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gennaroprota merged 1 commit into from
Aug 18, 2026
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Document that polymorphic archives require an nvp #385

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9 changes: 9 additions & 0 deletions doc/archive_reference.html
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Expand Up @@ -411,6 +411,15 @@ <h4>Usage</h4>
serialize such a primitive type will result in a compilation error since the common polymorphic
interface is static and cannot instantiate code for a new type.

<p>
Note also that every value written through a polymorphic archive has to be given a name, with
<code style="white-space: normal">BOOST_SERIALIZATION_NVP</code> or
<code style="white-space: normal">make_nvp</code>. Which archive is on the other end is settled
at run time, and it may turn out to be an XML one, where a value is written as an element and so
must be named. A templated XML archive rejects an unnamed value where it is written; the
polymorphic interface cannot, because at that point the archive type is not yet known, and the
value is written without an element around it. The resulting document cannot be read back.

<p>
The main utility of polymorphic archives will be to permit the building of class DLLs that will
include serialization code for all present and future archives with no redundant code.
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