Equivalent to IAR’s __no_init variable qualifier

Question

Renesas RX

0

jltrahan 21 Rep. Tue, Jul 9, 2024, 1:50:41 UTC

Hi,

Is there a known workaround/alternative to IAR’s __no_init variable qualifier? The idea is to be able to NOT automatically initialize a variable, not even to 0. The C-runtime start-up code typically copies initialized data by copying from Flash, or in the case of non-initialized data, sets it to 0.

The purpose is to use a bit of RAM to store temporary data after a warm-reset, such as for debugging watchdog resets. I’d like to avoid having to mess with the startup code along with adding a new linker section in RAM.

Open Source Tools Support answered Tue, Jul 9, 2024, 14:45:36 UTC

jltrahan - Tue, Jul 9, 2024, 2:07:17 UTC

I was reading about NOLOAD (linker), but it seems to only apply to Flash/ROM, and not RAM. Is this true?

1 answer

score 1 · Answer 1 · 2024-07-09T14:45:36+00:00

Hello,

Thank you for reaching out to us!

NOLOAD works regardless of the region type.

The behavior of the IAR

__no_init

extension can be replicated by explicitly placing the variable into a special section, and modifying the linker script accordingly:

test.c:
    __attribute__((section(".noinit"))) volatile int flag;

    int main() {
        if(flag == 3)
            return 1;
        flag = 3;
        return 0;
    } 

linkerscript.ld:
  ....
       .noinit (NOLOAD) :
    {
        *(.noinit)
        *(.noinit.*)
    } > RAM
  ....

Please let us know if we can be of further assistance.

__
Best regards,
The Open Source Tools Team