https://gcc.gnu.org/g:2af87d98e66e57d51f36220de983eff44bae98c8
commit r15-3653-g2af87d98e66e57d51f36220de983eff44bae98c8
Author: Jonathan Wakely <jwak...@redhat.com>
Date: Wed Sep 4 21:31:58 2024 +0100
libstdc++: Adjust std::span::iterator to be ADL-proof
Because std::span<Incomplete> can be useful, it makes sense to define
std::span<Incomplete>::iterator such that Incomplete is not an
associated class, and so the compiler won't attempt to complete it when
doing ADL for span iterators (including during the definition of
std::span<Incomplete>::const_iterator which checks that iterator
satisfies std::input_or_output_iterator).
We can't make this change for std::vector<Incomplete> because it would
change the mangled name of std::vector<Incomplete>::iterator which would
affect the mangled names of templates and functions written by users.
We can do the same thing for std::basic_stacktrace<Alloc> just so that
Alloc is not an associated class. This is probably less beneficial, as
Alloc can't be incomplete, and using SomeAllocator<Incomplete> as the
allocator parameter doesn't seem useful. But simply making the
stacktrace iterator not use Alloc for ADL lookup seems worthwhile. This
is doable because std::stacktrace is part of C++23 so its ABI isn't
considered stable yet.
libstdc++-v3/ChangeLog:
* include/std/span (span::__iter_tag): Declare nested type.
(span::iterator): Use __iter_tag as second template argument.
* include/std/stacktrace (basic_stacktrace::iterator): Use _Impl
as second template argument.
Diff:
---
libstdc++-v3/include/std/span | 5 ++++-
libstdc++-v3/include/std/stacktrace | 4 +++-
2 files changed, 7 insertions(+), 2 deletions(-)
diff --git a/libstdc++-v3/include/std/span b/libstdc++-v3/include/std/span
index 00fc52791526..b7392a0500e9 100644
--- a/libstdc++-v3/include/std/span
+++ b/libstdc++-v3/include/std/span
@@ -123,6 +123,9 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
using __is_compatible_ref
= __is_array_convertible<_Type, remove_reference_t<_Ref>>;
+ // Nested type so that _Type is not an associated class of iterator.
+ struct __iter_tag;
+
public:
// member types
using element_type = _Type;
@@ -133,7 +136,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
using const_pointer = const _Type*;
using reference = element_type&;
using const_reference = const element_type&;
- using iterator = __gnu_cxx::__normal_iterator<pointer, span>;
+ using iterator = __gnu_cxx::__normal_iterator<pointer, __iter_tag>;
using reverse_iterator = std::reverse_iterator<iterator>;
#if __cplusplus > 202002L
using const_iterator = std::const_iterator<iterator>;
diff --git a/libstdc++-v3/include/std/stacktrace
b/libstdc++-v3/include/std/stacktrace
index cd2606257fec..cdd1276d2124 100644
--- a/libstdc++-v3/include/std/stacktrace
+++ b/libstdc++-v3/include/std/stacktrace
@@ -179,13 +179,15 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
{
using _AllocTraits = allocator_traits<_Allocator>;
using uintptr_t = __UINTPTR_TYPE__;
+ struct _Impl;
public:
using value_type = stacktrace_entry;
using const_reference = const value_type&;
using reference = value_type&;
using const_iterator
- = __gnu_cxx::__normal_iterator<value_type*, basic_stacktrace>;
+ = __gnu_cxx::__normal_iterator<typename _AllocTraits::const_pointer,
+ _Impl>;
using iterator = const_iterator;
using reverse_iterator = std::reverse_iterator<iterator>;
using const_reverse_iterator = std::reverse_iterator<const_iterator>;
