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Comment by bunderbunder | Hacker News Reader

This seems easier in both Windows and OS X. On both, a native application gets its own directory, and will first look in there for any shared libraries it needs. It gives you a nice middle ground between static linking everything and dynamic linking everything that still avoids the "we have to choose between pervasive system-wide dependency hell and Dockerizing everything" situation that seems to exist on Linux.

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True for Windows, but not true for macOS. See DYLD_FALLBACK_LIBRARY_PATH in https://www.unix.com/man-page/osx/1/dyld/ -- the dynamic linker will look for the library at the proposed absolute or macro-expanded path (specified in the load command), and failing that look for the leaf name under a few fallback paths:

$(HOME)/lib:/usr/local/lib:/lib:/usr/lib

You'll notice that those fallback paths do not include any location relative to the application. It's actually pretty difficult to get the object code to lookup libraries relative to its own directory. Explanation here:

https://birchlabs.co.uk/blog/alex/juicysfplugin/synth/cpp/20...

That's not quite correct.

The program sets LD_RUNPATH_SEARCH_PATHS which bakes a list of paths into the binary. This can include relative paths as well as @loader_path and @executable_path. eg a plugin bundled with an app can specify @executable_path/../../Frameworks to reference the parent bundle's Frameworks directory. Libraries can also add search paths to help locate their dependencies. @loader_path will expand relative to the library that actually has the dependency.

Any linked library with a DYLD name of @rpath/ will be searched in those locations.

At build time the linker checks each library for its DYLD name and bakes that name into the final binary. Making sure all of your non-system dependencies are @rpath and relative to your app bundle is what makes it a "Relocatable" application.

Out of curiosity, what stopped you from setting the -install_name flag when you built the libraries you are bundling with your juicysfplugin plugin? That's the standard mechanism for building app-relative libraries and wasn't listed at all under "Alternatives to manually rewriting dynamic links"

@rpath is pretty standard. It works on both macOS and Linux, although many of the details are different.

"It's actually pretty difficult to get the object code to lookup libraries relative to its own directory."

One could just use a wrapper script that sets the DYLD_FALLBACK_LIBRARY_PATH relative to the binary's directory and run it.

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