Re: [PATCH] Avoid allocator operator== in _Safe_container

["François Dumont" <frs.dumont@gmail.com>]

[-- Attachment #1: Type: text/plain, Size: 1393 bytes --]

On 09/08/21 1:52 pm, François Dumont wrote:
> On 09/08/21 12:45 pm, Jonathan Wakely wrote:
>> On Mon, 9 Aug 2021 at 11:34, Jonathan Wakely wrote:
>>> On Mon, 9 Aug 2021 at 11:33, Jonathan Wakely wrote:
>>>> On Mon, 9 Aug 2021 at 11:26, François Dumont via Libstdc++
>>>> <libstdc++@gcc.gnu.org> wrote:
>>>>> Some newly introduced tests in
>>>>> 23_containers/unordered_map/cons/default.cc revealed that we are 
>>>>> forcing
>>>>> the allocator type to have a operator==.
>>>> All allocators are required to have operator== so that should not be a
>>>> problem. What is the error?
>>> OK, I see it. I just forgot to define operator== and operator!= for
>>> the custom allocator in that new test, and that should be added.
>> Fixed like this instead. Tested x86_64-linux with -D_GLIBCXX_DEBUG.
>> Pushed to trunk.
>
> Ok, I thought my change was better because we have many allocator 
> types in tests without operator ==/!= (see 
> 23_containers/*/cons/noexcept_default_construct.cc). But of course the 
> tests are not making any use of it for the moment, no big deal.
>
> So this patch is just an optimization, may I still commit it ? Unless 
> you like the fact that Debug mode is checking that those operators are 
> provided when allocator-aware move constructor is being used.
>
>
A simpler version, using _Safe_container move constructor when allocator 
instances are always equals.


[-- Attachment #2: safe_container.patch --]
[-- Type: text/x-patch, Size: 1084 bytes --]

diff --git a/libstdc++-v3/include/debug/safe_container.h b/libstdc++-v3/include/debug/safe_container.h
index d9636c29e9b..97c47167fe8 100644
--- a/libstdc++-v3/include/debug/safe_container.h
+++ b/libstdc++-v3/include/debug/safe_container.h
@@ -57,7 +57,12 @@ namespace __gnu_debug
       _Safe_container(const _Safe_container&) = default;
       _Safe_container(_Safe_container&&) = default;
 
-      _Safe_container(_Safe_container&& __x, const _Alloc& __a)
+    private:
+      _Safe_container(_Safe_container&& __x, const _Alloc&, std::true_type)
+      : _Safe_container(std::move(__x))
+      { }
+
+      _Safe_container(_Safe_container&& __x, const _Alloc& __a, std::false_type)
       : _Safe_container()
       {
 	if (__x._M_cont().get_allocator() == __a)
@@ -65,6 +70,12 @@ namespace __gnu_debug
 	else
 	  __x._M_invalidate_all();
       }
+
+    protected:
+      _Safe_container(_Safe_container&& __x, const _Alloc& __a)
+      : _Safe_container(std::move(__x), __a,
+		      typename std::allocator_traits<_Alloc>::is_always_equal{})
+      { }
 #endif
 
     public: