GCC_DIAGNOSTIC_IGNORED_FORMAT_NONLITERAL
@@ -327,9 +332,14 @@ int snprintfcat(char *dst, size_t size, const char *fmt, ...)
 	 * In theory it can overflow a 64-vs-32 bit range, or signed-vs-unsigned.
 	 * In practice we hope to not have gigabytes-long config strings.
 	 */
-	assert(ret >= 0);
+	if (ret < 0) {
+		return ret;
+	}
 #ifdef INT_MAX
-	assert ((unsigned long long)len < ((unsigned long long)INT_MAX - ret));
+	if ( ( (unsigned long long)len + (unsigned long long)ret ) >= (unsigned long long)INT_MAX ) {
+		errno = ERANGE;
+		return -1;
+	}
 #endif
 	return (int)len + ret;
 }
diff --git a/common/str.c b/common/str.c
index 092efcf427..8b58495583 100644
--- a/common/str.c
+++ b/common/str.c
@@ -252,7 +252,7 @@ int	str_to_short(const char *string, short *number, const int base)
 		return 0;
 	}
 
-	*number = num;
+	*number = (short)num;
 	return 1;
 }
 
@@ -273,7 +273,7 @@ int	str_to_short_strict(const char *string, short *number, const int base)
 		return 0;
 	}
 
-	*number = num;
+	*number = (short)num;
 	return 1;
 }
 
@@ -291,7 +291,7 @@ int	str_to_ushort(const char *string, unsigned short *number, const int base)
 		return 0;
 	}
 
-	*number = num;
+	*number = (unsigned short)num;
 	return 1;
 }
 
@@ -309,7 +309,7 @@ int	str_to_ushort_strict(const char *string, unsigned short *number, const int b
 		return 0;
 	}
 
-	*number = num;
+	*number = (unsigned short)num;
 	return 1;
 }
 
diff --git a/common/strerror.c b/common/strerror.c
index b5cecb9673..e00f208aba 100644
--- a/common/strerror.c
+++ b/common/strerror.c
@@ -11,6 +11,16 @@ char *strerror(int errnum)
 {
     static char buf[32];
 
+#ifdef HAVE_PRAGMAS_FOR_GCC_DIAGNOSTIC_IGNORED_UNREACHABLE_CODE
+#pragma GCC diagnostic push
+#endif
+#ifdef HAVE_PRAGMA_GCC_DIAGNOSTIC_IGNORED_UNREACHABLE_CODE_BREAK
+#pragma GCC diagnostic ignored "-Wunreachable-code-break"
+#endif
+#ifdef HAVE_PRAGMA_GCC_DIAGNOSTIC_IGNORED_UNREACHABLE_CODE
+#pragma GCC diagnostic ignored "-Wunreachable-code"
+#endif
+
     switch (errnum) {
 #if defined (EPERM)
       case EPERM:
@@ -498,6 +508,11 @@ char *strerror(int errnum)
     /* Fallback: just print the error number */
     snprintf(buf, sizeof(buf), "Error %d", errnum);
     return buf;
+
+#ifdef HAVE_PRAGMAS_FOR_GCC_DIAGNOSTIC_IGNORED_UNREACHABLE_CODE
+#pragma GCC diagnostic pop
+#endif
+
 }
 
 #endif /* HAVE_STRERROR */
diff --git a/common/upsconf.c b/common/upsconf.c
index 80c2de091c..9c6ebbd1f4 100644
--- a/common/upsconf.c
+++ b/common/upsconf.c
@@ -29,7 +29,7 @@
 	static	char	*ups_section;
 
 /* handle arguments separated by parseconf */
-static void conf_args(int numargs, char **arg)
+static void conf_args(size_t numargs, char **arg)
 {
 	if (numargs < 1)
 		return;
diff --git a/drivers/al175.c b/drivers/al175.c
index a705a42542..a617b919eb 100644
--- a/drivers/al175.c
+++ b/drivers/al175.c
@@ -191,7 +191,7 @@ typedef struct {
 /**
  * convert hex string to int
  * @param  head  input string
- * @param  count string length
+ * @param  len   string length
  * @return parsed value (>=0) if success, -1 on error
  */
 static long from_hex(const byte_t *head, unsigned len)
@@ -1000,23 +1000,23 @@ typedef int VV_t;	/* voltage */
 #define	ACT int
 
