= Allocation Control As <<ref_value_from>> creates a <<ref_value>> object, users may want to control the way memory is allocated for it. For this reason the function has an optional <<ref_storage_ptr>> parameter, that is used to set the {ref_memory_resource} for the result. <<ref_value_to>> does not have a similar parameter, as <<ref_value>> is not created. As the conversion result is set via an output parameter of type `value&`, the intended <<ref_storage_ptr>> is correctly propagated. But users still should take care to not create temporaries using the default {ref_memory_resource} by accident. For example, consider this alternative implementation of `tag_invoke` for `ip_address` from the section <<custom_conversions>>. ``` void tag_invoke( const value_from_tag&, value& jv, ip_address const& addr ) { jv = array{ b[0], b[1], b[2], b[3] }; } ``` This implementation explicitly creates an <<ref_array>> rather than relying on assignment from an initializer list. But the array uses default {ref_memory_resource}, not the one used by `jv`. To avoid creating such temporaries with an incorrect {ref_memory_resource}, using <<ref_value>>\'s member functions <<ref_value_emplace_array>>, <<ref_value_emplace_object>>, and <<ref_value_emplace_string>> can be helpful.