What open source projects in C++ have the highest code quality?

My understanding of the characteristics of quality code are the conventional ones.

* operations on an object that are allowed in a particular object state do not put the object into an invalid state.
* it's prioritized to organize the implementation of each object into the smallest possible number of sub-objects.
* no cryptically abbreviated names are used, except possible in very small scopes.

With the program(s)/executable(s) themselves, as well as modules with corresponding namespaces, being considered singleton objects.

Fair dinkum if you want to name projects that score well under a different understanding of code quality.

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