 /* Declare to keep compiler happy even if some routines below are not used currently */
-ACT	TOGGLE_PRS_ONOFF	();
-ACT	CANCEL_BOOST		();
-ACT	STOP_BATTERY_TEST	();
+ACT	TOGGLE_PRS_ONOFF	(void);
+ACT	CANCEL_BOOST		(void);
+ACT	STOP_BATTERY_TEST	(void);
 ACT	START_BATTERY_TEST	(VV_t EndVolt, unsigned Minutes);
 ACT	SET_FLOAT_VOLTAGE	(VV_t v);
 ACT	SET_BOOST_VOLTAGE	(VV_t v);
 ACT	SET_HIGH_BATTERY_LIMIT	(VV_t Vhigh);
 ACT	SET_LOW_BATTERY_LIMIT	(VV_t Vlow);
 ACT	SET_DISCONNECT_LEVEL_AND_DELAY	(VV_t level, mm_t delay);
-ACT	RESET_ALARMS		();
-ACT	CHANGE_COMM_PROTOCOL	();
+ACT	RESET_ALARMS		(void);
+ACT	CHANGE_COMM_PROTOCOL	(void);
 ACT	SET_VOLTAGE_AT_ZERO_T	(VV_t v);
 ACT	SET_SLOPE_AT_ZERO_T	(VV_t mv_per_degree);
 ACT	SET_MAX_TCOMP_VOLTAGE	(VV_t v);
 ACT	SET_MIN_TCOMP_VOLTAGE	(VV_t v);
 ACT	SWITCH_TEMP_COMP	(int on);
-ACT	SWITCH_SYM_ALARM	();
+ACT	SWITCH_SYM_ALARM	(void);
 
 /* Implement */
 ACT	TOGGLE_PRS_ONOFF	()		{ return al175_do(0x81, 0x80			Z3);	}
@@ -1229,6 +1229,9 @@ void upsdrv_updateinfo(void)
 
 }
 
+void upsdrv_shutdown(void)
+	__attribute__((noreturn));
+
 void upsdrv_shutdown(void)
 {
 	/* TODO use TOGGLE_PRS_ONOFF for shutdown */
diff --git a/drivers/bcmxcp.c b/drivers/bcmxcp.c
index cb1aa5ceaa..d52b6bf54b 100644
--- a/drivers/bcmxcp.c
+++ b/drivers/bcmxcp.c
@@ -2076,9 +2076,6 @@ static int instcmd(const char *cmdname, const char *extra)
 		snprintf(success_msg, sizeof(success_msg)-1, "Outlet %d is  %s",outlet_num, (cmdname[NUT_OUTLET_POSITION+8] == 'n')?"On":"Off");
 
 		return decode_instcmd_exec(res, (unsigned char)answer[0], cmdname, success_msg);
-
-
-
 	}
 
