Re: [PATCHv2 3/3] perf: add helper makefile for cross compiling libs

[Ingo Molnar <mingo@kernel.org>]

* Rabin Vincent <rabin.vincent@axis.com> wrote:

> On Thu, Oct 29, 2015 at 10:46:49AM +0100, Ingo Molnar wrote:
> > Would it be possible to add a gcc and glibc building portion as well? That would 
> > make it entirely self-hosting.
> 
> Yes, but:
> 
> - Those that intend to run the built binary on a target would presumably
>   already have a cross-compiler lying around which they use to build the
>   rest of userspace.
> 
> - Those that don't have a cross-compiler or need a newer one can already
>   very easily create one using other specialized tools such as
>   crosstool-ng (see below).



> 
> > 
> > Something like:
> > 
> >     make ARCH=arm BOOTSTRAP=1
> > 
> > ... would magically fetch everything needed, and (given enough Internet bandwidth 
> > and a fast enough machine) build a whole cross-environment from scratch.
> 
> This is already possible using crosstool-ng.  Getting an ARM GCC 5.2
> cross-compiler is as simple as:
> 
>  $ git clone git://crosstool-ng.org/crosstool-ng
>  $ cd crosstool-ng
>  $ ./bootstrap && ./configure --enable-local && make
> 
>  $ ./ct-ng arm-unknown-linux-gnueabi
>  $ ./ct-ng build

My point is, that's 5 non-trivial steps harder than just typing:

     make ARCH=arm BOOTSTRAP=1

> This is also possible with crosstool-ng. You just need to build the
> x86_64-unknown-linux-gnu config to get GCC 5.2 + glibc 2.22 toolchain
> for an x86-64 host.

It's also possibly by directly cloning the repos of those tools and building them 
- they are reasonably easy to build.

My point is that if we add automation, we might as well walk to whole mile.

Thanks,

	Ingo