Hello,
On Tue, Jun 10, 2008 at 10:55 PM, Ben Warren <[EMAIL PROTECTED]> wrote:
> Hi,
>
> Not specifically U-boot related, but hopefully a smart person here can help.
>
> I have a weak symbol defined as:
> int cpu_eth_init(bd_t *bis) __attribute((weak, alias("__def_eth_init"))); (1)
>
> I've created a new file in cpu/mpc83xx that includes a real
> implementation of the function:
> int cpu_eth_init(bd_t *bis) (2)
>
> Using objdump, I've verified that this function is making it into
> libmpc8xxx.a, however it doesn't get linked into the final U-boot
> executable. System.map shows cpu_eth_init at the same address as
> __def_eth_init.
>
> If I change (1) to:
> extern int cpu_eth_init(bd_t *bis), (2) gets linked in OK. Of course,
> that's not what I want to do.
>
> I've tried changing the order of the archives that get linked together
> by ld, but nothing seems to work. Since I don't really know what I'm
> doing, I guess that shouldn't be surprising.
>
> Any help would be appreciated.
>
> thanks,
> Ben
>
I've played around a bit more and found that if I move my function to
an existing file containing functions called from elsewhere, my code
gets linked in. Further research shows that a 'feature' of ld is that
it won't pull in a module that only has symbols that have already been
resolved, even if the previously found version is weak.
Mike F, please correct me if I'm wrong but that's what I gather from a
conversion I found you having with the binutils mailing list:
http://sourceware.org/ml/binutils/2008-01/msg00302.html
IMHO, developers should be able to write board and cpu code to
override weak symbols in libraries/drivers without having to worry
about whether the intention was obeyed or not. ld has a switch
'--whole-archive', that will pull in an entire archive, not just the
modules that are referenced elsewhere with strong linkage.
I propose to wrap both the 'board/$(BOARDDIR)/lib$(BOARD).a' and
'cpu/$(CPU)/lib$(CPU).a' arguments to ld in
--whole-module/--no-whole-module in order to accomplish this goal. We
definitely don't want to do this across the board because image size
will increase quite a bit due to unused code. I believe that the
board and cpu code, though, should be mostly free of cruft. If not,
it should be restructured with appropriate CONFIGs, either in
Makefiles or C code.
thoughts?
regards,
Ben
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