 	upslogx(LOG_NOTICE, "instcmd: unknown command [%s]", cmdname);
@@ -2099,39 +2096,32 @@ static int decode_instcmd_exec(const int res, const unsigned char exec_status, c
 			upslogx(LOG_NOTICE, "[%s] %s", cmdname, success_msg);
 			upsdrv_comm_good();
 			return STAT_INSTCMD_HANDLED;
-			break;
 			}
 		case BCMXCP_RETURN_ACCEPTED_PARAMETER_ADJUST: {
 			upslogx(LOG_NOTICE, "[%s] Parameter adjusted", cmdname);
 			upslogx(LOG_NOTICE, "[%s] %s", cmdname, success_msg);
 			upsdrv_comm_good();
 			return STAT_INSTCMD_HANDLED;
-			break;
 			}
 		case BCMXCP_RETURN_BUSY: {
 			upslogx(LOG_NOTICE, "[%s] Busy or disbled by front panel", cmdname);
 			return STAT_INSTCMD_FAILED;
-			break;
 			}
 		case BCMXCP_RETURN_UNRECOGNISED: {
 			upslogx(LOG_NOTICE, "[%s] Unrecognised command byte or corrupt checksum", cmdname);
 			return STAT_INSTCMD_FAILED;
-			break;
 			}
 		case BCMXCP_RETURN_INVALID_PARAMETER: {
 			upslogx(LOG_NOTICE, "[%s] Invalid parameter", cmdname);
 			return STAT_INSTCMD_INVALID;
-			break;
 			}
 		case BCMXCP_RETURN_PARAMETER_OUT_OF_RANGE: {
 			upslogx(LOG_NOTICE, "[%s] Parameter out of range", cmdname);
 			return STAT_INSTCMD_INVALID;
-			break;
 			}
 		default: {
 			upslogx(LOG_NOTICE, "[%s] Not supported", cmdname);
 			return STAT_INSTCMD_INVALID;
-			break;
 			}
 	}
 }
@@ -2442,39 +2432,32 @@ static int decode_setvar_exec(const int res, const unsigned char exec_status, co
 			upslogx(LOG_NOTICE, "[%s] %s", cmdname, success_msg);
 			upsdrv_comm_good();
 			return STAT_SET_HANDLED;
-			break;
 			}
 		case BCMXCP_RETURN_ACCEPTED_PARAMETER_ADJUST: {
 			upslogx(LOG_NOTICE, "[%s] Parameter adjusted", cmdname);
 			upslogx(LOG_NOTICE, "[%s] %s", cmdname, success_msg);
 			upsdrv_comm_good();
 			return STAT_SET_HANDLED;
-			break;
 			}
 		case BCMXCP_RETURN_BUSY: {
 			upslogx(LOG_NOTICE, "[%s] Busy or disbled by front panel", cmdname);
 			return STAT_SET_FAILED;
-			break;
 			}
 		case BCMXCP_RETURN_UNRECOGNISED: {
 			upslogx(LOG_NOTICE, "[%s] Unrecognised command byte or corrupt checksum", cmdname);
 			return STAT_SET_FAILED;
-			break;
 			}
 		case BCMXCP_RETURN_INVALID_PARAMETER: {
 			upslogx(LOG_NOTICE, "[%s] Invalid parameter", cmdname);
 			return STAT_SET_INVALID;
-			break;
 			}
 		case BCMXCP_RETURN_PARAMETER_OUT_OF_RANGE: {
 			upslogx(LOG_NOTICE, "[%s] Parameter out of range", cmdname);
 			return STAT_SET_INVALID;
-			break;
 			}
 		default: {
 			upslogx(LOG_NOTICE, "[%s] Not supported", cmdname);
 			return STAT_SET_INVALID;
-			break;
 			}
 	}
 }
diff --git a/drivers/bestfcom.c b/drivers/bestfcom.c
index c19f727045..35e28a3c7e 100644
--- a/drivers/bestfcom.c
+++ b/drivers/bestfcom.c
@@ -637,7 +637,6 @@ static void upsdrv_init_nofc(void)
 			break;
 		default:
 			fatalx(EXIT_FAILURE, "Unknown model %s in upsdrv_init_nofc()", rstring);
-			break;
 	}
 	fc.valid = 1;
 }
diff --git a/drivers/hidparser.c b/drivers/hidparser.c
index c6f124ca02..ca36927098 100644
--- a/drivers/hidparser.c
+++ b/drivers/hidparser.c
@@ -157,7 +157,7 @@ static int HIDParse(HIDParser_t *pParser, HIDData_t *pData)
 		if (pParser->Count == 0) {
 			pParser->Item = pParser->ReportDesc[pParser->Pos++];
 			pParser->Value = 0;
-#if WORDS_BIGENDIAN
+#if (defined (WORDS_BIGENDIAN)) && (WORDS_BIGENDIAN)
 			{
 				int	i;
 				unsigned long	valTmp = 0;
diff --git a/drivers/libshut.c b/drivers/libshut.c
index 65ffd5f568..c723466771 100644
--- a/drivers/libshut.c
+++ b/drivers/libshut.c
@@ -274,7 +274,7 @@ static int shut_control_msg(int upsfd, int requesttype, int request, int value,
 #define BYTESWAP(in) (((in & 0xFF) << 8) + ((in & 0xFF00) >> 8))
 static void align_request(struct shut_ctrltransfer_s *ctrl)
 {
-#if WORDS_BIGENDIAN
+#if (defined (WORDS_BIGENDIAN)) && (WORDS_BIGENDIAN)
 	/* Sparc/Mips/... are big endian, USB/SHUT little endian */
 	(*ctrl).wValue    = BYTESWAP((*ctrl).wValue);
 	(*ctrl).wIndex    = BYTESWAP((*ctrl).wIndex);
diff --git a/drivers/liebert-esp2.c b/drivers/liebert-esp2.c
index e415332e4c..f246ffe322 100644
--- a/drivers/liebert-esp2.c
+++ b/drivers/liebert-esp2.c
@@ -553,10 +553,10 @@ void upsdrv_shutdown(void)
 	char reply[8];
 
