Remove unreachable code

IAR generates warning Pe111 'statement is unreachable'. In a couple of
cases, replace return statements with TU_ATTR_FALLTHROUGH; because some
compilers apparently can't figure out that the return statements are
unreachable but do whinge about an imagined fall-through without them!

examples/device/audio_4_channel_mic/src/main.c

@@ -99,9 +99,6 @@ int main(void)
     led_blinking_task();
     audio_task();
   }
-
-
-  return 0;
 }
 
 //--------------------------------------------------------------------+

examples/device/audio_test/src/main.c

@@ -100,9 +100,6 @@ int main(void)
     led_blinking_task();
     audio_task();
   }
-
-
-  return 0;
 }
 
 //--------------------------------------------------------------------+

examples/device/board_test/src/main.c

@@ -67,8 +67,6 @@ int main(void)
       led_state = 1 - led_state; // toggle
     }
   }
-
-  return 0;
 }
 
 #if CFG_TUSB_MCU == OPT_MCU_ESP32S2 || CFG_TUSB_MCU == OPT_MCU_ESP32S3

examples/device/cdc_dual_ports/src/main.c

@@ -47,8 +47,6 @@ int main(void)
     tud_task(); // tinyusb device task
     cdc_task();
   }
-
-  return 0;
 }
 
 // echo to either Serial0 or Serial1

examples/device/cdc_msc/src/main.c

@@ -65,8 +65,6 @@ int main(void)
 
     cdc_task();
   }
-
-  return 0;
 }
 
 //--------------------------------------------------------------------+

examples/device/dfu/src/main.c

@@ -82,8 +82,6 @@ int main(void)
     tud_task(); // tinyusb device task
     led_blinking_task();
   }
-
-  return 0;
 }
 
 //--------------------------------------------------------------------+

examples/device/dfu_runtime/src/main.c

@@ -77,8 +77,6 @@ int main(void)
     tud_task(); // tinyusb device task
     led_blinking_task();
   }
-
-  return 0;
 }
 
 //--------------------------------------------------------------------+

examples/device/dynamic_configuration/src/main.c

@@ -66,8 +66,6 @@ int main(void)
     cdc_task();
     midi_task();
   }
-
-  return 0;
 }
 
 //--------------------------------------------------------------------+

examples/device/hid_composite/src/main.c

@@ -67,8 +67,6 @@ int main(void)
 
     hid_task();
   }
-
-  return 0;
 }
 
 //--------------------------------------------------------------------+

examples/device/hid_generic_inout/src/main.c

@@ -88,8 +88,6 @@ int main(void)
     tud_task(); // tinyusb device task
     led_blinking_task();
   }
-
-  return 0;
 }
 
 //--------------------------------------------------------------------+

examples/device/hid_multiple_interface/src/main.c

@@ -71,8 +71,6 @@ int main(void)
 
     hid_task();
   }
-
-  return 0;
 }
 
 //--------------------------------------------------------------------+

examples/device/midi_test/src/main.c

@@ -71,9 +71,6 @@ int main(void)
     led_blinking_task();
     midi_task();
   }
-
-
-  return 0;
 }
 
 //--------------------------------------------------------------------+

examples/device/msc_dual_lun/src/main.c

@@ -62,8 +62,6 @@ int main(void)
     tud_task(); // tinyusb device task
     led_blinking_task();
   }
-
-  return 0;
 }
 
 //--------------------------------------------------------------------+

examples/device/uac2_headset/src/main.c

@@ -113,8 +113,6 @@ int main(void)
     audio_task();
     led_blinking_task();
   }
-
-  return 0;
 }
 
 //--------------------------------------------------------------------+

examples/device/usbtmc/src/main.c

@@ -63,8 +63,6 @@ int main(void)
     led_blinking_task();
     usbtmc_app_task_iter();
   }
-
-  return 0;
 }
 
