Startup & data initialisation problems with gcc4.9.3 under eclipse environnement

[thln]

Hi,

I'm working on nRF52822 device with gcc4.9.3 compiler under eclipse environnement (with gnuarm toolchain plugin).

I have some problems with data initialisation. To check what is wrong I made this simple example:

volatile uint32_t test_data=0x12345678;
volatile uint32_t test_bss = 0;

int main(void) {
	printf("test data %08X\n", (int)test_data);
	test_data = 0;

	printf("test bss %d\n", (int)test_bss);
	test_bss = 1;
}

On the first launch, the console shows:

test data 12345678
test bss 980  

Then I generate a reset to restart my test, the console shows:

test data 00000000
test bss 1

So

a) the "test_data" value is well initialized on the first time, but not on the following ones.

b) the "test_bss" value is never initialized.

Note, my linker options are -T "D:\Eclipse\eclipse64-mars\workbench.arm\nRF52\nRF52_AA.ld" -Xlinker --gc-sections -Wl,-Map,"nRF52.map" --specs=rdimon.specs

I use rdimon library to have the SWO console.

If I try to debug the code, in the statup routine form "gcc_startup_nrf52.s" file, some values (addresses) are not correct.

Reset_Handler:
    ldr r1, =__etext					; <= value correspond to the end of text section
    ldr r2, =__data_start__				; <= value correspond to the start of the RAM (0x20000000)
    ldr r3, =__bss_start__				; !! value = 0x8000 doesn't correspond to the start of bss section !!
...

So the initialization of data is not done here. I guess that it's done inside crt0 routine.

Then to initialize the bss section I've compiled with -D__STARTUP_CLEAR_BSS to be sure the the following code will be added.

#ifdef __STARTUP_CLEAR_BSS
    ldr r1, =__bss_start__				; !! value still set to 0x8000
    ldr r2, =__bss_end__				; !! value = 0x8000 doesn't correspond to the end of bss section !!

    movs r0, 0

    subs r2, r1
    ble .L_loop3_done

.L_loop3:
    subs r2, #4
    str r0, [r1, r2]
    bgt .L_loop3
    
.L_loop3_done:
#endif /* __STARTUP_CLEAR_BSS */	

My linker script is like this

MEMORY
{
  FLASH (rx) : ORIGIN = 0x00000000, LENGTH = 0x80000
  RAM (rwx) :  ORIGIN = 0x20000000, LENGTH = 0x10000
}
...
    .bss :
    {
        . = ALIGN(4);
        __bss_start__ = .;
        *(.bss*)				# bss section content should be located between __bss_start__ and __bss_end__
        *(COMMON)
        . = ALIGN(4);
        __bss_end__ = .;
    } > RAM
...

1. I don't know why bss_start and bss_end are not set to right values

2. I don't know why crt routine doesn't initialize correctly the memory

Thanks for reply.

Regards, Thierry

[RK]

I don't understand how that is happening. Can you try compiling without the rdimon specs file to see if that makes a difference, if it does, we should look at what's in the specs file.