I think calling functions from gdb could be very useful for embedded developers! Like Julia says, you can start to treat the gdb prompt like a C REPL. Imagine needing to bring up an I2C sensor. Instead of writing some throwaway code to test initial settings and see if the MCU can talk to the sensor (and iterating until you get them right), you could link all of the I2C HAL functions into a “do nothing” program and repeatedly call the HAL functions from the gdb prompt until you find the right settings. Faster than the first example and preferable to using an I2C decoder (like FTDI or Bus Pirate) because you’re using the actual MCU hardware. Like she says, the possibilities seem endless.