diff --git a/include/blocks/block.h b/include/blocks/block.h
index 6bcf46d..9830379 100644
--- a/include/blocks/block.h
+++ b/include/blocks/block.h
@@ -29,6 +29,20 @@ std::shared_ptr<T> to(std::shared_ptr<block> p) {
 	return ret;
 }
 
+template <typename T>
+std::shared_ptr<T> clone(std::shared_ptr<T> p) {
+	if (!p) return nullptr;
+	return to<T>(p->clone_impl());
+}
+
+template <typename T>
+std::shared_ptr<T> clone_obj(T* t) {
+	auto np = std::make_shared<T>();
+	np->static_offset = t->static_offset;
+	np->metadata_map = t->metadata_map;
+	return np;
+}
+
 template <typename T>
 class block_metadata_impl;
 
@@ -62,6 +76,8 @@ class block_metadata_impl : public block_metadata {
 	block_metadata_impl(T _val) : val(_val) {}
 };
 
+
+
 class block : public std::enable_shared_from_this<block> {
 public:
 	virtual ~block() = default;
@@ -113,6 +129,11 @@ class block : public std::enable_shared_from_this<block> {
 			return false;
 		return true;
 	}
+
+	virtual block::Ptr clone_impl(void) {
+		// abstract class always returns nullptr
+		return nullptr;
+	}
 };
 } // namespace block
 #endif
diff --git a/include/blocks/expr.h b/include/blocks/expr.h
index 655d773..b24f07a 100644
--- a/include/blocks/expr.h
+++ b/include/blocks/expr.h
@@ -70,6 +70,23 @@ class binary_expr : public expr {
 		return binary_is_same(self<binary_expr>(), other);
 	}
 };
+
+
+template <typename T>
+std::shared_ptr<T> unary_clone_helper(T* t) {
+	auto np = clone_obj(t);
+	np->expr1 = clone(t->expr1);
+	return np;
+}
+
+template <typename T>
+std::shared_ptr<T> binary_clone_helper(T* t) {
+	auto np = clone_obj(t);
+	np->expr1 = clone(t->expr1);
+	np->expr2 = clone(t->expr2);
+	return np;
+}
+
 // For the logical not operator
 class not_expr : public unary_expr {
 public:
@@ -81,6 +98,9 @@ class not_expr : public unary_expr {
 	virtual bool is_same(block::Ptr other) override {
 		return unary_is_same(self<not_expr>(), other);
 	}
+	virtual block::Ptr clone_impl(void) override {
+		return unary_clone_helper(this);
+	}
 };
 // For the unary minus operator
 class unary_minus_expr : public unary_expr {
@@ -93,6 +113,9 @@ class unary_minus_expr : public unary_expr {
 	virtual bool is_same(block::Ptr other) override {
 		return unary_is_same(self<unary_minus_expr>(), other);
 	}
+	virtual block::Ptr clone_impl(void) override {
+		return unary_clone_helper(this);
+	}
 };
 // For the bitwise not operator
 class bitwise_not_expr : public unary_expr {
@@ -105,6 +128,9 @@ class bitwise_not_expr : public unary_expr {
 	virtual bool is_same(block::Ptr other) override {
 		return unary_is_same(self<bitwise_not_expr>(), other);
 	}
+	virtual block::Ptr clone_impl(void) override {
+		return unary_clone_helper(this);
+	}
 };
 
 class and_expr : public binary_expr {
@@ -117,6 +143,9 @@ class and_expr : public binary_expr {
 	virtual bool is_same(block::Ptr other) override {
 		return binary_is_same(self<and_expr>(), other);
 	}
+	virtual block::Ptr clone_impl(void) override {
+		return binary_clone_helper(this);
+	}
 };
 
 class bitwise_and_expr : public binary_expr {
@@ -129,6 +158,9 @@ class bitwise_and_expr : public binary_expr {
 	virtual bool is_same(block::Ptr other) override {
 		return binary_is_same(self<bitwise_and_expr>(), other);
 	}
+	virtual block::Ptr clone_impl(void) override {
+		return binary_clone_helper(this);
+	}
 };
 
