[libc++] Remove abandoned __append declaration in vector<bool>

[winner245]

The vector<bool> implementation in libcxx contains a declaration of a private __append function, which is neither defined nor used anywhere in the codebase. This PR aims to remove this abandoned declaration, as its presence is misleading and could lead to confusion during future maintenance.

I have no idea why we have a declaration without a definition. My guess is that the declaration might be inherited from the implementation of vector<T>, where __append is both necessary and properly defined. The declaration may have been inadvertently copied from vector<T> to vector<bool> and subsequently abandoned, as vector<bool> never needs it.

[llvmbot]

@llvm/pr-subscribers-libcxx

Author: Peng Liu (winner245)

Changes

The vector<bool> implementation in libcxx contains a declaration of a private __append function, which is neither defined nor used anywhere in the codebase. This PR aims to remove this abandoned declaration, as its presence is misleading and could lead to confusion during future maintenance.

I have no idea why we have a declaration without a definition. My guess is that the declaration might be inherited from the implementation of vector<T>, where __append is both necessary and properly defined. The declaration may have been inadvertently copied from vector<T> to vector<bool> and subsequently abandoned, as vector<bool> never needs it.

---

Full diff: https://github.com/llvm/llvm-project/pull/121673.diff

1 Files Affected:

• (modified) libcxx/include/__vector/vector_bool.h (-1)

diff --git a/libcxx/include/__vector/vector_bool.h b/libcxx/include/__vector/vector_bool.h
index 525fc35b26cc9e..8658745b8a8f9e 100644
--- a/libcxx/include/__vector/vector_bool.h
+++ b/libcxx/include/__vector/vector_bool.h
@@ -442,7 +442,6 @@ class _LIBCPP_TEMPLATE_VIS vector<bool, _Allocator> {
   template <class _InputIterator, class _Sentinel>
   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 void
   __construct_at_end(_InputIterator __first, _Sentinel __last, size_type __n);
-  _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 void __append(size_type __n, const_reference __x);
   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 reference __make_ref(size_type __pos) _NOEXCEPT {
     return reference(__begin_ + __pos / __bits_per_word, __storage_type(1) << __pos % __bits_per_word);
   }

[philnik777]

Looks like it's been there since the initial import and was never defined.