Tested x86_64-linux. Pushed to trunk. Backport needed for gcc-13 too.
-- >8 --
For 32-bit targets using -pedantic (or using Clang) makes the expression
_M_elems[0] ambiguous. The overloaded operator[] that we want to call
has a size_t parameter, but 0 is type ptrdiff_t for many ILP32 targets,
so using the implicit conversion from _M_elems to T* and then
subscripting that is also viable.
Change the 0 to (size_type)0 and also make the conversion to T*
explicit, so that's it's not viable here. The latter change requires a
static_cast in data() where we really do want to convert _M_elems to a
pointer.
libstdc++-v3/ChangeLog:
PR libstdc++/110139
* include/std/array (__array_traits<T, 0>::operator T*()): Make
conversion operator explicit.
(array::front): Use size_type as subscript operand.
(array::data): Use static_cast to make conversion explicit.
* testsuite/23_containers/array/element_access/110139.cc: New
test.
---
libstdc++-v3/include/std/array | 10 +++++-----
.../23_containers/array/element_access/110139.cc | 5 +++++
2 files changed, 10 insertions(+), 5 deletions(-)
create mode 100644
libstdc++-v3/testsuite/23_containers/array/element_access/110139.cc
diff --git a/libstdc++-v3/include/std/array b/libstdc++-v3/include/std/array
index 27354d9e3fb..70280c1beeb 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__))
- constexpr operator _Tp*() const noexcept { return nullptr; }
+ constexpr explicit operator _Tp*() const noexcept { return nullptr; }
};
using _Is_swappable = true_type;
@@ -240,7 +240,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
front() noexcept
{
__glibcxx_requires_nonempty();
- return _M_elems[0];
+ return _M_elems[(size_type)0];
}
[[__nodiscard__]]
@@ -250,7 +250,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
#if __cplusplus >= 201402L
__glibcxx_requires_nonempty();
#endif
- return _M_elems[0];
+ return _M_elems[(size_type)0];
}
[[__nodiscard__]]
@@ -274,12 +274,12 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
[[__nodiscard__, __gnu__::__const__, __gnu__::__always_inline__]]
_GLIBCXX17_CONSTEXPR pointer
data() noexcept
- { return _M_elems; }
+ { return static_cast<pointer>(_M_elems); }
[[__nodiscard__]]
_GLIBCXX17_CONSTEXPR const_pointer
data() const noexcept
- { return _M_elems; }
+ { return static_cast<const_pointer>(_M_elems); }
};
#if __cpp_deduction_guides >= 201606
diff --git
a/libstdc++-v3/testsuite/23_containers/array/element_access/110139.cc
b/libstdc++-v3/testsuite/23_containers/array/element_access/110139.cc
new file mode 100644
index 00000000000..6f09aacf0a7
--- /dev/null
+++ b/libstdc++-v3/testsuite/23_containers/array/element_access/110139.cc
@@ -0,0 +1,5 @@
+// { dg-options "-pedantic" }
+// { dg-do compile { target c++11 } }
+#include <array>
+template class std::array<int, 0>;
+// { dg-bogus "ambiguous overload" "" { target *-*-* } 0 }
--
2.40.1