 class or_expr : public binary_expr {
@@ -141,6 +173,9 @@ class or_expr : public binary_expr {
 	virtual bool is_same(block::Ptr other) override {
 		return binary_is_same(self<or_expr>(), other);
 	}
+	virtual block::Ptr clone_impl(void) override {
+		return binary_clone_helper(this);
+	}
 };
 
 class bitwise_or_expr : public binary_expr {
@@ -153,6 +188,9 @@ class bitwise_or_expr : public binary_expr {
 	virtual bool is_same(block::Ptr other) override {
 		return binary_is_same(self<bitwise_or_expr>(), other);
 	}
+	virtual block::Ptr clone_impl(void) override {
+		return binary_clone_helper(this);
+	}
 };
 
 class bitwise_xor_expr : public binary_expr {
@@ -165,6 +203,9 @@ class bitwise_xor_expr : public binary_expr {
 	virtual bool is_same(block::Ptr other) override {
 		return binary_is_same(self<bitwise_xor_expr>(), other);
 	}
+	virtual block::Ptr clone_impl(void) override {
+		return binary_clone_helper(this);
+	}
 };
 
 class plus_expr : public binary_expr {
@@ -177,6 +218,9 @@ class plus_expr : public binary_expr {
 	virtual bool is_same(block::Ptr other) override {
 		return binary_is_same(self<plus_expr>(), other);
 	}
+	virtual block::Ptr clone_impl(void) override {
+		return binary_clone_helper(this);
+	}
 };
 
 class minus_expr : public binary_expr {
@@ -189,6 +233,9 @@ class minus_expr : public binary_expr {
 	virtual bool is_same(block::Ptr other) override {
 		return binary_is_same(self<minus_expr>(), other);
 	}
+	virtual block::Ptr clone_impl(void) override {
+		return binary_clone_helper(this);
+	}
 };
 
 class mul_expr : public binary_expr {
@@ -201,6 +248,9 @@ class mul_expr : public binary_expr {
 	virtual bool is_same(block::Ptr other) override {
 		return binary_is_same(self<mul_expr>(), other);
 	}
+	virtual block::Ptr clone_impl(void) override {
+		return binary_clone_helper(this);
+	}
 };
 
 class div_expr : public binary_expr {
@@ -213,6 +263,9 @@ class div_expr : public binary_expr {
 	virtual bool is_same(block::Ptr other) override {
 		return binary_is_same(self<div_expr>(), other);
 	}
+	virtual block::Ptr clone_impl(void) override {
+		return binary_clone_helper(this);
+	}
 };
 class lt_expr : public binary_expr {
 public:
@@ -224,6 +277,9 @@ class lt_expr : public binary_expr {
 	virtual bool is_same(block::Ptr other) override {
 		return binary_is_same(self<lt_expr>(), other);
 	}
+	virtual block::Ptr clone_impl(void) override {
+		return binary_clone_helper(this);
+	}
 };
 class gt_expr : public binary_expr {
 public:
@@ -235,6 +291,9 @@ class gt_expr : public binary_expr {
 	virtual bool is_same(block::Ptr other) override {
 		return binary_is_same(self<gt_expr>(), other);
 	}
+	virtual block::Ptr clone_impl(void) override {
+		return binary_clone_helper(this);
+	}
 };
 class lte_expr : public binary_expr {
 public:
@@ -246,6 +305,9 @@ class lte_expr : public binary_expr {
 	virtual bool is_same(block::Ptr other) override {
 		return binary_is_same(self<lte_expr>(), other);
 	}
+	virtual block::Ptr clone_impl(void) override {
+		return binary_clone_helper(this);
+	}
 };
 class gte_expr : public binary_expr {
 public:
@@ -257,6 +319,9 @@ class gte_expr : public binary_expr {
 	virtual bool is_same(block::Ptr other) override {
 		return binary_is_same(self<gte_expr>(), other);
 	}
+	virtual block::Ptr clone_impl(void) override {
+		return binary_clone_helper(this);
+	}
 };
 class lshift_expr : public binary_expr {
 public:
@@ -268,6 +333,9 @@ class lshift_expr : public binary_expr {
 	virtual bool is_same(block::Ptr other) override {
 		return binary_is_same(self<lshift_expr>(), other);
 	}
+	virtual block::Ptr clone_impl(void) override {
+		return binary_clone_helper(this);
+	}
 };
 class rshift_expr : public binary_expr {
 public:
@@ -279,6 +347,9 @@ class rshift_expr : public binary_expr {
 	virtual bool is_same(block::Ptr other) override {
 		return binary_is_same(self<rshift_expr>(), other);
 	}
+	virtual block::Ptr clone_impl(void) override {
+		return binary_clone_helper(this);
+	}
 };
 class equals_expr : public binary_expr {
 public:
@@ -290,6 +361,9 @@ class equals_expr : public binary_expr {
 	virtual bool is_same(block::Ptr other) override {
 		return binary_is_same(self<equals_expr>(), other);
 	}
+	virtual block::Ptr clone_impl(void) override {
+		return binary_clone_helper(this);
+	}
 };
 
