diff --git a/sw/airborne/firmwares/rotorcraft/guidance/guidance_v_adapt.c b/sw/airborne/firmwares/rotorcraft/guidance/guidance_v_adapt.c
index 7a5b5f20c3..883ca05ee1 100644
--- a/sw/airborne/firmwares/rotorcraft/guidance/guidance_v_adapt.c
+++ b/sw/airborne/firmwares/rotorcraft/guidance/guidance_v_adapt.c
@@ -171,7 +171,7 @@ void gv_adapt_run(int32_t zdd_meas, int32_t thrust_applied, int32_t zd_ref)
   }
 
   /* Update State */
-  gv_adapt_X = gv_adapt_X + (((int64_t)(K * residual)) >> K_FRAC);
+  gv_adapt_X = gv_adapt_X + ((((int64_t)K * residual)) >> K_FRAC);
 
   /* Output bounds.
    * Don't let it climb over a value that would
diff --git a/sw/airborne/math/pprz_algebra_int.c b/sw/airborne/math/pprz_algebra_int.c
index d1f2373be8..b855c56d8c 100644
--- a/sw/airborne/math/pprz_algebra_int.c
+++ b/sw/airborne/math/pprz_algebra_int.c
@@ -353,12 +353,12 @@ void int32_quat_integrate_fi(struct Int32Quat *q, struct Int64Quat *hr, struct I
 void int32_quat_vmult(struct Int32Vect3 *v_out, struct Int32Quat *q, struct Int32Vect3 *v_in)
 {
   const int64_t _2qi2_m1 = ((q->qi * q->qi) >> (INT32_QUAT_FRAC - 1)) - QUAT1_BFP_OF_REAL(1);
-  const int64_t _2qx2    = (q->qx * q->qx) >> (INT32_QUAT_FRAC - 1);
-  const int64_t _2qy2    = (q->qy * q->qy) >> (INT32_QUAT_FRAC - 1);
-  const int64_t _2qz2    = (q->qz * q->qz) >> (INT32_QUAT_FRAC - 1);
-  const int64_t _2qiqx   = (q->qi * q->qx) >> (INT32_QUAT_FRAC - 1);
-  const int64_t _2qiqy   = (q->qi * q->qy) >> (INT32_QUAT_FRAC - 1);
-  const int64_t _2qiqz   = (q->qi * q->qz) >> (INT32_QUAT_FRAC - 1);
+  const int64_t _2qx2    = ((int64_t const)q->qx * q->qx) >> (INT32_QUAT_FRAC - 1);
+  const int64_t _2qy2    = ((int64_t const)q->qy * q->qy) >> (INT32_QUAT_FRAC - 1);
+  const int64_t _2qz2    = ((int64_t const)q->qz * q->qz) >> (INT32_QUAT_FRAC - 1);
+  const int64_t _2qiqx   = ((int64_t const)q->qi * q->qx) >> (INT32_QUAT_FRAC - 1);
+  const int64_t _2qiqy   = ((int64_t const)q->qi * q->qy) >> (INT32_QUAT_FRAC - 1);
+  const int64_t _2qiqz   = ((int64_t const)q->qi * q->qz) >> (INT32_QUAT_FRAC - 1);
   const int64_t m01 = ((q->qx * q->qy) >> (INT32_QUAT_FRAC - 1)) + _2qiqz;
   const int64_t m02 = ((q->qx * q->qz) >> (INT32_QUAT_FRAC - 1)) - _2qiqy;
   const int64_t m12 = ((q->qy * q->qz) >> (INT32_QUAT_FRAC - 1)) + _2qiqx;
@@ -425,16 +425,18 @@ void int32_quat_of_rmat(struct Int32Quat *q, struct Int32RMat *r)
     const int32_t two_qi_two = TRIG_BFP_OF_REAL(1.) + tr;
     uint32_t two_qi = int32_sqrt(two_qi_two << INT32_TRIG_FRAC);
     two_qi = two_qi << (INT32_QUAT_FRAC - INT32_TRIG_FRAC);
-    q->qi = two_qi / 2;
-    q->qx = ((RMAT_ELMT(*r, 1, 2) - RMAT_ELMT(*r, 2, 1)) <<
