[libcxx-commits] [libcxx] [libc++] Fix non-conforming member typedef const_reference (PR #121620)

Peng Liu via libcxx-commits libcxx-commits at lists.llvm.org
Fri Jan 3 19:24:31 PST 2025


https://github.com/winner245 created https://github.com/llvm/llvm-project/pull/121620

According to [template.bitset.general], `std::bitset` is only supposed to have one public member typedef, `reference`. The other member typedefs currently defined in `std::bitset`, including `size_type`, `difference_type`, and `const_reference`, are non-conforming and cause ambiguity in name lookup, as demonstrated in issue #121618.

Fixing the non-conforming name `const_reference` is straightforward: we can simplify by replace it with an __uglified name `__const_reference`. However, fixing the names `size_type` and `difference_type` is not so obvious as these names are required by the `__bit_iterator` class and the corresponding algorithms optimized for `__bit_iterators` (e.g., `ranges::fill`).
 

This PR fixes the non-conforming typedef `const_reference` as raised in issue #121618. Further work will be undertaken to address `size_type` and `difference_type`. 



>From e4f1d209be307353d4937e3e83dae5b3f56f2ee4 Mon Sep 17 00:00:00 2001
From: Peng Liu <winner245 at hotmail.com>
Date: Fri, 3 Jan 2025 22:08:08 -0500
Subject: [PATCH] Fix non-conforming member typedef const_reference

---
 libcxx/include/bitset                         | 22 +++++++++----------
 .../bitset.members/index_const.pass.cpp       | 22 +++++++++----------
 .../nonstdmem.uglified.compile.pass.cpp       | 11 ++++++++++
 3 files changed, 33 insertions(+), 22 deletions(-)

diff --git a/libcxx/include/bitset b/libcxx/include/bitset
index 919d2a0f07e096..c16635dc8092cd 100644
--- a/libcxx/include/bitset
+++ b/libcxx/include/bitset
@@ -189,7 +189,7 @@ protected:
   __storage_type __first_[_N_words];
 
   typedef __bit_reference<__bitset> reference;
-  typedef __bit_const_reference<__bitset> const_reference;
+  typedef __bit_const_reference<__bitset> __const_reference;
   typedef __bit_iterator<__bitset, false> __iterator;
   typedef __bit_iterator<__bitset, true> __const_iterator;
 
@@ -199,8 +199,8 @@ protected:
   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX23 reference __make_ref(size_t __pos) _NOEXCEPT {
     return reference(__first_ + __pos / __bits_per_word, __storage_type(1) << __pos % __bits_per_word);
   }
-  _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR const_reference __make_ref(size_t __pos) const _NOEXCEPT {
-    return const_reference(__first_ + __pos / __bits_per_word, __storage_type(1) << __pos % __bits_per_word);
+  _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR __const_reference __make_ref(size_t __pos) const _NOEXCEPT {
+    return __const_reference(__first_ + __pos / __bits_per_word, __storage_type(1) << __pos % __bits_per_word);
   }
   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX23 __iterator __make_iter(size_t __pos) _NOEXCEPT {
     return __iterator(__first_ + __pos / __bits_per_word, __pos % __bits_per_word);
@@ -451,7 +451,7 @@ protected:
   __storage_type __first_;
 
   typedef __bit_reference<__bitset> reference;
-  typedef __bit_const_reference<__bitset> const_reference;
+  typedef __bit_const_reference<__bitset> __const_reference;
   typedef __bit_iterator<__bitset, false> __iterator;
   typedef __bit_iterator<__bitset, true> __const_iterator;
 
@@ -461,8 +461,8 @@ protected:
   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX23 reference __make_ref(size_t __pos) _NOEXCEPT {
     return reference(&__first_, __storage_type(1) << __pos);
   }
-  _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR const_reference __make_ref(size_t __pos) const _NOEXCEPT {
-    return const_reference(&__first_, __storage_type(1) << __pos);
+  _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR __const_reference __make_ref(size_t __pos) const _NOEXCEPT {
+    return __const_reference(&__first_, __storage_type(1) << __pos);
   }
   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX23 __iterator __make_iter(size_t __pos) _NOEXCEPT {
     return __iterator(&__first_ + __pos / __bits_per_word, __pos % __bits_per_word);
@@ -566,7 +566,7 @@ protected:
   friend struct __bit_array<__bitset>;
 
   typedef __bit_reference<__bitset> reference;
-  typedef __bit_const_reference<__bitset> const_reference;
+  typedef __bit_const_reference<__bitset> __const_reference;
   typedef __bit_iterator<__bitset, false> __iterator;
   typedef __bit_iterator<__bitset, true> __const_iterator;
 
@@ -576,8 +576,8 @@ protected:
   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX23 reference __make_ref(size_t) _NOEXCEPT {
     return reference(nullptr, 1);
   }
-  _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR const_reference __make_ref(size_t) const _NOEXCEPT {
-    return const_reference(nullptr, 1);
+  _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR __const_reference __make_ref(size_t) const _NOEXCEPT {
+    return __const_reference(nullptr, 1);
   }
   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX23 __iterator __make_iter(size_t) _NOEXCEPT {
     return __iterator(nullptr, 0);
@@ -619,7 +619,7 @@ public:
 
 public:
   typedef typename __base::reference reference;
-  typedef typename __base::const_reference const_reference;
+  typedef typename __base::__const_reference __const_reference;
 