 class ne_expr : public binary_expr {
@@ -302,6 +376,9 @@ class ne_expr : public binary_expr {
 	virtual bool is_same(block::Ptr other) override {
 		return binary_is_same(self<ne_expr>(), other);
 	}
+	virtual block::Ptr clone_impl(void) override {
+		return binary_clone_helper(this);
+	}
 };
 
 class mod_expr : public binary_expr {
@@ -314,6 +391,9 @@ class mod_expr : public binary_expr {
 	virtual bool is_same(block::Ptr other) override {
 		return binary_is_same(self<mod_expr>(), other);
 	}
+	virtual block::Ptr clone_impl(void) override {
+		return binary_clone_helper(this);
+	}
 };
 class var_expr : public expr {
 public:
@@ -332,6 +412,13 @@ class var_expr : public expr {
 			return false;
 		return true;
 	}
+	virtual block::Ptr clone_impl(void) override {
+		auto np = clone_obj(this);
+		// Vars are special cases and should not be cloned
+		// This is to avoid problems where vars are compared by pointers
+		np->var1 = var1;
+		return np;	
+	}
 };
 
 class const_expr : public expr {
@@ -368,6 +455,12 @@ class int_const : public const_expr {
 			return false;
 		return true;
 	}
+	virtual block::Ptr clone_impl(void) override {
+		auto np = clone_obj(this);
+		np->value = value;
+		np->is_64bit = is_64bit;
+		return np;
+	}
 };
 class double_const : public const_expr {
 public:
@@ -387,6 +480,12 @@ class double_const : public const_expr {
 			return false;
 		return true;
 	}
+	virtual block::Ptr clone_impl(void) override {
+		auto np = clone_obj(this);
+		np->value = value;
+		return np;
+	}
+	
 };
 class float_const : public const_expr {
 public:
@@ -406,6 +505,11 @@ class float_const : public const_expr {
 			return false;
 		return true;
 	}
+	virtual block::Ptr clone_impl(void) override {
+		auto np = clone_obj(this);
+		np->value = value;
+		return np;
+	}
 };
 
 class string_const : public const_expr {
@@ -426,6 +530,11 @@ class string_const : public const_expr {
 			return false;
 		return true;
 	}
+	virtual block::Ptr clone_impl(void) override {
+		auto np = clone_obj(this);
+		np->value = value;
+		return np;
+	}
 };
 
 class assign_expr : public expr {
@@ -449,6 +558,12 @@ class assign_expr : public expr {
 			return false;
 		return true;
 	}
+	virtual block::Ptr clone_impl(void) override {
+		auto np = clone_obj(this);
+		np->var1 = clone(var1);
+		np->expr1 = clone(expr1);
+		return np;
+	}	
 };
 class sq_bkt_expr : public expr {
 public:
@@ -470,6 +585,12 @@ class sq_bkt_expr : public expr {
 			return false;
 		return true;
 	}
+	virtual block::Ptr clone_impl(void) override {
+		auto np = clone_obj(this);
+		np->var_expr = clone(var_expr);
+		np->index = clone(index);
+		return np;
+	}	
 };
 class function_call_expr : public expr {
 public:
@@ -496,6 +617,14 @@ class function_call_expr : public expr {
 		}
 		return true;
 	}
+	virtual block::Ptr clone_impl(void) override {
+		auto np = clone_obj(this);
+		np->expr1 = clone(expr1);
+		for (auto arg: args) {
+			np->args.push_back(clone(arg));
+		}
+		return np;
+	}	
 };
 
