llvm dev - May 2017 - Help with setting up ARM embedded clang + lld

On 2 May 2017 at 23:59, Rui Ueyama <ruiu at google.com>
wrote:
> That's interesting. Usually your code wouldn't be gc'ed because
your entire
> code is reachable from _start.
Baremetal doesn't need a _start.

> Does your program depend on the feature that, if no -e option is given, the
> linker sets the beginning of the .text section to the entry point address?
I believe that would help, yes. But there may be linker scripts that
can change that, so you need to be careful.

cheers,
--renato

On Wed, May 3, 2017 at 3:52 AM, Renato Golin <renato.golin at linaro.org>
wrote:
> On 2 May 2017 at 23:59, Rui Ueyama <ruiu at google.com> wrote:
> > That's interesting. Usually your code wouldn't be gc'ed
because your
> entire
> > code is reachable from _start.
>
> Baremetal doesn't need a _start.
>
>
> > Does your program depend on the feature that, if no -e option is
given,
> the
> > linker sets the beginning of the .text section to the entry point
> address?
>
> I believe that would help, yes. But there may be linker scripts that
> can change that, so you need to be careful.
>
If you want to do GC, you still need to teach linkers GC root symbols in
some way, no? Otherwise, linkers cannot determine if a section is live or
not.
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On Wed, May 3, 2017, at 11:51 AM, Rui Ueyama wrote:
> On Wed, May 3, 2017 at 3:52 AM, Renato Golin
> <renato.golin at linaro.org> wrote:>> On 2 May 2017 at 23:59,
Rui Ueyama <ruiu at google.com> wrote:
>>  > That's interesting. Usually your code wouldn't be
gc'ed because
>>  > your entire code is reachable from _start.
>>
>> Baremetal doesn't need a _start.>>
>>
>>  > Does your program depend on the feature that, if no -e option is
>>  > given, the linker sets the beginning of the .text section to the
>>  > entry point address?
>>
>> I believe that would help, yes. But there may be linker scripts
that>>  can change that, so you need to be careful.
> 
> If you want to do GC, you still need to teach linkers GC root symbols
> in some way, no? Otherwise, linkers cannot determine if a section is
> live or not.
Yeah totally. I had marked some sections as used previously but haven't
had a chance to look further into it. I'll try to take some time this
weekend to poke at it further.
The project I'm working on is here:
https://github.com/tannewt/circuitpython/tree/clang/atmel-samd in case
you can't wait.Thanks,
Scott
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