diff --git a/src/modules/ekf_att_pos_estimator/ekf_att_pos_estimator_main.cpp b/src/modules/ekf_att_pos_estimator/ekf_att_pos_estimator_main.cpp
index e1446bbe9b..ecd67ecf7a 100644
--- a/src/modules/ekf_att_pos_estimator/ekf_att_pos_estimator_main.cpp
+++ b/src/modules/ekf_att_pos_estimator/ekf_att_pos_estimator_main.cpp
@@ -44,6 +44,7 @@
 #include "estimator_22states.h"
 
 #include <px4_config.h>
+#include <px4_tasks.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
@@ -281,7 +282,7 @@ AttitudePositionEstimatorEKF::~AttitudePositionEstimatorEKF()
 
 			/* if we have given up, kill it */
 			if (++i > 50) {
-				task_delete(_estimator_task);
+				px4_task_delete(_estimator_task);
 				break;
 			}
 		} while (_estimator_task != -1);
@@ -490,7 +491,8 @@ void AttitudePositionEstimatorEKF::task_main()
 	_filter_start_time = hrt_absolute_time();
 
 	if (!_ekf) {
-		errx(1, "OUT OF MEM!");
+		warnx("OUT OF MEM!");
+		return;
 	}
 
 	/*
@@ -696,10 +698,8 @@ void AttitudePositionEstimatorEKF::task_main()
 
 	_task_running = false;
 
-	warnx("exiting.\n");
-
 	_estimator_task = -1;
-	_exit(0);
+	return;
 }
 
 void AttitudePositionEstimatorEKF::initializeGPS()
@@ -1039,7 +1039,7 @@ int AttitudePositionEstimatorEKF::start()
 					 SCHED_DEFAULT,
 					 SCHED_PRIORITY_MAX - 40,
 					 7500,
-					 (main_t)&AttitudePositionEstimatorEKF::task_main_trampoline,
+					 (px4_main_t)&AttitudePositionEstimatorEKF::task_main_trampoline,
 					 nullptr);
 
 	if (_estimator_task < 0) {
@@ -1155,7 +1155,7 @@ void AttitudePositionEstimatorEKF::pollData()
 	float deltaT = (_sensor_combined.timestamp - _last_run) / 1e6f;
 
 	/* guard against too large deltaT's */
-	if (!isfinite(deltaT) || deltaT > 1.0f || deltaT < 0.000001f) {
+	if (!std::isfinite(deltaT) || deltaT > 1.0f || deltaT < 0.000001f) {
 		deltaT = 0.01f;
 	}
 
@@ -1167,9 +1167,9 @@ void AttitudePositionEstimatorEKF::pollData()
 
 	int last_gyro_main = _gyro_main;
 
-	if (isfinite(_sensor_combined.gyro_rad_s[0]) &&
-	    isfinite(_sensor_combined.gyro_rad_s[1]) &&
-	    isfinite(_sensor_combined.gyro_rad_s[2]) &&
+	if (std::isfinite(_sensor_combined.gyro_rad_s[0]) &&
+	    std::isfinite(_sensor_combined.gyro_rad_s[1]) &&
+	    std::isfinite(_sensor_combined.gyro_rad_s[2]) &&
 	    (_sensor_combined.gyro_errcount <= _sensor_combined.gyro1_errcount)) {
 
 		_ekf->angRate.x = _sensor_combined.gyro_rad_s[0];
@@ -1178,9 +1178,9 @@ void AttitudePositionEstimatorEKF::pollData()
 		_gyro_main = 0;
 		_gyro_valid = true;
 
-	} else if (isfinite(_sensor_combined.gyro1_rad_s[0]) &&
-		   isfinite(_sensor_combined.gyro1_rad_s[1]) &&
-		   isfinite(_sensor_combined.gyro1_rad_s[2])) {
+	} else if (std::isfinite(_sensor_combined.gyro1_rad_s[0]) &&
+		   std::isfinite(_sensor_combined.gyro1_rad_s[1]) &&
+		   std::isfinite(_sensor_combined.gyro1_rad_s[2])) {
 
