How can I find out the decorated name that will be asigned to each method name ? I'm trying to find out what the decorated name is , so that I may export it , in a DLL .
Forget .DEF files. They are a thing of the past.
Export your functions, be them C functions or C++ symbols, through __declspec(dllimport/dllexport).
If you really need undecorated names, use as suggested by Greg Hewgill, the __declspec(dllimport/dllexport) keywords, combined with extern "C", which will strip those symbols of their decoration...
There are some valid reasons for that: You want to export code that will be used by C code, or you want to use your DLL from modules compiled with different compilers.
And for the second reason, I would instead produce one DLL per compiler, and keep the decorations.
Aside those reasons, why do you want the decorations removed?
Quite the contrary.
If you are working with one compiler (and I suppose you do, because your want to use the decorated names, not extern "C" ones), then keep the C++ decoration/name mangling.
In this way, you'll be able to use full C++ power, that is, namespaces, classes, function/method overloads, etc..
Still, playing manually with symbol decorations is a recipe for disaster: Use dllexport to export your symbols without having to deal with yet another (.DEF) file.