libc++-9-dev - 1:9.0.1-16.1 main

libc++ is another implementation of the C++ standard library
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Features and Goals
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* Correctness as defined by the C++ standards.
* Fast execution.
* Minimal memory use.
* Fast compile times.
* ABI compatibility with gcc's libstdc++ for some low-level features such
as exception objects, rtti and memory allocation.
* Extensive unit tests.