-             (INT32_QUAT_FRAC - INT32_TRIG_FRAC + INT32_QUAT_FRAC - 1))
-            / two_qi;
-    q->qy = ((RMAT_ELMT(*r, 2, 0) - RMAT_ELMT(*r, 0, 2)) <<
-             (INT32_QUAT_FRAC - INT32_TRIG_FRAC + INT32_QUAT_FRAC - 1))
-            / two_qi;
-    q->qz = ((RMAT_ELMT(*r, 0, 1) - RMAT_ELMT(*r, 1, 0)) <<
-             (INT32_QUAT_FRAC - INT32_TRIG_FRAC + INT32_QUAT_FRAC - 1))
-            / two_qi;
+    if (two_qi != 0) {
+      q->qi = two_qi / 2;
+      q->qx = ((RMAT_ELMT(*r, 1, 2) - RMAT_ELMT(*r, 2, 1)) <<
+               (INT32_QUAT_FRAC - INT32_TRIG_FRAC + INT32_QUAT_FRAC - 1))
+              / two_qi;
+      q->qy = ((RMAT_ELMT(*r, 2, 0) - RMAT_ELMT(*r, 0, 2)) <<
+               (INT32_QUAT_FRAC - INT32_TRIG_FRAC + INT32_QUAT_FRAC - 1))
+              / two_qi;
+      q->qz = ((RMAT_ELMT(*r, 0, 1) - RMAT_ELMT(*r, 1, 0)) <<
+               (INT32_QUAT_FRAC - INT32_TRIG_FRAC + INT32_QUAT_FRAC - 1))
+              / two_qi;
+    }
   } else {
     if (RMAT_ELMT(*r, 0, 0) > RMAT_ELMT(*r, 1, 1) &&
         RMAT_ELMT(*r, 0, 0) > RMAT_ELMT(*r, 2, 2)) {
@@ -442,46 +444,52 @@ void int32_quat_of_rmat(struct Int32Quat *q, struct Int32RMat *r)
                                  - RMAT_ELMT(*r, 2, 2) + TRIG_BFP_OF_REAL(1.);
       uint32_t two_qx = int32_sqrt(two_qx_two << INT32_TRIG_FRAC);
       two_qx = two_qx << (INT32_QUAT_FRAC - INT32_TRIG_FRAC);
-      q->qi = ((RMAT_ELMT(*r, 1, 2) - RMAT_ELMT(*r, 2, 1)) <<
-               (INT32_QUAT_FRAC - INT32_TRIG_FRAC + INT32_QUAT_FRAC - 1))
-              / two_qx;
-      q->qx = two_qx / 2;
-      q->qy = ((RMAT_ELMT(*r, 0, 1) + RMAT_ELMT(*r, 1, 0)) <<
-               (INT32_QUAT_FRAC - INT32_TRIG_FRAC + INT32_QUAT_FRAC - 1))
-              / two_qx;
-      q->qz = ((RMAT_ELMT(*r, 2, 0) + RMAT_ELMT(*r, 0, 2)) <<
-               (INT32_QUAT_FRAC - INT32_TRIG_FRAC + INT32_QUAT_FRAC - 1))
-              / two_qx;
+      if (two_qx != 0) {
+        q->qi = ((RMAT_ELMT(*r, 1, 2) - RMAT_ELMT(*r, 2, 1)) <<
+                 (INT32_QUAT_FRAC - INT32_TRIG_FRAC + INT32_QUAT_FRAC - 1))
+                / two_qx;
+        q->qx = two_qx / 2;
+        q->qy = ((RMAT_ELMT(*r, 0, 1) + RMAT_ELMT(*r, 1, 0)) <<
+                 (INT32_QUAT_FRAC - INT32_TRIG_FRAC + INT32_QUAT_FRAC - 1))
+                / two_qx;
+        q->qz = ((RMAT_ELMT(*r, 2, 0) + RMAT_ELMT(*r, 0, 2)) <<
+                 (INT32_QUAT_FRAC - INT32_TRIG_FRAC + INT32_QUAT_FRAC - 1))
+                / two_qx;
+      }
     } else if (RMAT_ELMT(*r, 1, 1) > RMAT_ELMT(*r, 2, 2)) {
       const int32_t two_qy_two = RMAT_ELMT(*r, 1, 1) - RMAT_ELMT(*r, 0, 0)
                                  - RMAT_ELMT(*r, 2, 2) + TRIG_BFP_OF_REAL(1.);
