.so dlopen(), dlsym() and functions in main() executable

For a dynamic library .so file , we can use dlopen(), dlsym() to call  functions inside a .so file.

Can the functions in .so call functions in main() executable? Most of the time it works, but not always. It's not very reliable.

A reliable way to let functions in .so call functions in main() executable is to save the fucntion address as a struct, and pass it to a .so initial function and .so save it.

to check external reference functions in .so, use 'nm file.so' . The functions with 'U'  are undefined external functions.

$nm xxxx.so

00004daa t disp_select
0000a9e4 b dtor_idx.6973
0000aa10 b event_box_anthy

0000aa10 b event_box_anthy
         U exit@@GLIBC_2.0
00004290 t frame_dummy
         U g_signal_connect_data