On Thu, 02 Jul 2026 at 14:22 +0200, Tomasz Kamiński wrote:
This implements the remaining part of P3981R2 Better return types
in std::inplace_vector and std::exception_ptr_cast.
For the following functions that are defined out of line in
<optional> header, that header must be included before their
use:
* value - throw bad_optional_access, and would cause cyclic include
of <exception>,
* transform, and_then - couldn't be used with function that
returns value (wrapped) in optional, as they would instantiate
primary specialization
* or_else - reintroduce dependency of bits/invoke.h
* begin/end - dependency or normal_iterator from bits/stl_iterator.h.
The value_or was also defined out of line for consistency, I think
it would be confisuing if calling value/transform requires <optional>
include, but not value_or.
This patch also introduce _S_from_ptr function to optional<T&>, that
allows it to be constructed from pointer, without need to check for
null. This function is public, as I believe it will be usefull in more
places.
libstdc++-v3/ChangeLog:
* include/bits/optional_ref.h (optional<_Tp&>::_S_from_ptr):
Define.
* include/bits/version.def (exception_ptr_cast): Bump value
to 202603.
* include/bits/version.h: Regenerate.
* libsupc++/exception_ptr.h (exception_ptr_cast)
[__cpp_lib_exception_ptr_cast >= 202603L]: Change return
type to optional<const _Ex&>.
* testsuite/18_support/exception_ptr/exception_ptr_cast.cc:
Modify to handle change in the return type, and add test
for type convertible to optional to reference to that value.
---
Testing on x86_64-linux. All test passed locally.
OK for trunk when exteded suite happens?
libstdc++-v3/include/bits/optional_ref.h | 8 ++++
libstdc++-v3/include/bits/version.def | 4 +-
libstdc++-v3/include/bits/version.h | 4 +-
libstdc++-v3/libsupc++/exception_ptr.h | 21 +++++----
.../exception_ptr/exception_ptr_cast.cc | 47 ++++++++++++++-----
5 files changed, 60 insertions(+), 24 deletions(-)
diff --git a/libstdc++-v3/include/bits/optional_ref.h
b/libstdc++-v3/include/bits/optional_ref.h
index e018a4199e9..bc01d271a9a 100644
--- a/libstdc++-v3/include/bits/optional_ref.h
+++ b/libstdc++-v3/include/bits/optional_ref.h
@@ -132,6 +132,14 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
public:
using value_type = _Tp;
+ constexpr static optional
+ _S_from_ptr(_Tp* __ptr)
I don't love this being a public member, but OK for trunk.
+ {
+ optional __res;
+ __res._M_val = __ptr;
+ return __res;
+ }
+
// Constructors.
constexpr optional() noexcept = default;
constexpr optional(nullopt_t) noexcept : optional() {}
diff --git a/libstdc++-v3/include/bits/version.def
b/libstdc++-v3/include/bits/version.def
index cb48380e2fa..f47df2a0fb8 100644
--- a/libstdc++-v3/include/bits/version.def
+++ b/libstdc++-v3/include/bits/version.def
@@ -2339,9 +2339,11 @@ ftms = {
};
ftms = {
+ // 202506 P2927R3 Observing exceptions stored in exception_ptr
+ // 202603 P3981R2 Better return types in std::inplace_vector and
std::exception_ptr_cast
name = exception_ptr_cast;
values = {
- v = 202506;
+ v = 202603;
cxxmin = 26;
};
};
diff --git a/libstdc++-v3/include/bits/version.h
b/libstdc++-v3/include/bits/version.h
index c20c3d18535..05ded7cd7bd 100644
--- a/libstdc++-v3/include/bits/version.h
+++ b/libstdc++-v3/include/bits/version.h
@@ -2588,9 +2588,9 @@
#if !defined(__cpp_lib_exception_ptr_cast)
# if (__cplusplus > 202302L)
-# define __glibcxx_exception_ptr_cast 202506L
+# define __glibcxx_exception_ptr_cast 202603L
# if defined(__glibcxx_want_all) || defined(__glibcxx_want_exception_ptr_cast)
-# define __cpp_lib_exception_ptr_cast 202506L
+# define __cpp_lib_exception_ptr_cast 202603L
# endif
# endif
#endif /* !defined(__cpp_lib_exception_ptr_cast) */
diff --git a/libstdc++-v3/libsupc++/exception_ptr.h
b/libstdc++-v3/libsupc++/exception_ptr.h
index 61ab0203fa0..81efe49be1f 100644
--- a/libstdc++-v3/libsupc++/exception_ptr.h
+++ b/libstdc++-v3/libsupc++/exception_ptr.h
@@ -41,6 +41,10 @@
# include <bits/move.h>
#endif
+#if __cpp_lib_exception_ptr_cast >= 202603L
+# include <bits/optional_ref.h>
+#endif
+
#ifdef _GLIBCXX_EH_PTR_RELOPS_COMPAT
# define _GLIBCXX_EH_PTR_USED __attribute__((__used__))
#else
@@ -81,9 +85,9 @@ namespace std _GLIBCXX_VISIBILITY(default)
/// Throw the object pointed to by the exception_ptr.