       uint32_t two_qy = int32_sqrt(two_qy_two << INT32_TRIG_FRAC);
       two_qy = two_qy << (INT32_QUAT_FRAC - INT32_TRIG_FRAC);
-      q->qi = ((RMAT_ELMT(*r, 2, 0) - RMAT_ELMT(*r, 0, 2)) <<
-               (INT32_QUAT_FRAC - INT32_TRIG_FRAC + INT32_QUAT_FRAC - 1))
-              / two_qy;
-      q->qx = ((RMAT_ELMT(*r, 0, 1) + RMAT_ELMT(*r, 1, 0)) <<
-               (INT32_QUAT_FRAC - INT32_TRIG_FRAC + INT32_QUAT_FRAC - 1))
-              / two_qy;
-      q->qy = two_qy / 2;
-      q->qz = ((RMAT_ELMT(*r, 1, 2) + RMAT_ELMT(*r, 2, 1)) <<
-               (INT32_QUAT_FRAC - INT32_TRIG_FRAC + INT32_QUAT_FRAC - 1))
-              / two_qy;
+      if (two_qy != 0) {
+        q->qi = ((RMAT_ELMT(*r, 2, 0) - RMAT_ELMT(*r, 0, 2)) <<
+                 (INT32_QUAT_FRAC - INT32_TRIG_FRAC + INT32_QUAT_FRAC - 1))
+                / two_qy;
+        q->qx = ((RMAT_ELMT(*r, 0, 1) + RMAT_ELMT(*r, 1, 0)) <<
+                 (INT32_QUAT_FRAC - INT32_TRIG_FRAC + INT32_QUAT_FRAC - 1))
+                / two_qy;
+        q->qy = two_qy / 2;
+        q->qz = ((RMAT_ELMT(*r, 1, 2) + RMAT_ELMT(*r, 2, 1)) <<
+                 (INT32_QUAT_FRAC - INT32_TRIG_FRAC + INT32_QUAT_FRAC - 1))
+                / two_qy;
+      }
     } else {
       const int32_t two_qz_two = RMAT_ELMT(*r, 2, 2) - RMAT_ELMT(*r, 0, 0)
                                  - RMAT_ELMT(*r, 1, 1) + TRIG_BFP_OF_REAL(1.);
       uint32_t two_qz = int32_sqrt(two_qz_two << INT32_TRIG_FRAC);
       two_qz = two_qz << (INT32_QUAT_FRAC - INT32_TRIG_FRAC);
-      q->qi = ((RMAT_ELMT(*r, 0, 1) - RMAT_ELMT(*r, 1, 0)) <<
-               (INT32_QUAT_FRAC - INT32_TRIG_FRAC + INT32_QUAT_FRAC - 1))
-              / two_qz;
-      q->qx = ((RMAT_ELMT(*r, 2, 0) + RMAT_ELMT(*r, 0, 2)) <<
-               (INT32_QUAT_FRAC - INT32_TRIG_FRAC + INT32_QUAT_FRAC - 1))
-              / two_qz;
-      q->qy = ((RMAT_ELMT(*r, 1, 2) + RMAT_ELMT(*r, 2, 1)) <<
-               (INT32_QUAT_FRAC - INT32_TRIG_FRAC + INT32_QUAT_FRAC - 1))
-              / two_qz;
-      q->qz = two_qz / 2;
+      if (two_qz != 0) {
+        q->qi = ((RMAT_ELMT(*r, 0, 1) - RMAT_ELMT(*r, 1, 0)) <<
+                 (INT32_QUAT_FRAC - INT32_TRIG_FRAC + INT32_QUAT_FRAC - 1))
+                / two_qz;
+        q->qx = ((RMAT_ELMT(*r, 2, 0) + RMAT_ELMT(*r, 0, 2)) <<
+                 (INT32_QUAT_FRAC - INT32_TRIG_FRAC + INT32_QUAT_FRAC - 1))
+                / two_qz;
+        q->qy = ((RMAT_ELMT(*r, 1, 2) + RMAT_ELMT(*r, 2, 1)) <<
+                 (INT32_QUAT_FRAC - INT32_TRIG_FRAC + INT32_QUAT_FRAC - 1))
+                / two_qz;
+        q->qz = two_qz / 2;
+      }
     }
   }
 }