   // 23.3.5.1 constructors:
   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR bitset() _NOEXCEPT {}
@@ -689,7 +689,7 @@ public:
     return __base::__make_ref(__p);
   }
 #  else
-  _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR const_reference operator[](size_t __p) const {
+  _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR __const_reference operator[](size_t __p) const {
     _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(__p < _Size, "bitset::operator[] index out of bounds");
     return __base::__make_ref(__p);
   }
diff --git a/libcxx/test/std/utilities/template.bitset/bitset.members/index_const.pass.cpp b/libcxx/test/std/utilities/template.bitset/bitset.members/index_const.pass.cpp
index 77eb9056bc6d99..d1bf5b2c5d9926 100644
--- a/libcxx/test/std/utilities/template.bitset/bitset.members/index_const.pass.cpp
+++ b/libcxx/test/std/utilities/template.bitset/bitset.members/index_const.pass.cpp
@@ -18,17 +18,17 @@
 
 template <std::size_t N>
 TEST_CONSTEXPR_CXX23 void test_index_const() {
-    std::vector<std::bitset<N> > const cases = get_test_cases<N>();
-    for (std::size_t c = 0; c != cases.size(); ++c) {
-        std::bitset<N> const v = cases[c];
-        if (v.size() > 0) {
-            assert(v[N/2] == v.test(N/2));
-        }
+  std::vector<std::bitset<N> > const cases = get_test_cases<N>();
+  for (std::size_t c = 0; c != cases.size(); ++c) {
+    std::bitset<N> const v = cases[c];
+    if (v.size() > 0) {
+      assert(v[N / 2] == v.test(N / 2));
     }
+  }
 #if !defined(_LIBCPP_VERSION) || defined(_LIBCPP_ABI_BITSET_VECTOR_BOOL_CONST_SUBSCRIPT_RETURN_BOOL)
-    ASSERT_SAME_TYPE(decltype(cases[0][0]), bool);
+  ASSERT_SAME_TYPE(decltype(cases[0][0]), bool);
 #else
-    ASSERT_SAME_TYPE(decltype(cases[0][0]), typename std::bitset<N>::const_reference);
+  ASSERT_SAME_TYPE(decltype(cases[0][0]), typename std::bitset<N>::__const_reference);
 #endif
 }
 
@@ -43,10 +43,10 @@ TEST_CONSTEXPR_CXX23 bool test() {
   test_index_const<65>();
 
   std::bitset<1> set_;
-  set_[0] = false;
+  set_[0]         = false;
   const auto& set = set_;
-  auto b = set[0];
-  set_[0] = true;
+  auto b          = set[0];
+  set_[0]         = true;
 #if !defined(_LIBCPP_VERSION) || defined(_LIBCPP_ABI_BITSET_VECTOR_BOOL_CONST_SUBSCRIPT_RETURN_BOOL)
   assert(!b);
 #else
diff --git a/libcxx/test/std/utilities/template.bitset/bitset.members/nonstdmem.uglified.compile.pass.cpp b/libcxx/test/std/utilities/template.bitset/bitset.members/nonstdmem.uglified.compile.pass.cpp
index ae3ac819b1f9c6..e5974519ac9355 100644
--- a/libcxx/test/std/utilities/template.bitset/bitset.members/nonstdmem.uglified.compile.pass.cpp
+++ b/libcxx/test/std/utilities/template.bitset/bitset.members/nonstdmem.uglified.compile.pass.cpp
@@ -23,6 +23,7 @@ struct my_base {
   typedef int* iterator;
   typedef const int* const_iterator;
   typedef my_base base;
+  typedef const int& const_reference;
 };
 
 template <std::size_t N>
@@ -57,3 +58,13 @@ static_assert(std::is_same<my_derived<32>::base, my_base>::value, "");
 static_assert(std::is_same<my_derived<48>::base, my_base>::value, "");
 static_assert(std::is_same<my_derived<64>::base, my_base>::value, "");
 static_assert(std::is_same<my_derived<96>::base, my_base>::value, "");
+
+static_assert(std::is_same<my_derived<0>::const_reference, const int&>::value, "");
+static_assert(std::is_same<my_derived<1>::const_reference, const int&>::value, "");
+static_assert(std::is_same<my_derived<8>::const_reference, const int&>::value, "");
+static_assert(std::is_same<my_derived<12>::const_reference, const int&>::value, "");
+static_assert(std::is_same<my_derived<16>::const_reference, const int&>::value, "");
+static_assert(std::is_same<my_derived<32>::const_reference, const int&>::value, "");
+static_assert(std::is_same<my_derived<48>::const_reference, const int&>::value, "");
+static_assert(std::is_same<my_derived<64>::const_reference, const int&>::value, "");
+static_assert(std::is_same<my_derived<96>::const_reference, const int&>::value, "");



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