 	if(!(do_command(cmd_setOutOffMode, reply, 8) != -1) &&
-	(do_command(cmd_setOutOffDelay, reply, 8) != -1) &&
-	(do_command(cmd_sysLoadKey, reply, 6) != -1) &&
-	(do_command(cmd_shutdown, reply, 8) != -1))
-	upslogx(LOG_ERR, "Failed to shutdown UPS");
+	    (do_command(cmd_setOutOffDelay, reply, 8) != -1) &&
+	    (do_command(cmd_sysLoadKey, reply, 6) != -1) &&
+	    (do_command(cmd_shutdown, reply, 8) != -1))
+			upslogx(LOG_ERR, "Failed to shutdown UPS");
 }
 
 static int instcmd(const char *cmdname, const char *extra)
diff --git a/drivers/netxml-ups.c b/drivers/netxml-ups.c
index e6563e4d8e..025c0e1518 100644
--- a/drivers/netxml-ups.c
+++ b/drivers/netxml-ups.c
@@ -175,7 +175,7 @@ static object_entry_t *set_object_add(
 /**
  *  \brief  SET_OBJECT: RAW POST mode implementation
  *
- *  \brief  req  SET_OBJECT request
+ *  \param  req  SET_OBJECT request
  *
  *  \return Response to the request
  */
@@ -185,7 +185,7 @@ static object_query_t *set_object_raw(object_query_t *req);
 /**
  *  \brief  SET_OBJECT: FORM POST mode implementation
  *
- *  \brief  req  SET_OBJECT request
+ *  \param  req  SET_OBJECT request
  *
  *  \return \c NULL (FORM POST mode resp. is ignored by specification)
  */
@@ -195,7 +195,7 @@ static object_query_t *set_object_form(object_query_t *req);
 /**
  *  \brief  SET_OBJECT: implementation
  *
- *  \brief  req  SET_OBJECT request
+ *  \param  req  SET_OBJECT request
  *
  *  \return Response to the request
  */
@@ -799,8 +799,8 @@ static int netxml_alarm_subscribe(const char *page)
 		}
 
 		/* Range of valid values constrained above */
-		port = tmp_port;
-		secret = tmp_secret;
+		port = (int)tmp_port;
+		secret = (int)tmp_secret;
 
