What are some techniques for limiting compilation dependencies in C++ projects?

Question

In a C++ project, compilation dependencies can make a software project difficult to maintain. What are some of the best practices for limiting dependencies, both within a module and across modules?

Answer 1

• Forward Declarations
• Abstract Interfaces
• The Pimpl Idiom

Answer 2

Herb Sutter has a great treatment of this exact topic in Items 26, 27 and 28, "Minimizing Compile-time Dependencies, Parts 1, 2 and 3", in his excellent book Exceptional C++, ISBN: 0201615622.

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IMHO, this is one of the best C++ programming books available.