Implement the second part of P1227R2 - Signed ssize() functions. Reviewed as https://reviews.llvm.org/D58642
git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@354950 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/include/iterator b/include/iterator
index ce0be3d..bce6e90 100644
--- a/include/iterator
+++ b/include/iterator
@@ -399,6 +399,11 @@
// 24.8, container access:
template <class C> constexpr auto size(const C& c) -> decltype(c.size()); // C++17
template <class T, size_t N> constexpr size_t size(const T (&array)[N]) noexcept; // C++17
+
+template <class C> constexpr auto ssize(const C& c)
+ -> common_type_t<ptrdiff_t, make_signed_t<decltype(c.size())>>; // C++20
+template <class T, ptrdiff_t> constexpr ptrdiff_t ssize(const T (&array)[N]) noexcept; // C++20
+
template <class C> constexpr auto empty(const C& c) -> decltype(c.empty()); // C++17
template <class T, size_t N> constexpr bool empty(const T (&array)[N]) noexcept; // C++17
template <class E> constexpr bool empty(initializer_list<E> il) noexcept; // C++17
@@ -1858,6 +1863,19 @@
inline _LIBCPP_INLINE_VISIBILITY
constexpr size_t size(const _Tp (&)[_Sz]) noexcept { return _Sz; }
+#if _LIBCPP_STD_VER > 17
+template <class _Cont>
+inline _LIBCPP_INLINE_VISIBILITY
+constexpr auto ssize(const _Cont& __c)
+_NOEXCEPT_(noexcept(static_cast<common_type_t<ptrdiff_t, make_signed_t<decltype(__c.size())>>>(__c.size())))
+-> common_type_t<ptrdiff_t, make_signed_t<decltype(__c.size())>>
+{ return static_cast<common_type_t<ptrdiff_t, make_signed_t<decltype(__c.size())>>>(__c.size()); }
+
+template <class _Tp, ptrdiff_t _Sz>
+inline _LIBCPP_INLINE_VISIBILITY
+constexpr ptrdiff_t ssize(const _Tp (&)[_Sz]) noexcept { return _Sz; }
+#endif
+
template <class _Cont>
_LIBCPP_NODISCARD_AFTER_CXX17 inline _LIBCPP_INLINE_VISIBILITY
constexpr auto empty(const _Cont& __c)
diff --git a/test/std/iterators/iterator.container/size.pass.cpp b/test/std/iterators/iterator.container/size.pass.cpp
index db215b8..ec43c1e 100644
--- a/test/std/iterators/iterator.container/size.pass.cpp
+++ b/test/std/iterators/iterator.container/size.pass.cpp
@@ -27,6 +27,13 @@
template<typename C>
+void test_container( C& c)
+{
+// Can't say noexcept here because the container might not be
+ assert ( std::size(c) == c.size());
+}
+
+template<typename C>
void test_const_container( const C& c )
{
// Can't say noexcept here because the container might not be
@@ -36,23 +43,14 @@
template<typename T>
void test_const_container( const std::initializer_list<T>& c)
{
-// ASSERT_NOEXCEPT(std::size(c));
-// For some reason, there isn't a std::size() for initializer lists
- assert ( std::size(c) == c.size());
-}
-
-template<typename C>
-void test_container( C& c)
-{
-// Can't say noexcept here because the container might not be
+ LIBCPP_ASSERT_NOEXCEPT(std::size(c)); // our std::size is conditionally noexcept
assert ( std::size(c) == c.size());
}
template<typename T>
void test_container( std::initializer_list<T>& c )
{
-// ASSERT_NOEXCEPT(std::size(c));
-// For some reason, there isn't a std::size() for initializer lists
+ LIBCPP_ASSERT_NOEXCEPT(std::size(c)); // our std::size is conditionally noexcept
assert ( std::size(c) == c.size());
}
diff --git a/test/std/iterators/iterator.container/ssize.pass.cpp b/test/std/iterators/iterator.container/ssize.pass.cpp
new file mode 100644
index 0000000..c34614d
--- /dev/null
+++ b/test/std/iterators/iterator.container/ssize.pass.cpp
@@ -0,0 +1,120 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++98, c++03, c++11, c++14, c++17
+
+// <iterator>
+// template <class C> constexpr auto ssize(const C& c)
