gistfile1.cpp

void x() {
  SomeClass blah;
  asyncthread(y(blah));
}

// Note if you pass shit by reference, it should be a const reference. Otherwise just use a pointer
void y(const SomeClass &blah) {
  Blah blah_copy(blah); // <-- assuming the constructor does not do a shallow copy
}

// This is how I'd design it

void x() {
  shared_ptr<SomeClass> blah(new SomeClass);
  asyncthread(y(blah)));
}

void y(const shared_ptr<SomeClass> &blah) {
  doShit(*blah);
}