fix: atomic shared_ptr checks

Author: alandefreitas

include/mrdocs/Dom/Object.hpp

@@ -432,7 +432,11 @@ class MRDOCS_DECL
 class MRDOCS_DECL
     LazyObjectImpl : public ObjectImpl
 {
+#ifdef __cpp_lib_atomic_shared_ptr
     std::atomic<std::shared_ptr<ObjectImpl>> mutable sp_;
+#else
+    std::shared_ptr<ObjectImpl> mutable sp_;
+#endif
 
     using impl_type = Object::impl_type;
 

src/lib/Dom/Object.cpp

@@ -217,6 +217,7 @@ ObjectImpl&
 LazyObjectImpl::
 obj() const
 {
+#ifdef __cpp_lib_atomic_shared_ptr
     auto impl = sp_.load();
     if(impl)
         return *impl;
@@ -225,6 +226,9 @@ obj() const
             expected, construct().impl()))
         return *sp_.load();
     return *expected;
+#else
+    return *sp_;
+#endif
 }
 
 std::size_t