Forcing RPATH Embedding in Debian Packages

When building packages using the Bloom packaging process with CMake, you may encounter issues with RPATH embedding. Specifically, the installed executable may not include the required RPATH information, leading to dynamic library resolution failures.

In this scenario, we will explore ways to force the inclusion of RPATH into the executable during the Debian package generation process.

Understanding RPATH

RPATH is a mechanism used by CMake to specify the directory where libraries and executables can be found. It allows for more flexibility when building projects that rely on external dependencies. However, in some cases, RPATH may not be embedded correctly, leading to issues with dynamic library resolution.

CMake Configuration

To ensure that the RPATH is included in the executable during the build process, you can set the `CMAKE_BUILD_WITH_INSTALL_RPATH` variable to FALSE. This will prevent CMake from using the install RPATH and instead use the full RPATH for the build tree.

```cmake

SET(CMAKE_BUILD_WITH_INSTALL_RPATH FALSE)

```

Always Full RPATH

The Always Full RPATH section in your CMake configuration file can also be used to achieve the desired behavior. This section specifies that the full RPATH should always be included in the executable, regardless of whether it is being built for installation or not.

```cmake

# Always use the full RPATH

SET(CMAKE_BUILD_WITH_INSTALL_RPATH FALSE)

SET(CMAKE_USE_FULL_RPATH TRUE)

```

readelf Output

The output of `readelf -d` on a Debian package without RPATH and another version with RPATH included can help illustrate the issue:

```bash

$ readelf -d /opt/ros/kinetic/lib/pi_sonar/pi_sonar

Tag Type Name/Value

x00000001 (NEEDED) Shared library: 'libboost_thread.so.1'

x0000000f (RPATH) Library rpath: '/opt/ros/kinetic/lib'

```

Forcing RPATH Embedding

In the case where the executable is not including RPATH information, you can use `patchelf` to manually set the RPATH. This will allow the executable to resolve dynamic libraries correctly.

```bash

sudo patchelf -force-rpath -set-rpath '/opt/ros/kinetic/lib/' /opt/ros/kinetic/lib/pi_sonar/pi_sonar

```

In conclusion, forcing RPATH embedding in Debian packages generated using the Bloom packaging process can be achieved by setting `CMAKE_BUILD_WITH_INSTALL_RPATH` to FALSE and enabling Always Full RPATH. Additionally, manually setting the RPATH using `patchelf` can also resolve issues with dynamic library resolution. By following these steps, you should be able to ensure that your ROS node runs correctly even when built as setuid.

Cmake install rpath