I look at the fix in optiboot and it is simply to pass MCUSR value in parameter to app_start(), so as we are using the stk500boot, we have decided that it was quicker to keep using it.
First step it to compile the stk500boot_v2_mega2560.hex file. I successfully done it but have a footprint difference with the stk500boot_v2_mega2560.hex provided:
/source/ArduinoCore-avr/bootloaders/stk500v2$ make mega2560
-rw-r--r-- 1 sylvain sylvain 16976 Apr 18 11:02 stk500boot_v2_mega2560.hex
-rw-r--r-- 1 sylvain sylvain 21017 Apr 18 11:02 stk500boot_v2_mega2560.hex.old
Even using the source provided by Arduino result in a smaller hex file:
/usr/share/arduino/hardware/arduino/bootloaders/stk500v2$ sudo make mega2560
-rw-r--r-- 1 root root 16743 Apr 18 10:49 stk500boot_v2_mega2560.hex
Is it normal that my hex file is ~5K smaller then the provided one? Am I missing compile flags or Makefile parameters?