 		_ekf->angRate.x = _sensor_combined.gyro1_rad_s[0];
 		_ekf->angRate.y = _sensor_combined.gyro1_rad_s[1];
@@ -1528,25 +1528,29 @@ int AttitudePositionEstimatorEKF::trip_nan()
 int ekf_att_pos_estimator_main(int argc, char *argv[])
 {
 	if (argc < 2) {
-		errx(1, "usage: ekf_att_pos_estimator {start|stop|status|logging}");
+		warnx("usage: ekf_att_pos_estimator {start|stop|status|logging}");
+		return 1;
 	}
 
 	if (!strcmp(argv[1], "start")) {
 
 		if (estimator::g_estimator != nullptr) {
-			errx(1, "already running");
+			warnx("already running");
+			return 1;
 		}
 
 		estimator::g_estimator = new AttitudePositionEstimatorEKF();
 
 		if (estimator::g_estimator == nullptr) {
-			errx(1, "alloc failed");
+			warnx("alloc failed");
+			return 1;
 		}
 
 		if (OK != estimator::g_estimator->start()) {
 			delete estimator::g_estimator;
 			estimator::g_estimator = nullptr;
-			err(1, "start failed");
+			warnx("start failed");
+			return 1;
 		}
 
 		/* avoid memory fragmentation by not exiting start handler until the task has fully started */
@@ -1558,64 +1562,46 @@ int ekf_att_pos_estimator_main(int argc, char *argv[])
 
 		printf("\n");
 
-		exit(0);
+		return 0;
+	}
+
+	if (estimator::g_estimator == nullptr) {
+		warnx("not running");
+		return 1;
 	}
 
 	if (!strcmp(argv[1], "stop")) {
-		if (estimator::g_estimator == nullptr) {
-			errx(1, "not running");
-		}
 
 		delete estimator::g_estimator;
 		estimator::g_estimator = nullptr;
-		exit(0);
+		return 0;
 	}
 
 	if (!strcmp(argv[1], "status")) {
-		if (estimator::g_estimator) {
-			warnx("running");
+		warnx("running");
 
-			estimator::g_estimator->print_status();
+		estimator::g_estimator->print_status();
 
-			exit(0);
-
-		} else {
-			errx(1, "not running");
-		}
+		return 0;
 	}
 
 	if (!strcmp(argv[1], "trip")) {
-		if (estimator::g_estimator) {
-			int ret = estimator::g_estimator->trip_nan();
+		int ret = estimator::g_estimator->trip_nan();
 
-			exit(ret);
-
-		} else {
-			errx(1, "not running");
-		}
+		return ret;
 	}
 
 	if (!strcmp(argv[1], "logging")) {
-		if (estimator::g_estimator) {
-			int ret = estimator::g_estimator->enable_logging(true);
+		int ret = estimator::g_estimator->enable_logging(true);
 
-			exit(ret);
-
-		} else {
-			errx(1, "not running");
-		}
+		return ret;
 	}
 
 	if (!strcmp(argv[1], "debug")) {
-		if (estimator::g_estimator) {
-			int debug = strtoul(argv[2], NULL, 10);
-			int ret = estimator::g_estimator->set_debuglevel(debug);
+		int debug = strtoul(argv[2], NULL, 10);
+		int ret = estimator::g_estimator->set_debuglevel(debug);
 
-			exit(ret);
-
-		} else {
-			errx(1, "not running");
-		}
+		return ret;
 	}
 
 	warnx("unrecognized command");
diff --git a/src/modules/ekf_att_pos_estimator/estimator_22states.cpp b/src/modules/ekf_att_pos_estimator/estimator_22states.cpp
index 967402fff7..6235aa5b8b 100644
--- a/src/modules/ekf_att_pos_estimator/estimator_22states.cpp
+++ b/src/modules/ekf_att_pos_estimator/estimator_22states.cpp
@@ -2392,9 +2392,9 @@ int AttPosEKF::RecallStates(float* statesForFusion, uint64_t msec)
     if (bestTimeDelta < 200) // only output stored state if < 200 msec retrieval error
     {
         for (size_t i=0; i < EKF_STATE_ESTIMATES; i++) {
-            if (isfinite(storedStates[i][bestStoreIndex])) {
+            if (std::isfinite(storedStates[i][bestStoreIndex])) {
                 statesForFusion[i] = storedStates[i][bestStoreIndex];
-            } else if (isfinite(states[i])) {
+            } else if (std::isfinite(states[i])) {
                 statesForFusion[i] = states[i];
             } else {
                 // There is not much we can do here, except reporting the error we just
@@ -2406,7 +2406,7 @@ int AttPosEKF::RecallStates(float* statesForFusion, uint64_t msec)
     else // otherwise output current state
     {
         for (size_t i = 0; i < EKF_STATE_ESTIMATES; i++) {
-            if (isfinite(states[i])) {
+            if (std::isfinite(states[i])) {
                 statesForFusion[i] = states[i];
             } else {
                 ret++;
@@ -2630,7 +2630,7 @@ float AttPosEKF::ConstrainFloat(float val, float min_val, float max_val)
         ret = val;
     }
 
