NamespaceRegistry uses a bslma::Allocator to supply memory.
NamespaceRegistry
bslma::Allocator
Declared in <balxml_namespaceregistry.h>
<balxml_namespaceregistry.h>
operator BloombergLP::bslmf::NestedTraitDeclaration<NamespaceRegistry, UsesBslmaAllocator>() const;