[Buildroot] external toolchains and sysroot

[Jean-Mickael Guerin <jean-mickael.guerin@6wind.com>]

On 19/10/2012 12:02, Richard Braun wrote:
> On Fri, Oct 19, 2012 at 11:57:30AM +0200, Richard Braun wrote:
>> On Fri, Oct 19, 2012 at 11:46:10AM +0200, Jean-Mickael Guerin wrote:
>>> I would expect the wrapper the use -I and -L to help the lookup of
>>> headers and libraries installed afterwards. Why --sysroot?
>>
>> -I and -L extend the default list of search directories whereas
>> --sysroot replaces them. This completely avoids using native libraries
>> by mistake.
>
> I might have answered a bit fast. I suppose what you have in mind is let
> the toolchain use its own sysroot, defined at compile time (when the
> toolchain was built) and then extend it with -I and -L. The problem with
> this is that it would force everyone to use the very same path for one
> toolchain, which can be tedious for external toolchains (you might have
> several with the same built-in sysroot).
>
Not exactly: let the toolchain use its own sysroot, and use -I /-L to 
look up in the staging directory. Original sysroot is read-only & 
shared, staging belongs to your build directory.

In another words my point is that the copy of sysroot is useless,
using --sysroot=<my copy of built-in sysroot path, computed from the 
toolchain's compiler> cannot be safer than let it use the built-in syroot.
Removing this copy will save time, space, and compatible whatever the 
directory layout of the toolchain.