* [committed] libstdc++: Fix std::array<T, 0>::data() to be a constant expression [PR108258]
@ 2023-01-04 11:54 Jonathan Wakely
0 siblings, 0 replies; only message in thread
From: Jonathan Wakely @ 2023-01-04 11:54 UTC (permalink / raw)
To: libstdc++, gcc-patches
Tested x86_64-linux. Pushed to trunk.
-- >8 --
When I refactored the __array_traits helper I broke this.
libstdc++-v3/ChangeLog:
PR libstdc++/108258
* include/std/array (__array_traits<T, 0>::operator T*()): Add
constexpr.
* testsuite/23_containers/array/element_access/constexpr_c++17.cc: Check
std::array<T, 0>::data().
---
libstdc++-v3/include/std/array | 2 +-
.../array/element_access/constexpr_c++17.cc | 19 ++++++++++++++++---
2 files changed, 17 insertions(+), 4 deletions(-)
diff --git a/libstdc++-v3/include/std/array b/libstdc++-v3/include/std/array
index e26390e6f80..c50a201b032 100644
--- a/libstdc++-v3/include/std/array
+++ b/libstdc++-v3/include/std/array
@@ -69,7 +69,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
// Conversion to a pointer produces a null pointer.
__attribute__((__always_inline__))
- operator _Tp*() const noexcept { return nullptr; }
+ constexpr operator _Tp*() const noexcept { return nullptr; }
};
using _Is_swappable = true_type;
diff --git a/libstdc++-v3/testsuite/23_containers/array/element_access/constexpr_c++17.cc b/libstdc++-v3/testsuite/23_containers/array/element_access/constexpr_c++17.cc
index b6878fd0c59..b92aa5c04e2 100644
--- a/libstdc++-v3/testsuite/23_containers/array/element_access/constexpr_c++17.cc
+++ b/libstdc++-v3/testsuite/23_containers/array/element_access/constexpr_c++17.cc
@@ -34,21 +34,34 @@ constexpr std::size_t test01()
auto v2 = a.at(2);
auto v3 = a.front();
auto v4 = a.back();
- return v1 + v2 + v3 + v4;
+ auto v5 = *a.data();
+ return v1 + v2 + v3 + v4 + v5;
}
static_assert( test01() == (55 + 66 + 0 + 2) );
constexpr std::size_t test02()
{
- // array
+ // const array
typedef std::array<std::size_t, 6> array_type;
const array_type a = { { 0, 55, 66, 99, 4115, 2 } };
auto v1 = a[1];
auto v2 = a.at(2);
auto v3 = a.front();
auto v4 = a.back();
- return v1 + v2 + v3 + v4;
+ auto v5 = *a.data();
+ return v1 + v2 + v3 + v4 + v5;
}
static_assert( test02() == (55 + 66 + 0 + 2) );
+
+constexpr bool test_zero()
+{
+ // zero-sized array (PR libstdc++/108258)
+ std::array<int, 0> a{};
+ auto v4 = a.data();
+ // The standard says this is unspecified, it's null for our implementation:
+ return a.data() == nullptr;
+}
+
+static_assert( test_zero() );
--
2.39.0
^ permalink raw reply [flat|nested] only message in thread
only message in thread, other threads:[~2023-01-04 11:54 UTC | newest]
Thread overview: (only message) (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2023-01-04 11:54 [committed] libstdc++: Fix std::array<T, 0>::data() to be a constant expression [PR108258] Jonathan Wakely
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).