Use empty_c_void_p for nullptr constant

Author: Smit-create

src/lpython/semantics/python_ast_to_asr.cpp

@@ -5766,6 +5766,8 @@ class BodyVisitor : public CommonVisitor<BodyVisitor> {
                                 x.base.base.loc);
             }
             tmp = ASR::make_ListCompare_t(al, x.base.base.loc, left, asr_op, right, type, value);
+        } else if (ASR::is_a<ASR::CPtr_t>(*dest_type)) {
+            tmp = ASR::make_CPtrCompare_t(al, x.base.base.loc, left, asr_op, right, type, value);
         } else {
             throw SemanticError("Compare not supported for type: " + ASRUtils::type_to_str_python(dest_type),
                                 x.base.base.loc);
@@ -6804,7 +6806,8 @@ class BodyVisitor : public CommonVisitor<BodyVisitor> {
             } else if (call_name == "empty_c_void_p") {
                 // TODO: check that `empty_c_void_p uses` has arguments that are compatible
                 // with the type
-                tmp = nullptr;
+                ASR::ttype_t* type = ASRUtils::TYPE(ASR::make_CPtr_t(al, x.base.base.loc));
+                tmp = ASR::make_PointerNullConstant_t(al, x.base.base.loc, type);
                 return;
             } else if (call_name == "TypeVar") {
                 // Ignore TypeVar for now, we handle it based on the identifier itself