 class initializer_list_expr : public expr {
@@ -519,6 +648,13 @@ class initializer_list_expr : public expr {
 		}
 		return true;
 	}
+	virtual block::Ptr clone_impl(void) override {
+		auto np = clone_obj(this);
+		for (auto elem: elems) {
+			np->elems.push_back(clone(elem));
+		}
+		return np;
+	}
 };
 
 // We first implement a base class for foreign_expr for visitor purposes
@@ -558,6 +694,11 @@ class foreign_expr : public foreign_expr_base {
 			return false;
 		return true;
 	}
+	virtual block::Ptr clone_impl(void) override {
+		auto np = clone_obj(this);
+		np->inner_expr = inner_expr;
+		return np;
+	}
 };
 
 class member_access_expr : public expr {
@@ -580,6 +721,12 @@ class member_access_expr : public expr {
 			return false;
 		return true;
 	}
+	virtual block::Ptr clone_impl(void) override {
+		auto np = clone_obj(this);
+		np->parent_expr = clone(parent_expr);
+		np->member_name = member_name;
+		return np;
+	}
 };
 
 class addr_of_expr : public expr {
@@ -599,6 +746,11 @@ class addr_of_expr : public expr {
 			return false;
 		return true;
 	}
+	virtual block::Ptr clone_impl(void) override {
+		auto np = clone_obj(this);
+		np->expr1 = clone(expr1);
+		return np;
+	}
 };
 } // namespace block
 
diff --git a/include/blocks/stmt.h b/include/blocks/stmt.h
index a0403b5..c1f9794 100644
--- a/include/blocks/stmt.h
+++ b/include/blocks/stmt.h
@@ -19,6 +19,13 @@ class stmt : public block {
 	}
 };
 
+template <typename T>
+std::shared_ptr<T> clone_stmt(T* t) {
+	auto np = clone_obj(t);
+	np->annotation = t->annotation;
+	return np;
+}
+
 class expr_stmt : public stmt {
 public:
 	typedef std::shared_ptr<expr_stmt> Ptr;
@@ -41,6 +48,13 @@ class expr_stmt : public stmt {
 			return false;
 		return true;
 	}
+	virtual block::Ptr clone_impl(void) override {
+		auto np = clone_stmt(this);
+		np->expr1 = clone(expr1);
+		np->mark_for_deletion = mark_for_deletion;
+		return np;
+	}
+	
 };
 
 class stmt_block : public stmt {
@@ -65,6 +79,13 @@ class stmt_block : public stmt {
 		}
 		return true;
 	}
+	virtual block::Ptr clone_impl(void) override {
+		auto np = clone_stmt(this);
+		for (auto stmt: stmts) {
+			np->stmts.push_back(clone(stmt));
+		}
+		return np;
+	}
 };
 
 class decl_stmt : public stmt {
@@ -94,6 +115,17 @@ class decl_stmt : public stmt {
 			return false;
 		return true;
 	}
+	virtual block::Ptr clone_impl(void) override {
+		auto np = clone_stmt(this);
+		// Vars are not to be cloned because 
+		// they are compared by pointers sometimes
+
+		// If we _do_ end up duplicating them, 
+		// they should be consistently updated
+		np->decl_var = decl_var;
+		np->init_expr = clone(init_expr);
+		return np;
+	}
 };
 
