Re: [avr-gcc-list] Variable __data_end variable not passed through to linker for use in __heap_start?

[Ned Konz]

On Apr 9, 2006, at 8:41 PM, <address@hidden>  
<address@hidden> wrote:

> Hi all:
>
> I am running winavr 2006*, on an atmega128 with 32k of XRAM mapped to
> 0x8000->0xFFFF. I would like the .bss memory section to be  
> allocated by
> the linker in the internal RAM, while I'd like the .data section  
> and the
> __malloc_heap_start to both be in XRAM. .bss being in IRAM is not  
> really
> negotiable, and I'd much prefer .data to live in XRAM, due to the  
> larger
> size of that section.
>
> Unfortunately, the makefile I'm using doesn't seem to want to allocate
> the __malloc_heap_start variable to the __data_end.
>
> I've tried adding the following options, with no success:
>
>     LDFLAGS += -Wl,--section-start,.bss=0x800100 \
>               -Wl,--section-start,.data=0x808000) \
>               -Wl,--defsym,__heap_start=__data_end \
>               -Wl,--defsym,__heap_end=0x80FFFF \
>
> The problem I have is that any memory I allocate with malloc ends  
> up in
> the internal RAM, straight after .bss.
>
> However, if I hard-code the __heap_start variable (to, say,  
> 0x809000), I
> have no problems - the malloc'ed memory is allocated in XRAM. This  
> is a
> less than ideal situation, obviously, however I don't seem to be  
> able to
> pass through the __data_end variable into the __heap_start (and  
> onwards
> to __malloc_heap_start).
>
> Anyone run into this before, and/or any suggestions??

Sure: why not just define a custom linker script?

It's quicker than all that command-line stuff anyway.

Anyhow, seems like someone was complaining that the command-line args  
didn't work anyhow.

Try the attached.

It results in:

.data           0x00808000        0x6
                0x00808000                PROVIDE (__data_start, .)
                0x00808002                __malloc_heap_start
                0x00808000                __malloc_heap_end
                0x00808004                __malloc_margin
                0x00808006                _edata = .
                0x00808006                PROVIDE (__data_end, .)
                0x00808006                PROVIDE (__heap_start, .)

.bss            0x00800060        0x4
                0x00800060                PROVIDE (__bss_start, .)
                0x0080ffff                __heap_end = 0x80ffff



--
Ned Konz
address@hidden

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