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major problems. 1) There where static functions and variables that could cause link errors if tclap where used in different files (e.g. file1.cc and file2.cc included tclap then compiling both files would give hard symbols for some variables which would produce multiple definition when linking) 2) The dependencies of tclap was a bit strange (CmdLine depends on Args and Args depends on CmdLine for instance) The first problem I solved by removing all static variables putting them in static member functions (which are weak-symbols). So for instance every where there previously was something like x = _delimiter there now is x = delimiter() or in case of write acces delimiterRef() = x instead of _delimiter = x (I had to append the Ref because there where already functions with the same name as the variables). To solve the problem with static functions I simply inlined them. This causes the compiler to produce a weak symbol or inline if appropriate. We can put the functions inside the class declaration later to make the code look better. This worked fine in all but two cases. In the ValueArg and MultiArg classes I had to do a "hack" to work around the specialization template for extractValue<std::string>. The code for this is very simple but it might look strange an stupid at first but it is only to resolve the specialisation to a weak symbol. What I did was I put the implementations of extractValue in a helper class and I could then create a specialized class instead of function and everything worked out. I think now in retrospect there might be better solutions to this but I'll think a bit more on it (maybe some type of inlining on the specialized version would suffice but I'm not sure). To handle the dependencies I had to do some rewriting. The first step was to introduce a new class CmdLineInterface that is a purely abstract base of CmdLine that specifies the functions needed by Arg and friends. Thus Arg classes now takes an CmdLineInterface object as input instead (however only CmdLine can ever be instantiated of-course). With this extra class cleaning up the dependencies was quite simple, I've attached a dependency graph to the mail (depgraph.png). I also cleaned up the #includes so now only what actually needs inclusion is included. A nice side effect of this is that the impl. of CmdLine is now put back into CmdLine.h (where I guess you wanted it) which (recursivly) includes everything else needed. Just to make things clear for myself regarding the class dependencies I made a class TCLAP::Exception that inherits from std::exception and is a base of ArgException (Exception does nothing currently). If we don't want the Exception class it can be removed, however I think it could be a nice logic to have a base Exception class that every exception inherits from, but we can discuss that when we decide how to handle exceptions.