 	}
 
@@ -1069,7 +1069,7 @@ static void set_object_req_destroy(set_object_req_t *req) {
 /**
  *  \brief  SET_OBJECT response list entry destructor
  *
- *  \param  req  SET_OBJECT response list entry
+ *  \param  resp  SET_OBJECT response list entry
  */
 static void set_object_resp_destroy(set_object_resp_t *resp) {
 	assert(NULL != resp);
@@ -1238,8 +1238,8 @@ static object_entry_t *set_object_add(
  *  \param  buff   Buffer
  *  \param  entry  SET_OBJECT request entry
  *
- *  \retval OBJECT_OK    on success
- *  \retval OBJECT_ERROR otherwise
+ *  \return OBJECT_OK    on success
+ *  \return OBJECT_ERROR otherwise
  */
 static object_query_status_t set_object_serialise_entries(ne_buffer *buff, object_entry_t *entry) {
 	object_query_status_t status = OBJECT_OK;
@@ -1580,9 +1580,9 @@ static object_query_t *set_object_deserialise_raw(ne_buffer *buff) {
  *
  *  The function creates HTTP request, sends it and reads-out the response.
  *
- *  \param[in]   session    HTTP session
+ *  \param[in]   argsession HTTP session
  *  \param[in]   method     Request method
- *  \param[in]   uri        Request URI
+ *  \param[in]   arguri     Request URI
  *  \param[in]   ct         Request content type (optional, \c NULL accepted)
  *  \param[in]   req_body   Request body (optional, \c NULL is accepted)
  *  \param[out]  resp_body  Response body (optional, \c NULL is accepted)
diff --git a/drivers/nutdrv_qx.c b/drivers/nutdrv_qx.c
index 0388fd20f4..652d1167ca 100644
--- a/drivers/nutdrv_qx.c
+++ b/drivers/nutdrv_qx.c
@@ -2149,11 +2149,29 @@ static int	qx_command(const char *cmd, char *buf, size_t buflen)
 		{
 		case -EBUSY:		/* Device or resource busy */
 			fatal_with_errno(EXIT_FAILURE, "Got disconnected by another driver");
+#ifndef HAVE___ATTRIBUTE__NORETURN
+# if (defined HAVE_PRAGMA_GCC_DIAGNOSTIC_PUSH_POP) && (defined HAVE_PRAGMA_GCC_DIAGNOSTIC_IGNORED_UNREACHABLE_CODE)
+#  pragma GCC diagnostic push
+#  pragma GCC diagnostic ignored "-Wunreachable-code"
+# endif
 			exit(EXIT_FAILURE);	/* Should not get here in practice, but compiler is afraid we can fall through */
+# if (defined HAVE_PRAGMA_GCC_DIAGNOSTIC_PUSH_POP) && (defined HAVE_PRAGMA_GCC_DIAGNOSTIC_IGNORED_UNREACHABLE_CODE)
+#  pragma GCC diagnostic pop
+# endif
+#endif
 
 		case -EPERM:		/* Operation not permitted */
 			fatal_with_errno(EXIT_FAILURE, "Permissions problem");
+#ifndef HAVE___ATTRIBUTE__NORETURN
+# if (defined HAVE_PRAGMA_GCC_DIAGNOSTIC_PUSH_POP) && (defined HAVE_PRAGMA_GCC_DIAGNOSTIC_IGNORED_UNREACHABLE_CODE)
+#  pragma GCC diagnostic push
+#  pragma GCC diagnostic ignored "-Wunreachable-code"
+# endif
 			exit(EXIT_FAILURE);	/* Should not get here in practice, but compiler is afraid we can fall through */
+# if (defined HAVE_PRAGMA_GCC_DIAGNOSTIC_PUSH_POP) && (defined HAVE_PRAGMA_GCC_DIAGNOSTIC_IGNORED_UNREACHABLE_CODE)
+#  pragma GCC diagnostic pop
+# endif
+#endif
 
 		case -EPIPE:		/* Broken pipe */
 			if (usb_clear_halt(udev, 0x81) == 0) {
diff --git a/drivers/powercom.c b/drivers/powercom.c
index 23e2a09077..22182f4236 100644
--- a/drivers/powercom.c
+++ b/drivers/powercom.c
@@ -284,6 +284,9 @@ static unsigned int OPTImodels[]	= {0,0,0,575,0,0,0,0,0,0,0,0,0,0,0,0};
  * local used functions
  */
 
