[PATCH] libstdc++: Fix <memory> for -std=c++23 -ffreestanding [PR114866]

[PATCH] libstdc++: Fix <memory> for -std=c++23 -ffreestanding [PR114866]

[Jonathan Wakely]

Tested x86_64-linux.

It would also be possible to fix this with:

#if ! _GLIBCXX_HOSTED
  template<typename> inline constexpr __is_shared_ptr = false;
#endif

But we would still need to guard the partial specializations that use
shared_ptr and __shared_ptr. It seemed cleaner to just guard all uses of
anything related to shared_ptr so it all goes away for freestanding.

While working on this I noticed that when I added __is_shared_ptr I made
it 'static constexpr' for some reason, rather than 'inline constexpr'.
I'll change that separately.

-- >8 --

std::shared_ptr isn't declared for freestanding, so guard uses of it
with #if _GLIBCXX_HOSTED in <bits/out_ptr.h>.

libstdc++-v3/ChangeLog:

	PR libstdc++/114866
	* include/bits/out_ptr.h [!_GLIBCXX_HOSTED]: Don't refer to
	shared_ptr, __shared_ptr or __is_shred_ptr.
	* testsuite/20_util/headers/memory/114866.cc: New test.
---
 libstdc++-v3/include/bits/out_ptr.h                    | 10 ++++++++++
 .../testsuite/20_util/headers/memory/114866.cc         |  4 ++++
 2 files changed, 14 insertions(+)
 create mode 100644 libstdc++-v3/testsuite/20_util/headers/memory/114866.cc

diff --git a/libstdc++-v3/include/bits/out_ptr.h b/libstdc++-v3/include/bits/out_ptr.h
index aeeb6640441..d74c9f52d3b 100644
--- a/libstdc++-v3/include/bits/out_ptr.h
+++ b/libstdc++-v3/include/bits/out_ptr.h
@@ -54,9 +54,11 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
   template<typename _Smart, typename _Pointer, typename... _Args>
     class out_ptr_t
     {
+#if _GLIBCXX_HOSTED
       static_assert(!__is_shared_ptr<_Smart> || sizeof...(_Args) != 0,
 		    "a deleter must be used when adapting std::shared_ptr "
 		    "with std::out_ptr");
+#endif
 
     public:
       explicit
@@ -216,6 +218,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 	  [[no_unique_address]] _Del2 _M_del;
 	};
 
+#if _GLIBCXX_HOSTED
       // Partial specialization for std::shared_ptr.
       // This specialization gives direct access to the private member
       // of the shared_ptr, avoiding the overhead of storing a separate
@@ -274,6 +277,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 	{
 	  using _Impl<_Smart, _Pointer, _Del, allocator<void>>::_Impl;
 	};
+#endif
 
       using _Impl_t = _Impl<_Smart, _Pointer, _Args...>;
 
@@ -293,8 +297,10 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
   template<typename _Smart, typename _Pointer, typename... _Args>
     class inout_ptr_t
     {
+#if _GLIBCXX_HOSTED
       static_assert(!__is_shared_ptr<_Smart>,
 		    "std::inout_ptr can not be used to wrap std::shared_ptr");
+#endif
 
     public:
       explicit
@@ -320,11 +326,15 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
       }
 
     private:
+#if _GLIBCXX_HOSTED
       // Avoid an invalid instantiation of out_ptr_t<shared_ptr<T>, ...>
       using _Out_ptr_t
 	= __conditional_t<__is_shared_ptr<_Smart>,
 			  out_ptr_t<void*, void*>,
 			  out_ptr_t<_Smart, _Pointer, _Args...>>;
+#else
+      using _Out_ptr_t = out_ptr_t<_Smart, _Pointer, _Args...>;
+#endif
       using _Impl_t = typename _Out_ptr_t::_Impl_t;
       _Impl_t _M_impl;
     };
diff --git a/libstdc++-v3/testsuite/20_util/headers/memory/114866.cc b/libstdc++-v3/testsuite/20_util/headers/memory/114866.cc
new file mode 100644
index 00000000000..7cf6be0539d
--- /dev/null
+++ b/libstdc++-v3/testsuite/20_util/headers/memory/114866.cc
@@ -0,0 +1,4 @@
+// { dg-options "-ffreestanding" }
+// { dg-do compile }
+// PR libstdc++/114866 <memory> & out_ptr in freestanding
+#include <memory>
-- 
2.44.0