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[libc++] LWG3643: Missing constexpr in std::counted_iterator (#87901)

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This pull request implements LWG3643: Missing constexpr in
std::counted_iterator. Specifically, one overload of
std::counted_operator::operator++ was not marked as constexpr,
despite being eligible for it after the introduction of try-block
support in constexpr functions in C++20.
This commit is contained in:
Xiaoyang Liu 2024-04-12 10:04:21 -04:00 committed by GitHub
parent b4df0da9e8
commit 2a5ba4fb89
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GPG Key ID: B5690EEEBB952194
3 changed files with 24 additions and 25 deletions
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2
libcxx/docs/Status/Cxx23Issues.csv
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@ -150,7 +150,7 @@
"`3619 <https://wg21.link/LWG3619>`__","Specification of ``vformat_to`` contains ill-formed ``formatted_size`` calls","February 2022","|Nothing to do|","","|format|"
"`3621 <https://wg21.link/LWG3621>`__","Remove feature-test macro ``__cpp_lib_monadic_optional`` ","February 2022","|Complete|","15.0"
"`3632 <https://wg21.link/LWG3632>`__","``unique_ptr`` ""Mandates: This constructor is not selected by class template argument deduction""","February 2022","|Nothing to do|",""
"`3643 <https://wg21.link/LWG3643>`__","Missing ``constexpr`` in ``std::counted_iterator`` ","February 2022","","","|ranges|"
"`3643 <https://wg21.link/LWG3643>`__","Missing ``constexpr`` in ``std::counted_iterator`` ","February 2022","|Complete|","19.0","|ranges|"
"`3648 <https://wg21.link/LWG3648>`__","``format`` should not print ``bool`` with ``'c'`` ","February 2022","|Complete|","15.0","|format|"
"`3649 <https://wg21.link/LWG3649>`__","[fund.ts.v2] Reinstate and bump ``__cpp_lib_experimental_memory_resource`` feature test macro","February 2022","",""
"`3650 <https://wg21.link/LWG3650>`__","Are ``std::basic_string`` 's ``iterator`` and ``const_iterator`` constexpr iterators?","February 2022","|Nothing to do|",""

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2
libcxx/include/__iterator/counted_iterator.h
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@ -129,7 +129,7 @@ public:
return *this;
}
_LIBCPP_HIDE_FROM_ABI decltype(auto) operator++(int) {
_LIBCPP_HIDE_FROM_ABI constexpr decltype(auto) operator++(int) {
_LIBCPP_ASSERT_UNCATEGORIZED(__count_ > 0, "Iterator already at or past end.");
--__count_;
# ifndef _LIBCPP_HAS_NO_EXCEPTIONS

45
libcxx/test/std/iterators/predef.iterators/counted.iterator/increment.pass.cpp
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@ -9,7 +9,7 @@
// UNSUPPORTED: c++03, c++11, c++14, c++17
// constexpr counted_iterator& operator++();
// decltype(auto) operator++(int);
// constexpr decltype(auto) operator++(int);
// constexpr counted_iterator operator++(int)
// requires forward_iterator<I>;
@ -62,6 +62,26 @@ concept PlusEnabled = requires(Iter& iter) {
constexpr bool test() {
int buffer[8] = {1, 2, 3, 4, 5, 6, 7, 8};
{
using Counted = std::counted_iterator<InputOrOutputArchetype>;
std::counted_iterator iter(InputOrOutputArchetype{buffer}, 8);
iter++;
assert((++iter).base().ptr == buffer + 2);
ASSERT_SAME_TYPE(decltype(iter++), void);
ASSERT_SAME_TYPE(decltype(++iter), Counted&);
}
{
using Counted = std::counted_iterator<cpp20_input_iterator<int*>>;
std::counted_iterator iter(cpp20_input_iterator<int*>{buffer}, 8);
iter++;
assert(++iter == Counted(cpp20_input_iterator<int*>{buffer + 2}, 6));
ASSERT_SAME_TYPE(decltype(iter++), void);
ASSERT_SAME_TYPE(decltype(++iter), Counted&);
}
{
using Counted = std::counted_iterator<forward_iterator<int*>>;
std::counted_iterator iter(forward_iterator<int*>{buffer}, 8);
@ -95,29 +115,8 @@ int main(int, char**) {
test();
static_assert(test());
int buffer[8] = {1, 2, 3, 4, 5, 6, 7, 8};
{
using Counted = std::counted_iterator<InputOrOutputArchetype>;
std::counted_iterator iter(InputOrOutputArchetype{buffer}, 8);
iter++;
assert((++iter).base().ptr == buffer + 2);
ASSERT_SAME_TYPE(decltype(iter++), void);
ASSERT_SAME_TYPE(decltype(++iter), Counted&);
}
{
using Counted = std::counted_iterator<cpp20_input_iterator<int*>>;
std::counted_iterator iter(cpp20_input_iterator<int*>{buffer}, 8);
iter++;
assert(++iter == Counted(cpp20_input_iterator<int*>{buffer + 2}, 6));
ASSERT_SAME_TYPE(decltype(iter++), void);
ASSERT_SAME_TYPE(decltype(++iter), Counted&);
}
#ifndef TEST_HAS_NO_EXCEPTIONS
int buffer[8] = {1, 2, 3, 4, 5, 6, 7, 8};
{
using Counted = std::counted_iterator<ThrowsOnInc<int*>>;
std::counted_iterator iter(ThrowsOnInc<int*>{buffer}, 8);