+// -> common_type_t<ptrdiff_t, make_signed_t<decltype(c.size())>>; // C++20
+// template <class T, ptrdiff_t> constexpr ptrdiff_t ssize(const T (&array)[N]) noexcept; // C++20
+
+#include <iterator>
+#include <cassert>
+#include <vector>
+#include <array>
+#include <list>
+#include <initializer_list>
+#include <string_view>
+
+#include "test_macros.h"
+
+
+struct short_container {
+ uint16_t size() const { return 60000; } // not noexcept
+ };
+
+
+
+template<typename C>
+void test_container(C& c)
+{
+// Can't say noexcept here because the container might not be
+ static_assert( std::is_signed_v<decltype(std::ssize(c))>, "");
+ assert ( std::ssize(c) == static_cast<decltype(std::ssize(c))>(c.size()));
+}
+
+template<typename C>
+void test_const_container(const C& c)
+{
+// Can't say noexcept here because the container might not be
+ static_assert( std::is_signed_v<decltype(std::ssize(c))>, "");
+ assert ( std::ssize(c) == static_cast<decltype(std::ssize(c))>(c.size()));
+}
+
+template<typename T>
+void test_const_container(const std::initializer_list<T>& c)
+{
+ LIBCPP_ASSERT_NOEXCEPT(std::ssize(c)); // our std::ssize is conditionally noexcept
+ static_assert( std::is_signed_v<decltype(std::ssize(c))>, "");
+ assert ( std::ssize(c) == static_cast<decltype(std::ssize(c))>(c.size()));
+}
+
+template<typename T>
+void test_container(std::initializer_list<T>& c)
+{
+ LIBCPP_ASSERT_NOEXCEPT(std::ssize(c)); // our std::ssize is conditionally noexcept
+ static_assert( std::is_signed_v<decltype(std::ssize(c))>, "");
+ assert ( std::ssize(c) == static_cast<decltype(std::ssize(c))>(c.size()));
+}
+
+template<typename T, size_t Sz>
+void test_const_array(const T (&array)[Sz])
+{
+ ASSERT_NOEXCEPT(std::ssize(array));
+ static_assert( std::is_signed_v<decltype(std::ssize(array))>, "");
+ assert ( std::ssize(array) == Sz );
+}
+
+int main(int, char**)
+{
+ std::vector<int> v; v.push_back(1);
+ std::list<int> l; l.push_back(2);
+ std::array<int, 1> a; a[0] = 3;
+ std::initializer_list<int> il = { 4 };
+ test_container ( v );
+ ASSERT_SAME_TYPE(ptrdiff_t, decltype(std::ssize(v)));
+ test_container ( l );
+ ASSERT_SAME_TYPE(ptrdiff_t, decltype(std::ssize(l)));
+ test_container ( a );
+ ASSERT_SAME_TYPE(ptrdiff_t, decltype(std::ssize(a)));
+ test_container ( il );
+ ASSERT_SAME_TYPE(ptrdiff_t, decltype(std::ssize(il)));
+
+ test_const_container ( v );
+ test_const_container ( l );
+ test_const_container ( a );
+ test_const_container ( il );
+
+ std::string_view sv{"ABC"};
+ test_container ( sv );
+ ASSERT_SAME_TYPE(ptrdiff_t, decltype(std::ssize(sv)));
+ test_const_container ( sv );
+
+ static constexpr int arrA [] { 1, 2, 3 };
+ ASSERT_SAME_TYPE(ptrdiff_t, decltype(std::ssize(arrA)));
+ static_assert( std::is_signed_v<decltype(std::ssize(arrA))>, "");
+ test_const_array ( arrA );
+
+// From P1227R2:
+// Note that the code does not just return the std::make_signed variant of
+// the container's size() method, because it's conceivable that a container
+// might choose to represent its size as a uint16_t, supporting up to
+// 65,535 elements, and it would be a disaster for std::ssize() to turn a
+// size of 60,000 into a size of -5,536.
+
+ short_container sc;
+// is the return type signed? Is it big enough to hold 60K?
+// is the "signed version" of sc.size() too small?
+ static_assert( std::is_signed_v< decltype(std::ssize(sc))>, "");
+ static_assert( std::numeric_limits< decltype(std::ssize(sc))>::max() > 60000, "");
+ static_assert( std::numeric_limits<std::make_signed_t<decltype(std:: size(sc))>>::max() < 60000, "");
+ assert (std::ssize(sc) == 60000);
+ LIBCPP_ASSERT_NOT_NOEXCEPT(std::ssize(sc));
+
+ return 0;
+}