diff --git a/sw/simulator/nps/nps_flightgear.c b/sw/simulator/nps/nps_flightgear.c
index 42dcf7f89b..d7331b5ec4 100644
--- a/sw/simulator/nps/nps_flightgear.c
+++ b/sw/simulator/nps/nps_flightgear.c
@@ -61,8 +61,15 @@ void nps_flightgear_init(const char *host,  unsigned int port, unsigned int port
   if (port_in > 0) {
     struct sockaddr_in addr_in;
     flightgear.socket_in = socket(PF_INET, SOCK_DGRAM, pte->p_proto);
-    setsockopt(flightgear.socket_in, SOL_SOCKET, SO_REUSEADDR,
-        &so_reuseaddr, sizeof(so_reuseaddr));
+    if (flightgear.socket_in < 0) {
+      perror("nps_flightgear_init socket()");
+      exit(errno);
+    }
+    if ( setsockopt(flightgear.socket_in, SOL_SOCKET, SO_REUSEADDR,
+        &so_reuseaddr, sizeof(so_reuseaddr)) == -1) {
+      perror("nps_flightgear_init setsockopt()");
+      exit(errno);
+    }
     addr_in.sin_family = PF_INET;
     addr_in.sin_port = htons(port_in);
     addr_in.sin_addr.s_addr = htonl(INADDR_ANY);
diff --git a/sw/simulator/nps/nps_main.c b/sw/simulator/nps/nps_main.c
index 01b15a5741..e716bc14df 100644
--- a/sw/simulator/nps/nps_main.c
+++ b/sw/simulator/nps/nps_main.c
@@ -369,7 +369,7 @@ static bool nps_main_parse_options(int argc, char **argv)
             nps_main.host_time_factor = atof(optarg); break;
           case 8:
             nps_main.fg_fdm = 1; break;
-	  case 9:
+          case 9:
             nps_main.fg_port_in = atoi(optarg); break;
         }
         break;
@@ -383,7 +383,7 @@ static bool nps_main_parse_options(int argc, char **argv)
         fprintf(stderr, usage, argv[0]);
         exit(0);
 
-      default: /* ’?’ */
+      default:
         printf("?? getopt returned character code 0%o ??\n", c);
         fprintf(stderr, usage, argv[0]);
         exit(EXIT_FAILURE);
diff --git a/sw/simulator/nps/nps_radio_control_spektrum.c b/sw/simulator/nps/nps_radio_control_spektrum.c
index d065a8a1fe..a84db7319b 100644
--- a/sw/simulator/nps/nps_radio_control_spektrum.c
+++ b/sw/simulator/nps/nps_radio_control_spektrum.c
@@ -38,9 +38,13 @@ int nps_radio_control_spektrum_init(const char *device)
   termios.c_iflag &= ~(IGNBRK | BRKINT | PARMRK | INPCK | ISTRIP | INLCR | IGNCR
                        | ICRNL | IUCLC | IXON | IXANY | IXOFF | IMAXBEL);
   termios.c_iflag |= IGNPAR;
+
+  termios.c_cflag = 0; // properly initialize variable
   /* control modes*/
   termios.c_cflag &= ~(CSIZE | PARENB | CRTSCTS | PARODD | HUPCL);
   termios.c_cflag |= CREAD | CS8 | CSTOPB | CLOCAL;
+
+  termios.c_lflag = 0; // properly initialize variable
   /* local modes  */
   termios.c_lflag &= ~(ISIG | ICANON | IEXTEN | ECHO | FLUSHO | PENDIN);
   termios.c_lflag |= NOFLSH;