flag and Doc++ is not in your PATH variable, then it is not
possible to generate printable documentation.
</p>
+
+ <li>
+ <p>
+ <code>--enable-compat-blocker=...</code>: the library offers
+ various functions that maintain compatibility with older
+ versions of <acronym>deal.II</acronym>, for example many
+ functions that assume that the mapping between unit and real
+ cell is a (bi-, tri-)linear one. There are respective functions
+ that take a mapping object, and the compatibility functions
+ simply call these with a Q1 mapping object.
+ </p>
+
+ <p>
+ When converting old programs, and also sometimes with new
+ programs, you may want to make sure that these compatibility
+ functions are not called, to ensure that the mapping taken is
+ always the same. In that case, you can configure the library
+ with the flag
+ <code>--enable-compat-blocker=mapping</code>. After
+ recompilation of the library, each access to these functions is
+ blocked, and an exception is thrown.
+ </p>
+
+ <p>
+ In later versions of the library, other compatibility blockers
+ will be implemented as well, as we extend the functionality of
+ the library.
+ </p>
</ul>
<p>