[PATCH] D78767: [Sema] Teach -Wcast-align to compute a more accurate alignment when the source expression has array subscript or pointer arithmetic operators

[Akira Hatanaka via Phabricator via cfe-commits]

ahatanak updated this revision to Diff 263238.
ahatanak marked an inline comment as done.
ahatanak added a comment.

Define two helper functions in Sema that compute the alignment of a VarDecl and a constant offset from it and use them instead of the classes for evaluating lvalue and pointer expressions in ExprConstant.cpp.

Using the classes in ExprConstant.cpp to compute an expression alignment as I did in the previous patch is probably not a good idea since they are for evaluating constant expressions. They don't return the lvalue base variables and offsets in some cases ( for example, `(A *)&m_ref` in the test case) and using them for this purpose can make it harder to make changes to the way constant expressions are evaluated. The current patch is far from perfect as it misses many cases that could be detected by the classes in ExprConstant.cpp, but is at least an improvement over what we have now.

I was also thinking about fixing the alignment computation of captured variables, but I think I should do that separately in a follow-up as it might not be trivial. It will probably require looking up the captured variables in all the enclosing `CapturingScopeInfo`s.


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D78767/new/

https://reviews.llvm.org/D78767

Files:
  clang/lib/Sema/SemaChecking.cpp
  clang/test/SemaCXX/warn-cast-align.cpp

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