Subclassing In DLL's with C++
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I am developing an application that needs to read in several file formats and merge the data.  Because we may want to support additional formats in the future, the file readers have to be developed as DLLs, and loaded at runtime based on user input.  I will normally be loading two DLLs at a time.  
I was thinking that I could create an Abstract Interface ([Like this][1]), but if I use a factory function in each of my (subclassed) DLL classes, when I load two DLLs, the two function definitions will interfere with each other.  Am I missing something?  Is there a better way to do this?

Thanks!

  [1]: http://www.codeproject.com/Articles/28969/HowTo-Export-C-classes-from-a-DLL#CppMatureApproach