Set a Shared Library Search Path in a Lazarus Linux Project

2 min
Notes

I was helping a friend build a Linux client for MeFrp with Lazarus and Qt 5. The application depends on libQt5Pas, and asking every user to install a compatible copy system-wide was not ideal. I wanted to ship the library in the same directory as the executable.

In a Lazarus community group, one suggestion was to put libQt5Pas in a system library directory such as /lib. Another person pointed out that the linker can be given a library search path, but could not remember the exact option. I eventually asked on the Lazarus forum: Specify the path to libQt5Pas on Linux.

Lazarus project compilation and linking options

Add an rpath

In the project options, open Compiler Options → Compilation and Linking and add this linker option, replacing the placeholder with the directory that contains the shared library:

-rpath <directory-containing-the-shared-library>

Adding an rpath to the Lazarus project linker options

Rebuild the project. The runtime linker uses an embedded rpath when searching for shared libraries. This example uses a fixed directory; for a portable bundle with the .so beside the executable, GNU ld also supports the $ORIGIN token. Check the resulting ELF metadata with readelf -d before distributing the application, and make sure the library is compatible with the target system.

This technique is for Linux/ELF executables. It does not replace packaging a compatible shared library or satisfy that library’s own dependencies. See the GNU ld documentation for -rpath.

If Lazarus is not installed yet, see the Linux Lazarus setup note in the Chinese version of this blog.

This note was restored from the Wayback Machine on April 11, 2024.

Series: Free Pascal and Lazarus