ESP32 save/retrieve core dump

Hello, I have several ESP's in remote locations, and I was quite happy with EspSaveCrash library to investigate some intermittent crashes. Transitioning to ESP 32 I discovered that EspSaveCrash no longer works, due to (I guess) ESP232 doesn't call the custom_crash_callback. That is very disappointing! Anyway, I found in the standard ESP32 library esp_core_dump.h with some functions that look interesting, like esp_core_dump_to_flash(); and esp_core_dump_to_uart();. I can successfully compile but the linker says: undefined reference to esp_core_dump_to_uart() Any idea? Any suggestions to save crash information "somewhere" and retrieve them after a reboot?