https://gcc.gnu.org/g:d49d359b0c5266b314bcf31405746909d99927a1
commit r16-2746-gd49d359b0c5266b314bcf31405746909d99927a1
Author: Tomasz Kamiński <tkami...@redhat.com>
Date: Fri Aug 1 09:21:27 2025 +0200
libstdc++: Fix dereferencing of std::indirect xvalues [PR121128]
Forr rvalues the _Self parameter deduces a non-reference type. Consequently,
((_Self)__self) moved the object to a temporary, which then destroyed on
function exit.
This patch fixes this by using a C-style cast __self to (const indirect&).
This not only resolves the above issue but also correctly handles types that
are derived (publicly and privately) from indirect. Allocator requirements
in
[allocator.requirements.general] p22 guarantee that dereferencing const
_M_objp
works with equivalent semantics to dereferencing _M_objp.
PR libstdc++/121128
libstdc++-v3/ChangeLog:
* include/bits/indirect.h (indirect::operator*):
Cast __self to approparietly qualified indirect.
* testsuite/std/memory/indirect/access.cc: New test.
* testsuite/std/memory/polymorphic/access.cc: New test.
Reviewed-by: Jonathan Wakely <jwak...@redhat.com>
Signed-off-by: Tomasz Kamiński <tkami...@redhat.com>
Diff:
---
libstdc++-v3/include/bits/indirect.h | 7 ++-
.../testsuite/std/memory/indirect/access.cc | 58 ++++++++++++++++++++++
.../testsuite/std/memory/polymorphic/access.cc | 53 ++++++++++++++++++++
3 files changed, 116 insertions(+), 2 deletions(-)
diff --git a/libstdc++-v3/include/bits/indirect.h
b/libstdc++-v3/include/bits/indirect.h
index e8000d7c0243..89fa8c874fbd 100644
--- a/libstdc++-v3/include/bits/indirect.h
+++ b/libstdc++-v3/include/bits/indirect.h
@@ -286,8 +286,11 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
constexpr auto&&
operator*(this _Self&& __self) noexcept
{
- __glibcxx_assert(__self._M_objp != nullptr);
- return std::forward_like<_Self>(*((_Self)__self)._M_objp);
+ // n.b. [allocator.requirements.general] p22 implies
+ // dereferencing const pointer is same as pointer
+ const indirect& __iself = (const indirect&)__self;
+ __glibcxx_assert(__iself._M_objp != nullptr);
+ return std::forward_like<_Self>(*__iself._M_objp);
}
constexpr const_pointer
diff --git a/libstdc++-v3/testsuite/std/memory/indirect/access.cc
b/libstdc++-v3/testsuite/std/memory/indirect/access.cc
new file mode 100644
index 000000000000..cf21275a115b
--- /dev/null
+++ b/libstdc++-v3/testsuite/std/memory/indirect/access.cc
@@ -0,0 +1,58 @@
+// { dg-do run { target c++26 } }
+
+#include <memory>
+#include <vector>
+
+#include <testsuite_hooks.h>
+
+template<template<typename> class Indirect>
+constexpr void
+test_access()
+{
+ const std::vector<int> src{1, 2, 3, 4, 5};
+ Indirect<std::vector<int>> i(src);
+ auto const& ci = i;
+ VERIFY( *i == src );
+ VERIFY( *ci == src );
+ VERIFY( *std::move(ci) == src );
+
+ std::vector<int>&& vr = *std::move(i);
+ VERIFY( vr == src );
+ VERIFY( *i == src );
+
+ std::vector<int> vc = *std::move(i);
+ VERIFY( vc == src );
+ VERIFY( vr.empty() );
+ VERIFY( i->empty() );
+ VERIFY( ci->empty() );
+}
+
+template<typename T>
+struct PublicBase : std::indirect<T>
+{
+ using std::indirect<T>::indirect;
+};
+
+template<typename T>
+class PrivateBase : std::indirect<T>
+{
+public:
+ using std::indirect<T>::indirect;
+ using std::indirect<T>::operator*;
+ using std::indirect<T>::operator->;
+};
+
+constexpr bool
+test_all()
+{
+ test_access<std::indirect>();
+ test_access<PublicBase>();
+ test_access<PrivateBase>();
+ return true;
+}
+
+int main()
+{
+ test_all();
+ static_assert(test_all());
+}
diff --git a/libstdc++-v3/testsuite/std/memory/polymorphic/access.cc
b/libstdc++-v3/testsuite/std/memory/polymorphic/access.cc
new file mode 100644
index 000000000000..7b95bb192631
--- /dev/null
+++ b/libstdc++-v3/testsuite/std/memory/polymorphic/access.cc
@@ -0,0 +1,53 @@
+// { dg-do run { target c++26 } }
+
+#include <memory>
+#include <vector>
+
+#include <testsuite_hooks.h>
+
+template<template<typename> class Polymorhpic>
+constexpr void
+test_access()
+{
+ const std::vector<int> src{1, 2, 3, 4, 5};
+ Polymorhpic<std::vector<int>> i(src);
+ auto const& ci = i;
+ VERIFY( *i == src );
+ VERIFY( *ci == src );
+ VERIFY( *std::move(ci) == src );
+
+ auto&& vr = *std::move(i);
+ static_assert( std::is_same_v<decltype(vr), std::vector<int>&> );
+ VERIFY( vr == src );
+ VERIFY( *i == src );
+}
+
+template<typename T>
+struct PublicBase : std::polymorphic<T>
+{
+ using std::polymorphic<T>::polymorphic;
+};
+
+template<typename T>
+class PrivateBase : std::polymorphic<T>
+{
+public:
+ using std::polymorphic<T>::polymorphic;
+ using std::polymorphic<T>::operator*;
+ using std::polymorphic<T>::operator->;
+};
+
+constexpr bool
+test_all()
+{
+ test_access<std::polymorphic>();
+ test_access<PublicBase>();
+ test_access<PrivateBase>();
+ return true;
+}
+
+int main()
+{
+ test_all();
+// static_assert(test_all());
+}
