OSX Xcode - Packaging dependencies libmysqlclient.18.dylib

Question

This may well have been asked before I just couldn't figure out the right term to search.

I'm writing a client-server application to run on an OSX desktop which will talk to a MySQL server on the local network. It seems long-winded to implement a web-services API when basically a bunch of SQL statements will be perfect internally.

I've wrestled with the install procedure for MySQL server on my development machine, ad had to resort to symlinking libmysqlclient.18.dylib into /usr/lib even though i'd put the include path in header search paths.

What I need to know is how do I create a .app file I can send to other machines that will have access to the libmysqlclient.18.dylib file?

I'm used to Windows having installers to do this and a bit new to OSX programming although i've been doing Obj-c for iDevices for 2 years.

Is there a setting which allows the library to be copied into the .app file or do I need to install the mysql connector on each machine - if so, how do I get around the symlink issue, ideally I need it to work from the stock folders.

If this has been answered somewhere else, please point me in the right direction.

Answer 1

At build time the static linker on OS X, ld, writes the shared library identifier of each library that your application links against in to the application binary. At run time the dynamic linker, dyld, attempts to load each shared library from the paths specified in the application binary. You can see this information using otool -L YourApp.app/Contents/MacOS/YourApp.

The fact you needed to symlink libmysqlclient.18.dylib in to /usr/lib suggests that the shared library identifier of libmysqlclient.18.dylib is something like /usr/lib/libmysqlclient.18.dylib. To include the library in your .app bundle in a way that your application will use it rather than looking in /usr/lib you need to:

1. Change the shared library identifier of libmysqlclient.18.dylib so that dyld will look for the binary relative to your application binary. This is typically done by running install_name_tool -id @executable_path/../Frameworks/libmysqlclient.18.dylib libmysqlclient.18.dylib.

2. Copy the modified libmysqlclient.18.dylib in to the Frameworks subdirectroy in your application bundle. This is typically done using a Copy Files build phase in your Xcode project.

You should then be able to verify that the install name written in to your application binary is @executable_path/../Frameworks/libmysqlclient.18.dylib rather than /usr/lib/libmysqlclient.18.dylib (using otool -L YourApp.app/Contents/MacOS/YourApp again). If the install name isn't correct then you'll need to ensure that your linker search path is set up to find your modified version of libmysqlclient.18.dylib ahead of any other versions you may have.