 class if_stmt : public stmt {
@@ -132,6 +164,13 @@ class if_stmt : public stmt {
 			return true;
 		assert(false && "Statement unreachable");
 	}
+	virtual block::Ptr clone_impl(void) override {
+		auto np = clone_stmt(this);
+		np->cond = clone(cond);
+		np->then_stmt = clone(then_stmt);
+		np->else_stmt = clone(else_stmt);
+		return np;
+	}
 };
 class label : public block {
 public:
@@ -149,6 +188,11 @@ class label : public block {
 			return false;
 		return true;
 	}
+	virtual block::Ptr clone_impl(void) override {
+		// Don't duplicate labels
+		// just like vars these might be compared by ptr
+		return self<label>();
+	}
 };
 class label_stmt : public stmt {
 public:
@@ -167,6 +211,12 @@ class label_stmt : public stmt {
 			return false;
 		return true;
 	}
+	virtual block::Ptr clone_impl(void) override {
+		auto np = clone_stmt(this);
+		// Doesn't need to be duplicated
+		np->label1 = label1;
+		return np;
+	}
 };
 class goto_stmt : public stmt {
 public:
@@ -194,6 +244,12 @@ class goto_stmt : public stmt {
 		}
 		return true;
 	}
+	virtual block::Ptr clone_impl(void) override {
+		auto np = clone_stmt(this);
+		np->label1 = label1;
+		np->temporary_label_number = temporary_label_number;
+		return np;
+	}
 };
 class while_stmt : public stmt {
 public:
@@ -217,6 +273,12 @@ class while_stmt : public stmt {
 			return false;
 		return true;
 	}
+	virtual block::Ptr clone_impl(void) override {
+		auto np = clone_stmt(this);
+		np->body = clone(body);
+		np->cond = clone(cond);
+		return np;
+	}
 };
 class for_stmt : public stmt {
 public:
@@ -244,10 +306,17 @@ class for_stmt : public stmt {
 			return false;
 		return true;
 	}
+	virtual block::Ptr clone_impl(void) override {
+		auto np = clone_stmt(this);
+		np->decl_stmt = clone(decl_stmt);
+		np->cond = clone(cond);
+		np->update = clone(update);
+		np->body = clone(body);
+		return np;
+	}
 };
 class break_stmt : public stmt {
 public:
-	std::string type;
 	typedef std::shared_ptr<break_stmt> Ptr;
 	virtual void dump(std::ostream &, int) override;
 	virtual void accept(block_visitor *a) override {
@@ -258,6 +327,10 @@ class break_stmt : public stmt {
 			return false;
 		return true;
 	}
+	virtual block::Ptr clone_impl(void) override {
+		auto np = clone_stmt(this);
+		return np;
+	}
 };
 class continue_stmt : public stmt {
 public:
@@ -271,6 +344,10 @@ class continue_stmt : public stmt {
 			return false;
 		return true;
 	}
+	virtual block::Ptr clone_impl(void) override {
+		auto np = clone_stmt(this);
+		return np;
+	}
 };
 
 class func_decl : public stmt {
@@ -301,6 +378,16 @@ class func_decl : public stmt {
 			return false;
 		return true;
 	}
+	virtual block::Ptr clone_impl(void) override {
+		auto np = clone_stmt(this);
+		np->func_name = func_name;
+		np->return_type = clone(return_type);
+		for (auto arg: args) {
+			np->args.push_back(clone(arg));
+		}
+		np->body = clone(body);
+		return np;
+	}
 };
 
 class return_stmt : public stmt {
@@ -318,6 +405,11 @@ class return_stmt : public stmt {
 			return false;
 		return true;
 	}
+	virtual block::Ptr clone_impl(void) override {
+		auto np = clone_stmt(this);
+		np->return_val = clone(return_val);
+		return np;
+	}
 };
 } // namespace block
 #endif
diff --git a/include/blocks/var.h b/include/blocks/var.h
index 639bc04..f0baefb 100644
--- a/include/blocks/var.h
+++ b/include/blocks/var.h
@@ -17,6 +17,15 @@ class type : public block {
 	}
 	virtual void dump(std::ostream &, int) override;
 };
+
+template <typename T>
+std::shared_ptr<T> clone_type(T* t) {
+	auto np = clone_obj(t);
+	np->is_const = t->is_const;
+	np->is_volatile = t->is_volatile;
+	return np;	
+}
+
 class scalar_type : public type {
 public:
 	typedef std::shared_ptr<scalar_type> Ptr;
@@ -40,6 +49,12 @@ class scalar_type : public type {
 		a->visit(self<scalar_type>());
 	}
 	virtual void dump(std::ostream &, int) override;
+
+	virtual block::Ptr clone_impl(void) override {
+		auto np = clone_type(this);
+		np->scalar_type_id = scalar_type_id;
+		return np;
+	}
 };
 
