diff --git a/apps/examples/pwm/pwm_main.c b/apps/examples/pwm/pwm_main.c
index 775bdba6b1..a46c10f55c 100644
--- a/apps/examples/pwm/pwm_main.c
+++ b/apps/examples/pwm/pwm_main.c
@@ -48,6 +48,7 @@
 #include <fcntl.h>
 #include <errno.h>
 #include <debug.h>
+#include <string.h>
 
 #include <nuttx/pwm.h>
 
diff --git a/nuttx/drivers/mmcsd/mmcsd_spi.c b/nuttx/drivers/mmcsd/mmcsd_spi.c
index 7dbadc55fe..39b5705812 100644
--- a/nuttx/drivers/mmcsd/mmcsd_spi.c
+++ b/nuttx/drivers/mmcsd/mmcsd_spi.c
@@ -508,7 +508,7 @@ static uint32_t mmcsd_sendcmd(FAR struct mmcsd_slot_s *slot,
       }
       break;
 
-    /* The R3 response is 5 bytes long */
+    /* The R3 response is 5 bytes long. The first byte is identical to R1. */
 
     case MMCSD_CMDRESP_R3:
       {
@@ -520,8 +520,10 @@ static uint32_t mmcsd_sendcmd(FAR struct mmcsd_slot_s *slot,
         fvdbg("CMD%d[%08x] R1=%02x OCR=%08x\n",
               cmd->cmd & 0x3f, arg, response, slot->ocr);
       }
+      break;
+
+    /* The R7 response is 5 bytes long. The first byte is identical to R1. */
 
-    /* The R7 response is 5 bytes long */
     case MMCSD_CMDRESP_R7:
     default:
       {
diff --git a/nuttx/sched/mq_open.c b/nuttx/sched/mq_open.c
index 5e1b9b1377..89d80f072a 100644
--- a/nuttx/sched/mq_open.c
+++ b/nuttx/sched/mq_open.c
@@ -113,7 +113,6 @@ mqd_t mq_open(const char *mq_name, int oflags, ...)
   FAR msgq_t     *msgq;
   mqd_t           mqdes = NULL;
   va_list         arg;          /* Points to each un-named argument */
-  mode_t          mode;         /* MQ creation mode parameter (ignored) */
   struct mq_attr *attr;         /* MQ creation attributes */
   int             namelen;      /* Length of MQ name */
 
@@ -170,7 +169,7 @@ mqd_t mq_open(const char *mq_name, int oflags, ...)
                        */
 
                       va_start(arg, oflags);
-                      mode = va_arg(arg, mode_t);
+                      (void)va_arg(arg, mode_t); /* MQ creation mode parameter (ignored) */
                       attr = va_arg(arg, struct mq_attr*);
 
                       /* Initialize the new named message queue */
diff --git a/nuttx/sched/sem_open.c b/nuttx/sched/sem_open.c
index 817c36b49b..b2b76fe380 100644
--- a/nuttx/sched/sem_open.c
+++ b/nuttx/sched/sem_open.c
@@ -120,7 +120,6 @@ FAR sem_t *sem_open (FAR const char *name, int oflag, ...)
   FAR nsem_t  *psem;
   FAR sem_t   *sem = (FAR sem_t*)ERROR;
   va_list      arg;          /* Points to each un-named argument */
-  mode_t       mode;         /* Creation mode parameter (ignored) */
   unsigned int value;        /* Semaphore value parameter */
 
   /* Make sure that a non-NULL name is supplied */
@@ -165,7 +164,7 @@ FAR sem_t *sem_open (FAR const char *name, int oflag, ...)
                */
 
               va_start(arg, oflag);
-              mode = va_arg(arg, mode_t);
+              (void)va_arg(arg, mode_t); /* Creation mode parameter (ignored) */
               value = va_arg(arg, unsigned int);
 
               /* Verify that a legal initial value was selected. */