[all-commits] [llvm/llvm-project] 068fe2: [Clang] Rebuild lambda captures in default member ...

[Yuxuan Chen via All-commits]

  Branch: refs/heads/users/yuxuanchen1997/fix-cwg1815-lambda-capture-cleanup
  Home:   https://github.com/llvm/llvm-project
  Commit: 068fe29bf343002213af297972167c641c50df28
      https://github.com/llvm/llvm-project/commit/068fe29bf343002213af297972167c641c50df28
  Author: Yuxuan Chen <ych at meta.com>
  Date:   2026-06-24 (Wed, 24 Jun 2026)

  Changed paths:
    M clang/lib/Sema/SemaExpr.cpp
    A clang/test/CodeGenCXX/gh196469-default-member-init-lambda-cleanup.cpp
    A clang/test/SemaCXX/gh196469-default-member-init-lambda-capture.cpp

  Log Message:
  -----------
  [Clang] Rebuild lambda captures in default member initializers

Fixes https://github.com/llvm/llvm-project/issues/196469

Since the CWG1815 implementation, `InitListChecker` rebuilds a default
member initializer at its point of use in aggregate initialization. The
rebuild uses the `EnsureImmediateInvocationInDefaultArgs` tree
transform, where `TransformCXXBindTemporaryExpr` strips
`CXXBindTemporaryExpr` nodes, relying on the subexpression's rebuild to
re-create the temporary binding: every `Rebuild*` path funnels through
`Sema::MaybeBindToTemporary`, which also re-registers the cleanup in
the current evaluation context.

However, the transform overrides `TransformLambdaExpr` to return the
closure unchanged because the lambda body is not a subexpression. That
skips the `MaybeBindToTemporary` call that `BuildLambdaExpr` ends with.
The rebuilt initializer then lacks both the `CXXBindTemporaryExpr`
around the closure and the `ExprWithCleanups` marker, so CodeGen never
emits the closure's destructor and init-captured members leak.

Lambda init-captures are different from the body: their initializers are
evaluated in the enclosing context and can also contain immediate
invocations that need to be rebuilt at the default-initializer use site.
Visit init-captures when deciding whether the default initializer needs
rebuilding, and rebuild the lambda shell/captures while using
`SkipLambdaBody` to leave the body itself untouched. Rebuilding the
lambda this way also restores the closure temporary binding and cleanup
through `BuildLambdaExpr`.

Co-Authored-By: GPT-5.5 <noreply at openai.com>



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