diff mbox series

libstdc++: Gate constexpr string and vector on constexpr destructor support

Message ID 20220426105232.2059737-1-jwakely@redhat.com
State New
Headers show
Series libstdc++: Gate constexpr string and vector on constexpr destructor support | expand

Commit Message

Jonathan Wakely April 26, 2022, 10:52 a.m. UTC 
I was going to push this patch to "fix" our C++20 constexpr string and
vector so they depend on __cpp_constexpr_dynamic_alloc. But then I
realised that Clang supports that since 10.0.0 and I don't think we need
to bother supporting anything older than that for C++20 mode (Clang 9
users can still use C++17 mode).

So I'm just posting this here for the archives, but I don't plan to
push it. We could probably remove the __cpp_constexpr_dynamic_alloc
checks in std::allocator and std::unique_ptr now too.

-- >8 --

Declaring a destructor as constexpr is only supported when the
__cpp_constexpr_dynamic_alloc macro is defined. Introduce a new macro,
_GLIBCXX_CONSTEXPR_DTOR, which can be used on destructors. Adjust the
relevant feature test macros to also depend on
__cpp_constexpr_dynamic_alloc.

libstdc++-v3/ChangeLog:

	* include/bits/c++config (_GLIBCXX_CONSTEXPR_DTOR): Define new
	macro.
	(_GLIBCXX23_CONSTEXPR_DTOR): Likewise.
	* include/bits/allocator.h (allocator::~allocator()): Use new
	macro.
	* include/bits/basic_string.h (__cpp_lib_constexpr_string):
	Depend on __cpp_constexpr_dynamic_alloc.
	(basic_string::~basic_string()): Use new macro.
	* include/bits/stl_vector.h (__cpp_lib_constexpr_vector):
	Depend on __cpp_constexpr_dynamic_alloc.
	(_Vector_base::~_Vector_base(), vector::~vector()): Use new
	macro.
	* include/bits/unique_ptr.h (unique_ptr, unique_ptr<T[], D>):
	Likewise.
	* include/std/version (__cpp_lib_constexpr_string)
	(__cpp_lib_constexpr_vector): Depend on
	__cpp_constexpr_dynamic_alloc.
---
 libstdc++-v3/include/bits/allocator.h    |  4 +---
 libstdc++-v3/include/bits/basic_string.h | 11 ++++++++---
 libstdc++-v3/include/bits/c++config      | 12 ++++++++++++
 libstdc++-v3/include/bits/stl_vector.h   | 14 ++++++++------
 libstdc++-v3/include/bits/unique_ptr.h   |  8 ++------
 libstdc++-v3/include/std/version         |  6 ++++--
 6 files changed, 35 insertions(+), 20 deletions(-)
diff mbox series

Patch

diff --git a/libstdc++-v3/include/bits/allocator.h b/libstdc++-v3/include/bits/allocator.h
index f7770165273..d94d93546c9 100644
--- a/libstdc++-v3/include/bits/allocator.h
+++ b/libstdc++-v3/include/bits/allocator.h
@@ -168,9 +168,7 @@  _GLIBCXX_BEGIN_NAMESPACE_VERSION
 	_GLIBCXX20_CONSTEXPR
 	allocator(const allocator<_Tp1>&) _GLIBCXX_NOTHROW { }
 
-#if __cpp_constexpr_dynamic_alloc
-      constexpr
-#endif
+      _GLIBCXX_CONSTEXPR_DTOR
       ~allocator() _GLIBCXX_NOTHROW { }
 
 #if __cplusplus > 201703L
diff --git a/libstdc++-v3/include/bits/basic_string.h b/libstdc++-v3/include/bits/basic_string.h
index c3fbc53953c..e5ec7ea794e 100644
--- a/libstdc++-v3/include/bits/basic_string.h
+++ b/libstdc++-v3/include/bits/basic_string.h
@@ -56,9 +56,14 @@  namespace std _GLIBCXX_VISIBILITY(default)
 _GLIBCXX_BEGIN_NAMESPACE_VERSION
 _GLIBCXX_BEGIN_NAMESPACE_CXX11
 
-#ifdef __cpp_lib_is_constant_evaluated
+#if __cpp_lib_is_constant_evaluated
+# if __cpp_constexpr_dynamic_alloc
 // Support P0980R1 in C++20.
-# define __cpp_lib_constexpr_string 201907L
+#  define __cpp_lib_constexpr_string 201907L
+# else
+// Support P1032R1 in C++20.
+#  define __cpp_lib_constexpr_string 201811L
+# endif
 #elif __cplusplus >= 201703L && _GLIBCXX_HAVE_IS_CONSTANT_EVALUATED
 // Support P0426R1 changes to char_traits in C++17.
 # define __cpp_lib_constexpr_string 201611L
@@ -790,7 +795,7 @@  _GLIBCXX_BEGIN_NAMESPACE_CXX11
       /**
        *  @brief  Destroy the string instance.
        */
-      _GLIBCXX20_CONSTEXPR
+      _GLIBCXX_CONSTEXPR_DTOR
       ~basic_string()
       { _M_dispose(); }
 
diff --git a/libstdc++-v3/include/bits/c++config b/libstdc++-v3/include/bits/c++config
index 2798b9786dc..6b575505932 100644
--- a/libstdc++-v3/include/bits/c++config
+++ b/libstdc++-v3/include/bits/c++config
@@ -190,6 +190,18 @@ 
 # endif
 #endif
 
