[PATCH] D13784: [clang-tidy] add check cppcoreguidelines-pro-type-union-access

[Matthias Gehre via cfe-commits]

mgehre created this revision.
mgehre added reviewers: alexfh, sbenza, bkramer, aaron.ballman.
mgehre added a subscriber: cfe-commits.

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" profile of the C++ Core
Guidelines, see
https://github.com/isocpp/CppCoreGuidelines/blob/master/CppCoreGuidelines.md#-type7-avoid-accessing-members-of-raw-unions-prefer-variant-instead

http://reviews.llvm.org/D13784

Files:
  clang-tidy/cppcoreguidelines/CMakeLists.txt
  clang-tidy/cppcoreguidelines/CppCoreGuidelinesTidyModule.cpp
  clang-tidy/cppcoreguidelines/ProTypeUnionAccessCheck.cpp
  clang-tidy/cppcoreguidelines/ProTypeUnionAccessCheck.h
  docs/clang-tidy/checks/cppcoreguidelines-pro-type-union-access.rst
  docs/clang-tidy/checks/list.rst
  test/clang-tidy/cppcoreguidelines-pro-type-union-access.cpp

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