[Doxygen] EXTRACT_ALL and warnings

Hello,

in our company we are developing in C (without ++ ;)).
The source code is documented to the best of the knowledge. But some developers are not as motivated as others. So some things remain undocumented or are documented wrong.

In the configuration (Doxyfile) we use EXTRACT_ALL = YES to ... well ... extract all to the html-output.
But Doxygen is not showing any warning when using this option. Even if the following options are set:
WARNINGS = YES
WARN_IF_UNDOCUMENTED = YES
WARN_IF_DOC_ERROR = YES
WARN_NO_PARAMDOC = YES

Is it possible to extract all and to get the warnings?