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Document that the definition file needs the archive headers #376

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Merged
gennaroprota merged 1 commit into from
Aug 13, 2026
Merged

Document that the definition file needs the archive headers #376

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11 changes: 11 additions & 0 deletions doc/special.html
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Original file line number Diff line number Diff line change
Expand Up @@ -444,6 +444,17 @@ <h3><a name="export">Exporting Class Serialization</a></h3>
<code style="white-space: normal">BOOST_CLASS_EXPORT_IMPLEMENT</code>
in the class definition file.

<p>
This makes the rule easy to follow but does not remove it. The definition
file has to include the archive class headers itself, before
<code style="white-space: normal">BOOST_CLASS_EXPORT_IMPLEMENT</code>
is invoked, just as it would for
<code style="white-space: normal">BOOST_CLASS_EXPORT</code>.
A definition file which includes none of them instantiates no serialization
code at all, and serializing a pointer to such a class then throws
<code style="white-space: normal">unregistered_class</code>
when the program is run.

<p>
This system has certain implications for placing code in static or shared
libraries. Placing <code style="white-space: normal">BOOST_CLASS_EXPORT</code>
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7 changes: 5 additions & 2 deletions doc/traits.html
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Expand Up @@ -247,8 +247,11 @@ <h3><a name="export">Export Key</a></h3>
This is addressed by invoking
<code style="white-space: normal">BOOST_CLASS_EXPORT_IMPLEMENT(T)</code>
in the file which defines (implements) the class T.
This ensures that code for the derived class T will
be explicitly instantiated.
That instantiates the code for the archive classes whose headers the file
includes, so the file has to include them before the macro is invoked.
See
<a href="special.html#export">Exporting Class Serialization</a>
for the details, and for what happens when it includes none of them.
<li> There needs to be some sort of identifier which can
be used to select the code to be invoked when the object
is loaded.
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