Oh yes, my apologies, I got lost in my thoughts. Yes, only RAM, BSS increases but does NOT take up space in flash memory.
The functionality is already there, so I am already at the optimisation step, no more so “premature”.
But I see your point.
Also, be aware of that warning about Vbat in chapter 5.1.2 of the STM32 ref. manual (RM0008).
There is some current leak during the power on/reset sequence of the STM32.
This can be an issue if you still use 3V3 to power Vdd with a 3V non-rechargeable cell and its voltage drop below 2V7.
