[CMake] linking with .so w/ non-standard names

[Brad King]

Bill Hoffman wrote:
> So, it must be that the library is built with no soname.   Brad will be
> back in a few days, and should have a better idea of how to fix it.

This is probably the problem.  You can confirm this by running

  readelf -d /home/kchang/sandbox/thost/thostmduserapi.so |grep SONAME

If a line like this:

  0x000000000000000e (SONAME)             Library soname: [...]

does not appear then there is no soname.

> For now, you can do one of these:
> 
> 1. rename the library to have lib in front of it  libthostmduserapi.so

...or create a symlink to it with that name and give the full
path to the symlink to CMake.

> 2. Rebuild thostmduserapi.so with an soname

This is the best fix.  Shared libraries should always have the
soname field set because that is how the runtime linker is supposed
to locate the library.

I would be interested in an explanation from the authors of that
library as to why it has no 'lib' prefix or soname.

> 3. Add this to your CMakeLists.txt file:
> 
> set(CMAKE_PLATFORM_USES_PATH_WHEN_NO_SONAME FALSE)
> 
> before the target_link_library call. But, that might have some bad rpath
> information.

It will work but the resulting binary will only run on the machine
where it is built and always use thostmduserapi.so from that full
path.

4.) You can also tell CMake to use the full path by creating
an IMPORTED target for the library:

  add_library(thostmduserapi SHARED IMPORTED)
  set_property(TARGET thostmduserapi PROPERTY
    IMPORTED_LOCATION /home/kchang/sandbox/thost/thostmduserapi.so)
  target_link_libraries(myexe thostmduserapi)

Now CMake will use the full path, but the restrictions on running
the result will be the same as option #3 above.

-Brad