 class pointer_type : public type {
@@ -50,6 +65,11 @@ class pointer_type : public type {
 		a->visit(self<pointer_type>());
 	}
 	virtual void dump(std::ostream &, int) override;
+	virtual block::Ptr clone_impl(void) override {
+		auto np = clone_type(this);
+		np->pointee_type = clone(pointee_type);
+		return np;
+	}
 };
 
 class reference_type : public type {
@@ -60,6 +80,11 @@ class reference_type : public type {
 		a->visit(self<reference_type>());
 	}
 	virtual void dump(std::ostream &, int) override;
+	virtual block::Ptr clone_impl(void) override {
+		auto np = clone_type(this);
+		np->referenced_type = clone(referenced_type);
+		return np;
+	}
 };
 
 class function_type : public type {
@@ -73,6 +98,14 @@ class function_type : public type {
 	std::vector<type::Ptr> arg_types;
 
 	virtual void dump(std::ostream &, int) override;
+	virtual block::Ptr clone_impl(void) override {
+		auto np = clone_type(this);
+		np->return_type = clone(return_type);
+		for (auto t: arg_types) {
+			np->arg_types.push_back(clone(t));
+		}
+		return np;
+	}
 };
 class array_type : public type {
 public:
@@ -84,6 +117,12 @@ class array_type : public type {
 	int size;
 
 	virtual void dump(std::ostream &, int) override;
+	virtual block::Ptr clone_impl(void) override {
+		auto np = clone_type(this);
+		np->element_type = clone(element_type);
+		np->size = size;
+		return np;
+	}
 };
 
 // Types for complete closure
@@ -97,6 +136,12 @@ class builder_var_type : public type {
 	type::Ptr closure_type;
 
 	virtual void dump(std::ostream &, int) override;
+	virtual block::Ptr clone_impl(void) override {
+		auto np = clone_type(this);
+		np->builder_var_type_id = builder_var_type_id;
+		np->closure_type = clone(closure_type);
+		return np;
+	}
 };
 
 class named_type : public type {
@@ -109,6 +154,15 @@ class named_type : public type {
 	}
 
 	virtual void dump(std::ostream &, int) override;
+
+	virtual block::Ptr clone_impl(void) override {
+		auto np = clone_type(this);
+		np->type_name = type_name;
+		for (auto t: template_args) {
+			np->template_args.push_back(clone(t));
+		}
+		return np;
+	}
 };
 
 class var : public block {
@@ -137,6 +191,13 @@ class var : public block {
 			return false;
 		return true;
 	}
+	virtual block::Ptr clone_impl(void) override {
+		auto np = clone_obj(this);
+		np->var_name = var_name;
+		np->preferred_name = preferred_name;
+		np->var_type = clone(var_type);
+		return np;
+	}
 };
 
 } // namespace block
diff --git a/src/builder/builder_context.cpp b/src/builder/builder_context.cpp
index 94cc2b9..1736327 100644
--- a/src/builder/builder_context.cpp
+++ b/src/builder/builder_context.cpp
@@ -280,6 +280,10 @@ block::stmt::Ptr builder_context::extract_ast_from_function_impl(void) {
 	std::vector<bool> b;
 
 	block::stmt::Ptr ast = extract_ast_from_function_internal(b);
+
+	// Before making any changes, untangle the whole AST
+	ast = clone(ast);
+
 	block::var_namer::name_vars(ast);
 
 	block::label_collector collector;