HIDS Mouse application - err_code set but not used

Question

Hi! I am trying to control volume up/down, and for the future possibly a few other functions within the ID 3 tag of the HID descriptor. 
 I am using the ble hids mouse example from SDK 13.0.0 for nRF52832, but I'm facing an error which makes me unable to compile the project. I'm using Eclipse 4.6.3. 
 I've taken the mouse_movement_send function as example, as well as an example written for nRF51, and written my own function to send volume control commands.
The error says "variable 'err_code' set but not used", as depicted below. Probably the ble_hids_inp_rep_send function does not operate properly, I'm just not able to see what's wrong right now. 
 Hope anyone is able to give a guiding hint =) 
 Description	Resource	Path	Location	Type
variable 'err_code' set but not used [-Werror=unused-but-set-variable]	main.c	/ph_ble_hids_mouse/Application	line 1223	C/C++ Problem 
 /**@brief Function for sending volume control actions
*
*
*/ 
 static void volume_control_send(int8_t vol_ch_up, int8_t vol_ch_down, int8_t vol_ch_pause)
{
ret_code_t err_code; 
 uint8_t buffer[INPUT_REP_MEDIA_PLAYER_LEN];
// uint8_t buffer;

 APP_ERROR_CHECK_BOOL(INPUT_REP_MEDIA_PLAYER_LEN == 1);

 if(vol_ch_up == 0xE9)
 {
 buffer[0] = 0xE9;
 }
 if(vol_ch_down == 0xEA)
 {
 buffer[0] = 0xEA;
 }
 if(vol_ch_pause == 0xCD)
 {
 buffer[0] = 0xCD;
 }
 err_code = ble_hids_inp_rep_send (&m_hids,
 INPUT_REP_REF_MPLAYER_ID,
 INPUT_REP_MEDIA_PLAYER_LEN,
 (uint8_t*)buffer);

 vol_ch_up=0, vol_ch_down=0, vol_ch_pause=0, buffer[0]=0;
 
 } 
 case BSP_EVENT_KEY_0:
 if (m_conn_handle != BLE_CONN_HANDLE_INVALID)
 {
 //mouse_movement_send(-MOVEMENT_SPEED, 0);
 volume_control_send(0xE9, 0, 0);
 }
 break;

 case BSP_EVENT_KEY_1:
 if (m_conn_handle != BLE_CONN_HANDLE_INVALID)
 {
 //mouse_movement_send(0, -MOVEMENT_SPEED);
 volume_control_send(0, 0, 0xCD);
 }
 break;

 case BSP_EVENT_KEY_2:
 if (m_conn_handle != BLE_CONN_HANDLE_INVALID)
 {
 //mouse_movement_send(MOVEMENT_SPEED, 0);
 volume_control_send(0, 0xEA, 0);
 }
 break;

 case BSP_EVENT_KEY_3:
 if (m_conn_handle != BLE_CONN_HANDLE_INVALID)
 {
 mouse_movement_send(0, MOVEMENT_SPEED);
 }
 break;

 default:
 break;

Hung Bui · Accepted Answer

I think it's pretty clear what the error say: 
 variable 'err_code' set but not used
 
 You set the err_code but you never use the value of it, that's why the warning is thrown. Most likely you configure gcc to treat warnings as errors 
 But what you should do is to check the value of the err_code and throw an assert if it's not NRF_SUCCESS.

HIDS Mouse application - err_code set but not used

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