arm-none-eabi-size prints larger bss size than it is according to *.map file

[Jakub J.]

Hello

I came across interesting problem I couldn't find answer to.

In my project bss size printed by arm-none-eabi-size is larger than the value that can be calculated basing on *.map file. Using arm-gcc 4.9 2015q3 + NRF SDK10 , compiling code for nrf51822,

Short example:

arm-none-eabi-size bootloader.out

  text      data   bss    dec      hex      filename

  38476     276    4734   43486    a9de     bootloader.out

Part of *.map file:

        0x20002d10                . = ALIGN (0x4)
        0x20002d10                __bss_start__ = .
        (...)
        0x20003b50                . = ALIGN (0x4)
        0x20003b50                __bss_end__ = .

Clearly size of (bss_end - bss_start = 3648) is different from the one printed above. What causes that difference?

Bss part of linker script file:

.bss :
{
	. = ALIGN(4);
	__bss_start__ = .;
	*(.bss*)
	*(COMMON)
	. = ALIGN(4);
	__bss_end__ = .;
} > RAM

[bjorn-spockeli]

Do you see this issue when you compile one of the example applications in the SDK, e.g. ble_app_hrs?

[Jakub J.]

For \SDK10\examples\ble_peripheral\ble_app_hrs\pca10028\s110\armgcc is fine. However the issue apppears for example for \SDK10\examples\dfu\bootloader\pca10028\single_bank_serial_s110\armgcc.

[bjorn-spockeli]

I suspect that it is the bootloader settings flash page, which is set to NOLOAD in the linker script.

[Jakub J.]

Takk! that's it

[bjorn-spockeli]

Happy to help :)