llvm/clang-tools-extra/docs/clang-tidy/checks/cppcoreguidelines/pro-type-union-access.rst

.. title:: clang-tidy - cppcoreguidelines-pro-type-union-access

cppcoreguidelines-pro-type-union-access
=======================================

This check flags all access to members of unions. Passing unions as a whole is
not flagged.

Reading from a union member assumes that member was the last one written, and
writing to a union member assumes another member with a nontrivial destructor
had its destructor called. This is fragile because it cannot generally be
enforced to be safe in the language and so relies on programmer discipline to
get it right.

This rule is part of the `Type safety (Type.7)
<https://isocpp.github.io/CppCoreGuidelines/CppCoreGuidelines#Pro-type-unions>`_
profile from the C++ Core Guidelines.