[LLVMdev] Why is BasicBlock's copy constructor private?

[Trevor Harmon]

Hi,

LLVM provides basic graph traversal for its CFGs, but I need  
additional operations, such as iterating over the edges. I thought I  
would solve this problem using the Boost graph library. It should be  
relatively simple to walk an LLVM CFG and add the BasicBlock objects  
to a Boost graph declared as:

    typedef boost::directed_graph<llvm::BasicBlock> Graph;

Once constructed, this automatically gives me access to all kinds of  
sophisticated graph routines.

Unfortunately, the above code doesn't compile because Boost apparently  
needs the class to have a copy constructor, and BasicBlock's copy  
constructor is private. From BasicBlock.h:

class BasicBlock : ... {
private:
   ...
   BasicBlock(const BasicBlock &);     // Do not implement
   void operator=(const BasicBlock &); // Do not implement
   ...
}

This causes a slew of errors related to Boost trying to call the copy  
constructor and failing. Making the copy constructor public causes the  
errors to disappear.

So why exactly is BasicBlock's copy constructor private? The ominous  
"Do not implement" warning leads me to think there is some sort of  
design issue that is preventing a copy constructor here. Is there any  
possibility of working around it?

Thanks,

Trevor