On some operating systems, a program symbol must be specially declared
in order to be dynamically resolved with the dlsym (or
equivalent) function. Libtool provides the -export-dynamic and
-module link flags (see Link mode), for you to make that
declaration. You need to use these flags if you are linking an
application program that dlopens other modules or a libtool library
that will also be dlopened.
For example, if we wanted to build a shared library, hello, that would later be dlopened by an application, we would add -module to the other link flags:
burger$ libtool --mode=link gcc -module -o hello.la foo.lo \
hello.lo -rpath /usr/local/lib -lm
burger$
If symbols from your executable are needed to satisfy unresolved references in a library you want to dlopen you will have to use the flag -export-dynamic. You should use -export-dynamic while linking the executable that calls dlopen:
burger$ libtool --mode=link gcc -export-dynamic -o helldl main.o burger$