Linker and Libraries Guide

Dependencies Between Unbundled Products

The next issue to confront dependency location is how to establish a model whereby one unbundled product might have dependencies on the shared objects of another unbundled product.

For example, the unbundled product XYZ might have dependencies on the product ABC. This dependency can be established by a host package installation script that generates a symbolic link to the installation point of the ABC product:

Figure C-2 Unbundled Co-dependencies

The binaries and shared objects of the XYZ product can represent their dependencies on the ABC product using the symbolic link as a stable reference point. For the application xyz this would be:

% dump -Lv xyz
  [1]   NEEDED  libX.so.1
  [2]   NEEDED  libA.so.1
  [3]   RPATH   $ORIGIN/../lib:$ORIGIN/../ABC/lib

and similarly for the dependency libX.so.1 this would be

% dump -Lv libX.so.1
  [1]   NEEDED  libY.so.1
  [2]   NEEDED  libC.so.1
  [3]   RPATH   $ORIGIN:$ORIGIN/../ABC/lib

Therefore, if this product is now installed under /usr/local/XYZ, its post-install script would be required to establish a symbolic link of:

% ln -s ../ABC /usr/local/XYZ/ABC

If the user's PATH is augmented with /usr/local/XYZ/bin, then invocation of the application xyz will result in a pathname lookup for its dependencies as follows:

% ldd -s xyz
     find library=libX.so.1; required by xyz
      search path=$ORIGIN/../lib:$ORIGIN/../ABC/lib  (RPATH from file xyz)
      trying path=/usr/local/XYZ/lib/libX.so.1
        libX.so.1 =>     /usr/local/XYZ/lib/libX.so.1
 
     find library=libA.so.1; required by xyz
      search path=$ORIGIN/../lib:$ORIGIN/../ABC/lib  (RPATH from file xyz)
      trying path=/usr/local/XYZ/lib/libA.so.1
      trying path=/usr/local/ABC/lib/libA.so.1
        libA.so.1 =>     /usr/local/ABC/lib/libA.so.1
 
     find library=libY.so.1; required by /usr/local/XYZ/lib/libX.so.1
      search path=$ORIGIN:$ORIGIN/../ABC/lib \
                (RPATH from file /usr/local/XYZ/lib/libX.so.1)
      trying path=/usr/local/XYZ/lib/libY.so.1
        libY.so.1 =>     /usr/local/XYZ/lib/libY.so.1
 
     find library=libC.so.1; required by /usr/local/XYZ/lib/libX.so.1
      search path=$ORIGIN:$ORIGIN/../ABC/lib \
                (RPATH from file /usr/local/XYZ/lib/libX.so.1)
      trying path=/usr/local/XYZ/lib/libC.so.1
      trying path=/usr/local/ABC/lib/libC.so.1
        libC.so.1 =>     /usr/local/ABC/lib/libC.so.1
 
     find library=libB.so.1; required by /usr/local/ABC/lib/libA.so.1
       search path=$ORIGIN  (RPATH from file /usr/local/ABC/lib/libA.so.1)
       trying path=/usr/local/ABC/lib/libB.so.1
        libB.so.1 =>     /usr/local/ABC/lib/libB.so.1