Cross-compiling with nfs-mount as sysroot fails due to absolute links

Question

I want to cross-compile C++-applications for the raspi using the rpi-tools, CMake and a raspbian sysroot I'm exporting via nfs from a running raspi. My CMake-toolchain-file is OK, header-files and most of the libraries are correctly detecting inside my sysroot-mount.

Except that there is one issue which seems to be new with raspbian stretch?

The problem I'm facing is that the some library-files located at /usr/lib/arm-linux-gnueabihf/ are a link to the real file located at /lib/arm-linux-gnueabihf/. This link is done with an absolute path.

This is a problem when using the sysroot-mount via NFS (my moint-point is /mnt/rpi-rootfs). But this will also be a problem when doing cross-compilation with a copy of sysroot if sysroot contains links like that.

My CMakeFiles are looking for rt for example and as librt is linked to /lib/arm-linux-gnueabihf/librt.so.1. This file does not exist (it is actually located in /mnt/rpi-rootfs/lib/arm-linux-gnueabihf/librt.so.1) cmake fails.

Where is my mistake? Is there something I can do with the raspbian-distribution? Is this a bug? Is it a feature?

Answer 1

As a workaround I used symlinks to correct it:

cd /usr/lib/arm-linux-gnueabihf
symlinks -c .

absolute: /usr/lib/arm-linux-gnueabihf/libanl.so -> /lib/arm-linux-gnueabihf/libanl.so.1
changed:  /usr/lib/arm-linux-gnueabihf/libanl.so -> ../../../lib/arm-linux-gnueabihf/libanl.so.1
[..]

Previous answer: realpath doesn't work as expected, it adds a ../ too much.

I created a small script which replaces absolute links with relative ones in the current-directory.

#!/bin/bash

for L in $(find -type l)
do
    ABSOLUTE=$(readlink $L)

    if [[ $ABSOLUTE =~ ^/ ]] # if it starts with a / it is an absolute link
    then
        RELATIVE=$(realpath --relative-to=$L -s $ABSOLUTE)
        echo fixing link of $L to $ABSOLUTE with $RELATIVE
        sudo ln -sf $RELATIVE $L
    fi
done