 //--------------------------------------------------------------------+

examples/device/usbtmc/src/usbtmc_app.c

@@ -254,7 +254,6 @@ void usbtmc_app_task_iter(void) {
     break;
   default:
     TU_ASSERT(false,);
-    return;
   }
 }
 

examples/device/video_capture/src/main.c

@@ -66,8 +66,6 @@ int main(void)
 
     video_task();
   }
-
-  return 0;
 }
 
 //--------------------------------------------------------------------+

examples/device/webusb_serial/src/main.c

@@ -103,8 +103,6 @@ int main(void)
     webserial_task();
     led_blinking_task();
   }
-
-  return 0;
 }
 
 // send characters to both CDC and WebUSB

examples/host/cdc_msc_hid/src/main.c

@@ -62,8 +62,6 @@ int main(void)
     hid_app_task();
 #endif
   }
-
-  return 0;
 }
 
 //--------------------------------------------------------------------+

examples/host/hid_controller/src/main.c

@@ -68,8 +68,6 @@ int main(void)
     hid_app_task();
 #endif
   }
-
-  return 0;
 }
 
 //--------------------------------------------------------------------+

src/class/usbtmc/usbtmc_device.c

@@ -496,7 +496,6 @@ bool usbtmcd_xfer_cb(uint8_t rhport, uint8_t ep_addr, xfer_result_t result, uint
       default:
         usbd_edpt_stall(rhport, usbtmc_state.ep_bulk_out);
         TU_VERIFY(false);
-        return false;
       }
       return true;
 
@@ -509,8 +508,8 @@ bool usbtmcd_xfer_cb(uint8_t rhport, uint8_t ep_addr, xfer_result_t result, uint
       return true;
 
     case STATE_ABORTING_BULK_OUT:
-      TU_VERIFY(false);
-      return false; // Should be stalled by now, shouldn't have received a packet.
+      TU_VERIFY(false); // Should be stalled by now, shouldn't have received a packet.
+      TU_ATTR_FALLTHROUGH; // Not really - some compilers can't figure out that the above macro always returns.
 
     case STATE_TX_REQUESTED:
     case STATE_TX_INITIATED:
@@ -567,7 +566,6 @@ bool usbtmcd_xfer_cb(uint8_t rhport, uint8_t ep_addr, xfer_result_t result, uint
 
     default:
       TU_ASSERT(false);
-      return false;
     }
   }
   else if (ep_addr == usbtmc_state.ep_int_in) {
@@ -872,15 +870,13 @@ bool usbtmcd_control_xfer_cb(uint8_t rhport, uint8_t stage, tusb_control_request
     {
       TU_VERIFY(request->bmRequestType == 0xA1); // in,class,interface
       TU_VERIFY(false);
-      return false;
+      TU_ATTR_FALLTHROUGH; // Not really - some compilers can't figure out that the above macro always returns.
     }
 #endif
 
   default:
     TU_VERIFY(false);
-    return false;
   }
-  TU_VERIFY(false);
 }
 
 #endif /* CFG_TUD_TSMC */

src/class/video/video_device.c

@@ -943,7 +943,6 @@ static int handle_video_stm_req(uint8_t rhport, uint8_t stage,
 
     default: return VIDEO_ERROR_INVALID_REQUEST;
   }
-  return VIDEO_ERROR_UNKNOWN;
 }
 
 //--------------------------------------------------------------------+

src/portable/raspberrypi/rp2040/hcd_rp2040.c

@@ -432,8 +432,7 @@ tusb_speed_t hcd_port_speed_get(uint8_t rhport)
       case 2:
           return TUSB_SPEED_FULL;
       default:
-          panic("Invalid speed\n");
-          return TUSB_SPEED_INVALID;
+          panic("Invalid speed\n"); // does not return
   }
 }
 
@@ -599,8 +598,7 @@ bool hcd_edpt_clear_stall(uint8_t dev_addr, uint8_t ep_addr)
     (void) dev_addr;
     (void) ep_addr;
 
-    panic("hcd_clear_stall");
-    return true;
+    panic("hcd_clear_stall"); // does not return
 }
 
 #endif