+static void shutdown_halt(void)
+	__attribute__((noreturn));
+
 static void shutdown_halt(void)
 {
 	ser_send_char (upsfd, SHUTDOWN);
@@ -294,6 +297,9 @@ static void shutdown_halt(void)
 	exit (0);
 }
 
+static void shutdown_ret(void)
+	__attribute__((noreturn));
+
 static void shutdown_ret(void)
 {
 	ser_send_char (upsfd, RESTART);
@@ -314,12 +320,19 @@ static int instcmd (const char *cmdname, const char *extra)
 	    return STAT_INSTCMD_HANDLED;
 	}
 	if (!strcasecmp(cmdname, "shutdown.return")) {
+		/* NOTE: In this context, "return" is UPS behavior after the
+		 * wall-power gets restored. The routine exits the driver anyway.
+		 */
 		shutdown_ret();
+#ifndef HAVE___ATTRIBUTE__NORETURN
 		return STAT_INSTCMD_HANDLED;
+#endif
 	}
 	if (!strcasecmp(cmdname, "shutdown.stayoff")) {
 		shutdown_halt();
+#ifndef HAVE___ATTRIBUTE__NORETURN
 		return STAT_INSTCMD_HANDLED;
+#endif
 	}
 
 	upslogx(LOG_NOTICE, "instcmd: unknown command [%s] [%s]", cmdname, extra);
@@ -818,6 +831,9 @@ void upsdrv_updateinfo(void)
 }
 
 /* shutdown UPS */
+void upsdrv_shutdown(void)
+	__attribute__((noreturn));
+
 void upsdrv_shutdown(void)
 {
 	/* power down the attached load immediately */
diff --git a/drivers/powerman-pdu.c b/drivers/powerman-pdu.c
index de66fecb15..1611d3ce5b 100644
--- a/drivers/powerman-pdu.c
+++ b/drivers/powerman-pdu.c
@@ -133,6 +133,9 @@ void upsdrv_initinfo(void)
 	/* FIXME: no need for setvar (ex for outlet.n.delay.*)!? */
 }
 
+void upsdrv_shutdown(void)
+	__attribute__((noreturn));
+
 void upsdrv_shutdown(void)
 {
 	/* FIXME: shutdown all outlets? */
diff --git a/drivers/riello_usb.c b/drivers/riello_usb.c
index 1731b2a4fd..e353d097a1 100644
--- a/drivers/riello_usb.c
+++ b/drivers/riello_usb.c
@@ -952,6 +952,9 @@ void upsdrv_initinfo(void)
 	upsh.instcmd = riello_instcmd;
 }
 
+void upsdrv_shutdown(void)
+	__attribute__((noreturn));
+
 void upsdrv_shutdown(void)
 {
 	/* tell the UPS to shut down, then return - DO NOT SLEEP HERE */
diff --git a/tools/nut-scanner/scan_snmp.c b/tools/nut-scanner/scan_snmp.c
index f661110282..1dd730e913 100644
--- a/tools/nut-scanner/scan_snmp.c
+++ b/tools/nut-scanner/scan_snmp.c
@@ -99,11 +99,11 @@ static int (*nut_generate_Ku)(const oid * hashtype, u_int hashtype_len,
 			unsigned char * P, size_t pplen, unsigned char * Ku, size_t * kulen);
 static char* (*nut_snmp_out_toggle_options)(char *options);
 static const char * (*nut_snmp_api_errstring) (int snmp_errnumber);
-static int (*nut_snmp_errno);
-static oid (*nut_usmAESPrivProtocol);
-static oid (*nut_usmHMACMD5AuthProtocol);
-static oid (*nut_usmHMACSHA1AuthProtocol);
-static oid (*nut_usmDESPrivProtocol);
+static int *nut_snmp_errno;
+static oid *nut_usmAESPrivProtocol;
+static oid *nut_usmHMACMD5AuthProtocol;
+static oid *nut_usmHMACSHA1AuthProtocol;
+static oid *nut_usmDESPrivProtocol;
 
 /* return 0 on error; visible externally */
 int nutscan_load_snmp_library(const char *libname_path);