[Buildroot] Passing arguments to the linker when external toolchain is used.

[Ronny Meeus]

On Sun, Nov 25, 2012 at 9:44 PM, Arnout Vandecappelle <arnout at mind.be> wrote:
> On 25/11/12 18:23, Ronny Meeus wrote:
>>>>
>>>> >>  In my application we need to create partially linked objects that
>>>> >> will
>>>> >>  be linked together in a final link step.
>>>> >>  I see that the correct options (ABI etc) are passed to the compiler
>>>> >>  via the ext-toolchain-wrapper construction, but for the linker this
>>>> >>  technique is not used. It is directly invoked without modifying the
>>>> >>  command line. If I want to create this partially linked file, I need
>>>> >>  to pass an extra option the linker to indicate that is needs to use
>>>> >>  the N32 abi (-melf32btsmipn32).
>>>
>>> >
>>> >
>>> >    First of all, I don't understand why ld needs any option that we
>>> > normally
>>> >  pass to the compiler.  Do the -march, -mtune and -mfpu options even
>>> > work
>>> >  in ld?
>>
>> I think you miss-understood my mail.
>> The linker needs a different option (-melf32btsmipn32) while the
>> compiler needs -march, -mtune and -mfpu etc.
>> For the compiler there is no issue, it is the linker for which no
>> options are passed.
>
>
>  In that case, why not just pass them with LDFLAGS?
>

Our SW is build in 2 parts: the Linux kernel, buildroot and other
components are build via buildroot itself.
Next to this we also have other applications that we build in with "a
private build infrastructure" using the toolchain, include files etc
of buildroot.

By adding the extra linker parameters with the wrapper construction we
can transparantly introduce a new toolchain (with the required
parameters) in that environment without impact on our build
infrastructure. The big advantage is that the complete toolchain
selection (CPU,ABI etc) only needs to be done in buildroot.

>
>> If you look to the changes I made to the wrapper, you can see that a
>> completely different set of options can be passed to the linker. The
>> compiler options are passed to the compiler while a different set of
>> options is passed to the linker.
>
>
>  Sorry, I didn't look at the patch in that much detail...
>
>
>
>  Regards,
>  Arnout
> --
> Arnout Vandecappelle                               arnout at mind be
> Senior Embedded Software Architect                 +32-16-286540
> Essensium/Mind                                     http://www.mind.be
> G.Geenslaan 9, 3001 Leuven, Belgium                BE 872 984 063 RPR Leuven
> LinkedIn profile: http://www.linkedin.com/in/arnoutvandecappelle
> GPG fingerprint:  7CB5 E4CC 6C2E EFD4 6E3D A754 F963 ECAB 2450 2F1F