Comment on Comments

OK:

if (vars.empty()) { 
  // Store null env pointer if environment is empty 
  builder.CreateStore(
      llvm::ConstantPointerNull::getNullValue( 
          clo_env_slot->getType()
             ->getContainedType(0)), 
      clo_env_slot, 
      /* isVolatile= */ false);
}

 

Better:

if (vars.empty()) {
  storeNullPointerToSlot(clo_env_slot);
}