void rethrow_exception(exception_ptr) __attribute__ ((__noreturn__));
-#if __cpp_lib_exception_ptr_cast >= 202506L
+#if __cpp_lib_exception_ptr_cast >= 202603L
template<typename _Ex>
- constexpr const _Ex* exception_ptr_cast(const exception_ptr&) noexcept;
+ constexpr optional<const _Ex&> exception_ptr_cast(const exception_ptr&)
noexcept;
template<typename _Ex>
void exception_ptr_cast(const exception_ptr&&) = delete;
#endif
@@ -139,7 +143,7 @@ namespace std _GLIBCXX_VISIBILITY(default)
_GLIBCXX_USE_NOEXCEPT;
#if __cpp_lib_exception_ptr_cast >= 202506L
template<typename _Ex>
- friend constexpr const _Ex*
+ friend constexpr optional<const _Ex&>
std::exception_ptr_cast(const exception_ptr&) noexcept;
#endif
@@ -352,10 +356,10 @@ namespace std _GLIBCXX_VISIBILITY(default)
return exception_ptr();
}
-#if __cpp_lib_exception_ptr_cast >= 202506L
+#if __cpp_lib_exception_ptr_cast >= 202603L
template<typename _Ex>
[[__gnu__::__always_inline__]]
- constexpr const _Ex*
+ constexpr optional<const _Ex&>
exception_ptr_cast(const exception_ptr& __p) noexcept
{
static_assert(!std::is_const_v<_Ex>);
@@ -369,7 +373,8 @@ namespace std _GLIBCXX_VISIBILITY(default)
// For runtime calls with -frtti enabled we can avoid try-catch overhead.
if ! consteval {
const type_info &__id = typeid(const _Ex&);
- return static_cast<const _Ex*>(__p._M_exception_ptr_cast(__id));
+ const _Ex* __exp = static_cast<const
_Ex*>(__p._M_exception_ptr_cast(__id));
+ return optional<const _Ex&>::_S_from_ptr(__exp);
}
#endif
@@ -381,14 +386,14 @@ namespace std _GLIBCXX_VISIBILITY(default)
}
catch (const _Ex& __exc)
{
- return &__exc;
+ return optional<const _Ex&>(std::in_place, __exc);
}
catch (...)
{
}
#endif
- return nullptr;
+ return std::nullopt;
}
#endif
diff --git
a/libstdc++-v3/testsuite/18_support/exception_ptr/exception_ptr_cast.cc
b/libstdc++-v3/testsuite/18_support/exception_ptr/exception_ptr_cast.cc
index 3c40bef36a4..1b980a32362 100644
--- a/libstdc++-v3/testsuite/18_support/exception_ptr/exception_ptr_cast.cc
+++ b/libstdc++-v3/testsuite/18_support/exception_ptr/exception_ptr_cast.cc
@@ -22,8 +22,8 @@
#include <exception>
#include <testsuite_hooks.h>
-#if __cpp_lib_exception_ptr_cast != 202506L
-# error "__cpp_lib_exception_ptr_cast != 202506"
+#if __cpp_lib_exception_ptr_cast != 202603L
+# error "__cpp_lib_exception_ptr_cast != 202606"
#endif
struct A { int a; };
@@ -36,22 +36,33 @@ struct G : virtual F, virtual C, virtual E {
constexpr G () : g (4) { a = 1; e = 2; f = 3; } int g;
};
+// Convertible to optional<const Y&>
+struct Y
+{
+ constexpr operator std::optional<const Y&>() const
+ { return std::nullopt; }
+};
+
constexpr bool test01(bool x)
{
auto a = std::make_exception_ptr(C{ 42 });
auto b = std::exception_ptr_cast<C>(a);
- VERIFY( b != nullptr );
+ auto bp = &*b;
+ VERIFY( b );
VERIFY( b->a == 42 );
auto c = std::exception_ptr_cast<B>(a);
- VERIFY( c == static_cast<const B*>(b) );
+ VERIFY( c );
+ VERIFY( &*c == static_cast<const B*>(bp) );
auto d = std::exception_ptr_cast<A>(a);
- VERIFY( d == static_cast<const A*>(b) );
+ VERIFY( d );
+ VERIFY( &*d == static_cast<const A*>(bp) );
auto e = std::exception_ptr_cast<D>(a);
- VERIFY( e == nullptr );
+ VERIFY( !e );
auto f = std::make_exception_ptr(42L);
auto g = std::exception_ptr_cast<long>(f);
- VERIFY( g != nullptr );
+ VERIFY( g );
VERIFY( *g == 42L );
+
try
{
throw G ();
@@ -64,19 +75,29 @@ constexpr bool test01(bool x)
auto h = std::current_exception();
#endif
auto i = std::exception_ptr_cast<G>(h);
- VERIFY( i != nullptr );
+ VERIFY( i );
VERIFY( i->a == 1 && i->e == 2 && i->f == 3 && i->g == 4 );
+ auto ip = &*i;
auto j = std::exception_ptr_cast<A>(h);
- VERIFY( j == static_cast<const A*>(i) );
+ VERIFY( j );
+ VERIFY( &*j == static_cast<const A*>(ip) );
auto k = std::exception_ptr_cast<C>(h);
- VERIFY( k == static_cast<const C*>(i) );
+ VERIFY( k );
+ VERIFY( &*k == static_cast<const C*>(ip) );
auto l = std::exception_ptr_cast<E>(h);
- VERIFY( l == static_cast<const E*>(i) );
+ VERIFY( l );
+ VERIFY( &*l == static_cast<const E*>(ip) );
auto m = std::exception_ptr_cast<F>(h);
- VERIFY( m == static_cast<const F*>(i) );
+ VERIFY( m );
+ VERIFY( &*m == static_cast<const F*>(ip) );
auto n = std::exception_ptr_cast<G>(a);
- VERIFY( n == nullptr );
+ VERIFY( !n );
}
+
+ auto o = std::make_exception_ptr(Y{});
+ auto p = std::exception_ptr_cast<Y>(o);
+ VERIFY( p );
+
if (x)
throw 1;
return true;
--
2.54.0