+#ifdef __cpp_constexpr_dynamic_alloc
+# define _GLIBCXX_CONSTEXPR_DTOR constexpr
+#else
+# define _GLIBCXX_CONSTEXPR_DTOR
+#endif
+
+# if __cplusplus >= 202100L
+# define _GLIBCXX23_CONSTEXPR_DTOR _GLIBCXX_CONSTEXPR_DTOR
+#else
+# define _GLIBCXX23_CONSTEXPR_DTOR
+#endif
+
 #ifndef _GLIBCXX17_INLINE
 # if __cplusplus >= 201703L
 #  define _GLIBCXX17_INLINE inline
diff --git a/libstdc++-v3/include/bits/stl_vector.h b/libstdc++-v3/include/bits/stl_vector.h
index b4ff3989a5d..a93018f8700 100644
--- a/libstdc++-v3/include/bits/stl_vector.h
+++ b/libstdc++-v3/include/bits/stl_vector.h
@@ -64,7 +64,9 @@ 
 #endif
 #if __cplusplus >= 202002L
 # include <compare>
-#define __cpp_lib_constexpr_vector 201907L
+# ifdef __cpp_constexpr_dynamic_alloc
+#  define __cpp_lib_constexpr_vector 201907L
+# endif
 #endif
 
 #include <debug/assertions.h>
@@ -229,7 +231,7 @@  _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
 		_S_on_dealloc(_M_impl);
 	      }
 
-	      _GLIBCXX20_CONSTEXPR
+	      _GLIBCXX_CONSTEXPR_DTOR
 	      ~_Reinit()
 	      {
 		// Mark unused capacity as invalid after reallocation.
@@ -254,7 +256,7 @@  _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
 	      : _M_impl(__impl), _M_n(__n)
 	      { _S_grow(_M_impl, __n); }
 
-	      _GLIBCXX20_CONSTEXPR
+	      _GLIBCXX_CONSTEXPR_DTOR
 	      ~_Grow() { if (_M_n) _S_shrink(_M_impl, _M_n); }
 
 	      _GLIBCXX20_CONSTEXPR
@@ -360,7 +362,7 @@  _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
       { }
 #endif
 
-      _GLIBCXX20_CONSTEXPR
+      _GLIBCXX_CONSTEXPR_DTOR
       ~_Vector_base() _GLIBCXX_NOEXCEPT
       {
 	_M_deallocate(_M_impl._M_start,
@@ -724,7 +726,7 @@  _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
        *  not touched in any way.  Managing the pointer is the user's
        *  responsibility.
        */
-      _GLIBCXX20_CONSTEXPR
+      _GLIBCXX_CONSTEXPR_DTOR
       ~vector() _GLIBCXX_NOEXCEPT
       {
 	std::_Destroy(this->_M_impl._M_start, this->_M_impl._M_finish,
@@ -1831,7 +1833,7 @@  _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
 				     std::forward<_Args>(__args)...);
 	  }
 
-	_GLIBCXX20_CONSTEXPR
+	_GLIBCXX_CONSTEXPR_DTOR
 	~_Temporary_value()
 	{ _Alloc_traits::destroy(_M_this->_M_impl, _M_ptr()); }
 
diff --git a/libstdc++-v3/include/bits/unique_ptr.h b/libstdc++-v3/include/bits/unique_ptr.h
index ad60fada59b..a3269ed4f8e 100644
--- a/libstdc++-v3/include/bits/unique_ptr.h
+++ b/libstdc++-v3/include/bits/unique_ptr.h
@@ -384,9 +384,7 @@  _GLIBCXX_BEGIN_NAMESPACE_VERSION
 #endif
 
       /// Destructor, invokes the deleter if the stored pointer is not null.
-#if __cplusplus > 202002L && __cpp_constexpr_dynamic_alloc
-      constexpr
-#endif
+      _GLIBCXX23_CONSTEXPR_DTOR
       ~unique_ptr() noexcept
       {
 	static_assert(__is_invocable<deleter_type&, pointer>::value,
@@ -659,9 +657,7 @@  _GLIBCXX_BEGIN_NAMESPACE_VERSION
 	{ }
 
       /// Destructor, invokes the deleter if the stored pointer is not null.
-#if __cplusplus > 202002L && __cpp_constexpr_dynamic_alloc
-      constexpr
-#endif
+      _GLIBCXX23_CONSTEXPR_DTOR
       ~unique_ptr()
       {
 	auto& __ptr = _M_t._M_ptr();
diff --git a/libstdc++-v3/include/std/version b/libstdc++-v3/include/std/version
index 22280e1a349..ecf4b0a6c4e 100644
--- a/libstdc++-v3/include/std/version
+++ b/libstdc++-v3/include/std/version
@@ -248,7 +248,7 @@ 
 #define __cpp_lib_constexpr_memory 201811L
 #define __cpp_lib_constexpr_numeric 201911L
 #ifdef __cpp_lib_is_constant_evaluated
-# if _GLIBCXX_USE_CXX11_ABI
+# if _GLIBCXX_USE_CXX11_ABI && __cpp_constexpr_dynamic_alloc
 #  define __cpp_lib_constexpr_string 201907L
 # else
 #  define __cpp_lib_constexpr_string 201811L
@@ -257,7 +257,9 @@ 
 #define __cpp_lib_constexpr_string_view 201811L
 #define __cpp_lib_constexpr_tuple 201811L
 #define __cpp_lib_constexpr_utility 201811L
-#define __cpp_lib_constexpr_vector 201907L
+#if __cpp_constexpr_dynamic_alloc
+# define __cpp_lib_constexpr_vector 201907L
+#endif
 #define __cpp_lib_erase_if 202002L
 #define __cpp_lib_generic_unordered_lookup 201811L
 #define __cpp_lib_interpolate 201902L