For passers-by: Linux has static libs as .a files, indexed ar archives with object files in them, and ELF shared objects as .so shared libraries. In AIX, .a ar archives may hold object files to be static libs, they may hold shared objects to be treated as a shared library (a lot of shared libraries on AIX are .a files rather than .so), and they may hold both 64 and 32 bit files of each to support multiple architectures. A single .a file can be a 32 bit static library, a 64 bit static library, a 32 bit shared library, and a 64 bit shared library all in one.
It has some convenience, in that all the different types of libraries for a package can be found in one place, but I've always found it annoying, especially when you have very specific goals to accomplish and need some libraries linked statically and others dynamically.
C++ is not by best friend by far, but I'm happy to gain any convenience and safety where I can get it in the language that I use regularly.