-    if (!isfinite(val)) {
+    if (!std::isfinite(val)) {
         ekf_debug("constrain: non-finite!");
     }
 
@@ -2922,21 +2922,21 @@ bool AttPosEKF::StatesNaN() {
     bool err = false;
 
     // check all integrators
-    if (!isfinite(summedDelAng.x) || !isfinite(summedDelAng.y) || !isfinite(summedDelAng.z)) {
+    if (!std::isfinite(summedDelAng.x) || !std::isfinite(summedDelAng.y) || !std::isfinite(summedDelAng.z)) {
         current_ekf_state.angNaN = true;
         ekf_debug("summedDelAng NaN: x: %f y: %f z: %f", (double)summedDelAng.x, (double)summedDelAng.y, (double)summedDelAng.z);
         err = true;
         goto out;
     } // delta angles
 
-    if (!isfinite(correctedDelAng.x) || !isfinite(correctedDelAng.y) || !isfinite(correctedDelAng.z)) {
+    if (!std::isfinite(correctedDelAng.x) || !std::isfinite(correctedDelAng.y) || !std::isfinite(correctedDelAng.z)) {
         current_ekf_state.angNaN = true;
         ekf_debug("correctedDelAng NaN: x: %f y: %f z: %f", (double)correctedDelAng.x, (double)correctedDelAng.y, (double)correctedDelAng.z);
         err = true;
         goto out;
     } // delta angles
 
-    if (!isfinite(summedDelVel.x) || !isfinite(summedDelVel.y) || !isfinite(summedDelVel.z)) {
+    if (!std::isfinite(summedDelVel.x) || !std::isfinite(summedDelVel.y) || !std::isfinite(summedDelVel.z)) {
         current_ekf_state.summedDelVelNaN = true;
         ekf_debug("summedDelVel NaN: x: %f y: %f z: %f", (double)summedDelVel.x, (double)summedDelVel.y, (double)summedDelVel.z);
         err = true;
@@ -2946,7 +2946,7 @@ bool AttPosEKF::StatesNaN() {
     // check all states and covariance matrices
     for (size_t i = 0; i < EKF_STATE_ESTIMATES; i++) {
         for (size_t j = 0; j < EKF_STATE_ESTIMATES; j++) {
-            if (!isfinite(KH[i][j])) {
+            if (!std::isfinite(KH[i][j])) {
 
                 current_ekf_state.KHNaN = true;
                 err = true;
@@ -2954,7 +2954,7 @@ bool AttPosEKF::StatesNaN() {
                 goto out;
             } //  intermediate result used for covariance updates
 
-            if (!isfinite(KHP[i][j])) {
+            if (!std::isfinite(KHP[i][j])) {
 
                 current_ekf_state.KHPNaN = true;
                 err = true;
@@ -2962,7 +2962,7 @@ bool AttPosEKF::StatesNaN() {
                 goto out;
             } // intermediate result used for covariance updates
 
-            if (!isfinite(P[i][j])) {
+            if (!std::isfinite(P[i][j])) {
 
                 current_ekf_state.covarianceNaN = true;
                 err = true;
@@ -2970,7 +2970,7 @@ bool AttPosEKF::StatesNaN() {
             } // covariance matrix
         }
 
-        if (!isfinite(Kfusion[i])) {
+        if (!std::isfinite(Kfusion[i])) {
 
             current_ekf_state.kalmanGainsNaN = true;
             ekf_debug("Kfusion NaN");
@@ -2978,7 +2978,7 @@ bool AttPosEKF::StatesNaN() {
             goto out;
         } // Kalman gains
 
-        if (!isfinite(states[i])) {
+        if (!std::isfinite(states[i])) {
 
             current_ekf_state.statesNaN = true;
             ekf_debug("states NaN: i: %u val: %f", i, (double)states[i]);