C++ Coding Standards: 101 Rules, Guidelines, and Best Practices

10. Minimize global and shared data

Summary

Sharing causes contention: Avoid shared data, especially global data. Shared data increases coupling, which reduces maintainability and often performance.

Discussion

This statement is more general than Item 18‘s specific treatment.

Avoid data with external linkage at namespace scope or as static class members. These complicate program logic and cause tighter coupling between different (and, worse, distant) parts of the program. Shared data weakens unit testing because the correctness of a piece of code that uses shared data is conditioned on the history of changes to the data, and further conditions the functioning of acres of yet-unknown code that subsequently uses the data further.

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