gcc/ld: what is to -Wl,-rpath in dynamic linking what -l is to -L in static linking?

Question

With /my/dir/path/foo.a and /my/dir/path/bar.a:

To statically link using gcc/g++, one uses -L to specify the directory containing the static libraries and -l to specify the name of the library. In this case one would write gcc -L/my/dir/path -lfoo -lbar ....

With /my/dir/path/foo.so and /my/dir/path/bar.so:

To dynamically link using gcc/g++, one uses -Wl,-rpath,/my/dir/path. How are the names of the libraries specified? Is the command gcc -L/my/dir/path -Wl,-rpath,/my/dir/path -lfoo -lbar ... correct? Or should it be gcc -L/my/dir/path -Wl,-rpath,/my/dir/path -Wl,-lfoo -Wl,-lbar ...? In other words, do the library names need to be passed on to the linker through -Wl,-l?

Answer 1

The -l argument works well for both static and shared libraries but expects the filename of specified library to be in a specific format. Namely, -lfoo tells the linker to look for a file named libfoo.a or libfoo.so. If you want to links against a library whose filename don't have this 'lib' prefix (i. e. foo.so), you can use a semicolon and specify a filename: -l:foo.so.

So, to dynamically link against /my/dir/path/foo.so and /my/dir/path/bar.so you need to issue the following command:

g++ -L/my/dir/path/ -l:foo.so -l:bar.so

As for -rpath, it has the -rpath=<path> format, so in order to pass it to the linked you need the issue the following:

g++ -L/my/dir/path/ -Wl,-rpath=/my/dir/path/ -l:foo.so -l:bar.so