[RFC] Kbuild: allow code re-use across different directories

[Arnaud Lacombe]

Hi,

On Thu, Sep 8, 2011 at 4:33 PM, Nicolas Pitre <nico at fluxnic.net> wrote:
> On Thu, 8 Sep 2011, Arnaud Lacombe wrote:
>
>> you missed:
>>
>>  # Make sure files are removed during clean
>> -extra-y       += piggy.gzip piggy.lzo piggy.lzma lib1funcs.S
>> +extra-y       += piggy.gzip piggy.lzo piggy.lzma
>>
>> This confused make.
>
> Well... that was suttle.
>
he, welcome to make(1) world :)

> So yes, your patch may certainly be useful to a couple cases, and it
> works fine for this lib1func.S.
>
> It doesn't help me much in the following situation though.  What I
> actually want to achieve is to compile arch/arm/boot/compressed/fdt_rw.o
> from scripts/dtc/libfdt/fdt_rw.c, however I want it to include my local
> version of libfdt_env.h rather than scripts/dtc/libfdt/libfdt_env.h.  I
> still haven't found a way to convince gcc to do that.
>
The only choice you have in gcc, is to use -I-, to construct:

 $(CROSS_COMPILE)gcc -I$(srctree)/arch/arm/boot/compressed -I- [...]

however, it's been marked as deprecated, but still usable as of today
snapshot of 4.7.0. Its replacement, -iquote, do not provide this
functionnality, that is to override the source file origin directory
as search directory for #include "...".

 - Arnaud


> Nicolas
>