Avoid exporting of internal symbols

[Satz Klauer]

I'm creating a shared library using libtool:

libtool --mode=compile g++ -Wall -fPIC -shared -Wno-unused
-Wno-unused-result $(CFLAGS) $(LFLAGS)
libtool --mode=link g++ -shared -export-symbols-regex mylib_ -rpath
/usr/lib $(LFLAGS)

(That's a snipped only, there of course is the part that causes
compilation of sources).

As far as I understood it, the statement "-export-symbols-regex
mylib_" should ensure only functions starting with "mylib_" should be
exported by the resulting library. But when I check the resulting
.so-file it contains all symbols and names that are used within the
sources. Independent if the symbols are private or internal-only, if
they are whole class-names or simple functions, I can see all of them
within the library. The same happens when I use "-export-symbols"
together with a symbol file instead, it seems like the symbol
definitions are ignored completely.

So my question: how can I avoid that? How can I strip the library
completely to have only these functions exported and visible that are
really allowed to be called by programs that make use of my library?
That's important for two reasons: I want to save binary code size and
(even more important) avoid users are calling functions/using objects
that are not intended for external usage.

Thanks!