随手记

If your project is linked with "-nostdlib -Wl,--no-undefined", you need to provide
your own __dso_handle because crtbegin_so.o isn't linked. The content of __dso_handle
doesn't matter. eg.

extern "C" {
extern void *__dso_handle __attribute__((__visibility__ ("hidden")));
void *__dso_handle;
}