If you want to use dlopen() to open a C++ shared library from a C program, make sure that the shared library has a dependency on the appropriate C++ runtime (libCrun.so.1 for -compat=5).
To do this, add -lCrun for -compat=5 to the command line when building the shared library. For example:
example% CC -G -compat=5... -lCrun
When using -compat=g, -std=c++03 or -std=c++11 options, you need to link the g++ support libraries instead:
example% CC -G -std=c++11 ... -lstdc++ -lgcc_s -lCrunG3
If the shared library uses exceptions and does not have a dependency on the C++ runtime library, your C program might behave erratically.