llvm-project

915372a8 - [clang-tidy] In C++17, callee is guaranteed to be sequenced before arguments. (#93623)

[clang-tidy] In C++17, callee is guaranteed to be sequenced before arguments. (#93623) This eliminates false positives in bugprone-use-after-move where a variable is used in the callee and moved from in the arguments. We introduce one special case: If the callee is a MemberExpr with a DeclRefExpr as its base, we consider it to be sequenced after the arguments. This is because the variable referenced in the base will only actually be accessed when the call happens, i.e. once all of the arguments have been evaluated. This has no basis in the C++ standard, but it reflects actual behavior that is relevant to a use-after-move scenario: ```c++ a.bar(consumeA(std::move(a)); ``` In this example, we end up accessing a after it has been moved from, even though nominally the callee a.bar is evaluated before the argument consumeA(std::move(a)). Treating this scenario correctly has required rewriting the logic in bugprone-use-after-move that governs whether the use happens in a later loop iteration than the move. This was previously based on an unsound heuristic (does the use come lexically before the move?); we now use a more rigourous criterion based on reachability in the CFG. Fixes #57758 Fixes #59612 Co-authored-by: martinboehme <mboehme@google.com>