Hi list, here is a first version of the Max-PD C++ compatibility layer for PD and Max externals. It is GEM style, hence a lot of code is borrowed from this package, but many things have been added to fit for Max/MSP. There are still unsufficiencies, but it should be possible to write standard message and dsp handling externals with very few preprocessor defines separating PD and Max code. Find an overview in the package file readme.txt.
http://www.parasitaere-kapazitaeten.net/Pd/ext/maxpd-0.1.zip
As an example how the above max-pd package is used, take a look at the source of the strictly C++ written xsample objects (at the moment built only for Windows). These externals (xgroove~,xplay~,xrecord~) are flexible and fast objects for doing sample stuff with buffers/arrays (based on the functionality of the respective Max/MSP objects). Some simplistic help patches are included but much more features are yet not well documented.
http://www.parasitaere-kapazitaeten.net/Pd/ext/xsample-0.2.zip
have fun, Thomas