Changing the CHOST variable

This document explains how to change the CHOST variable of an existing system.

Introduction
Changing the CHOST is a big issue that can seriously screw up a system - so why is there a guide for that if it can cause that much havoc?

There are certain situations where changing the  variable is inevitable, e.g. when upgrading to glibc 2.4 which only supports nptl and the user finds out that the current   is i386, which makes it impossible to use nptl. In this case, there are not a lot of options, and changing  is one of them.

Even after following these instructions, problems may arise, so please make sure to read and execute them very carefully. In this example the  variable will be changed from i386 to i686. Please change the commands according to the personal situation.

Building the packages
To start out with the  variable change, edit the  file and change the   value to suit the requirements. Then, rebuild the following packages in this order:

Verifying things work
Now it is time to make sure that the gcc-config and binutils-config settings are sane and that there are no leftovers in.

The output of gcc-config and binutils-config should look like the following:

Next, check to see if there are references to the old  variable in :

Before deleting the file, let's check for files with the updated  value:

This one looks good as there should always be only one file for  in  ( in this example), so delete the one with the wrong references:

The same also applies to binutils - if there's an extra one, see which is the outdated one and delete it. Next, check the contents of :

That one looks good, those two files should be there. Time to move on to the directory.

and are fine, but  is another leftover that needs removal.

Now run the following commands to update the environment:

Next, verify everything is fixed:

If there are still files found, try to track it down before going on.

Finishing The Change
Now it is necessary to re-emerge libtool and run fix_libtool_files.sh which can be found in. Make sure to use the correct gcc version (the current one, 4.1.1 here) and pass the old architecture (i386 here) as argument. Replace  with the new   value, and   with the gcc version. This example assumes a  value applicable to i686.

It is now possible to rebuild all the packages:

In theory, it should not be necessary to do so, but it can not be 100% guaranteed that this is actually the case.

The following set of packages really need to be rebuilt:

All packages using perl install to the  directory and hence need rebuilding. In case qfile is not available on the system yet, install first.

Now rebuild all packages that have files installed in any location:

When encountering other packages that need recompiling, please let us know through the |discussion page of this guide.

Common problems
When upgrading from gcc 3.3 to 4.1 at the same time as changing the  variable (please don't do that anyway), a couple of users reported broken packages that need recompiling, such as groff</tt> and courier</tt>:

This happens because during the upgrade, the  variable doesn't exactly match the   variable value, making the compiler assume that the system is using cross-compiling. As a consequence,  isn't inserted into, resulting in this error.

Please see the GCC upgrade guide for what needs to be rebuilt after a GCC upgrade.

In some rare cases, this can break old versions of python, too. This may be fixed by adding (change accordingly to the old   and gcc version) to, running ldconfig and then emerge libstdc++-v3. However, as can be seen, this situation needs to be avoided - don't change  and gcc at the same time.

Feedback
That should be all, feedback (both if it worked, failed or other problems were encountered) is welcome, please use the |discussion page or post to this forum thread. Much in this guide comes from vapier, thanks for your help!