File.........: 5 - Using the toolchain.txt
Copyrigth....: (C) 2010 Yann E. MORIN <yann.morin.1998@anciens.enib.fr>
License......: Creative Commons Attribution Share Alike (CC-by-sa), v2.5


Using the toolchain  /
____________________/


Using the toolchain is as simple as adding the toolchain's bin directory in
your PATH, such as:
  export PATH="${PATH}:/your/toolchain/path/bin"

and then using the target tuple to tell the build systems to use your
toolchain:
  ./configure --target=your-target-tuple
or
  make CC=your-target-tuple-gcc
or
  make CROSS_COMPILE=your-target-tuple-
and so on...

It is strongly advised not to use the toolchain sysroot directory as an
install directory for your programs/packages. If you do so, you will not be
able to use your toolchain for another project. It is even strongly advised
that your toolchain is chmod-ed to read-only once successfully build, so that
you don't go polluting your toolchain with your programs/packages' files.

Thus, when you build a program/package, install it in a separate directory,
eg. /your/root. This directory is the /image/ of what would be in the root file
system of your target, and will contain all that your programs/packages have
installed.


The 'populate' script |
----------------------+

When your root directory is ready, it is still missing some important bits: the
toolchain's libraries. To populate your root directory with those libs, just
run:
  your-target-tuple-populate -s /your/root -d /your/root-populated

This will copy /your/root into /your/root-populated, and put the needed and only
the needed libraries there. Thus you don't polute /your/root with any cruft that
would no longer be needed should you have to remove stuff. /your/root always
contains only those things you install in it.

You can then use /your/root-populated to build up your file system image, a
tarball, or to NFS-mount it from your target, or whatever you need.

The populate script accepts the following options:

 -s src_dir
    Use 'src_dir' as the un-populated root directory.

 -d dst_dir
    Put the populated root directory in 'dst_dir'.

 -l lib1 [...]
    Always add specified libraries.

 -L file
    Always add libraries listed in 'file'.

 -f
    Remove 'dst_dir' if it previously existed; continue even if any library
    specified with -l or -L is missing.

 -v
    Be verbose, and tell what's going on (you can see exactly where libs are
    coming from).

 -h
    Print the help.

See 'your-target-tuple-populate -h' for more information on the options.

Here is how populate works:

  1) performs some sanity checks:
     - src_dir and dst_dir are specified
     - src_dir exists
     - unless forced, dst_dir does not exist
     - src_dir != dst_dir

  2) copy src_dir to dst_dir

  3) add forced libraries to dst_dir
     - build the list from -l and -L options
     - get forced libraries from the sysroot (see below for heuristics)
       - abort on the first missing library, unless -f is specified

  4) add all missing libraries to dst_dir
     - scan dst_dir for every ELF files that are 'executable' or
       'shared object'
     - list the "NEEDED Shared library" fields
       - check if the library is already in dst_dir/lib or dst_dir/usr/lib
       - if not, get the library from the sysroot
         - if it's in sysroot/lib, copy it to dst_dir/lib
         - if it's in sysroot/usr/lib, copy it to dst_dir/usr/lib
         - in both cases, use the SONAME of the library to create the file
           in dst_dir
         - if it was not found in the sysroot, this is an error.
