I wanted to report a bug I have found in the nRF52 SDK (17.0.2, 16.0, and 15.3, possibly more) in nrf_ble_ancs_c.h that causes compiler issues. For SDK 17.0.2, at line 146, it says
"sstatic ble_ancs_c_t _name[_cnt];" instead of "static ble_ancs_c_t _name[_cnt];". This is specifically in the define BLE_ANCS_C_ARRAY_DEF, so only people who use this array version would have the issue, though admittedly it's an easy fix.