custom allocators: define missing 'rebind' type #3895

trofi · 2022-12-20T22:19:43Z

gcc-13 added an assert to standard headers to make sure custom allocators have intended implementation of rebind type instead of inherited rebind. gcc change:
https://gcc.gnu.org/git/?p=gcc.git;a=commitdiff;h=64c986b49558a7

Without the fix build fails on this week's gcc-13 as:

In file included from <<NIX>>-gcc-13.0.0/include/c++/13.0.0/ext/alloc_traits.h:34,
                 from <<NIX>>-gcc-13.0.0/include/c++/13.0.0/bits/basic_string.h:39,
                 from <<NIX>>-gcc-13.0.0/include/c++/13.0.0/string:54,
                 from <<NIX>>-gcc-13.0.0/include/c++/13.0.0/bits/locale_classes.h:40,
                 from <<NIX>>-gcc-13.0.0/include/c++/13.0.0/locale:41,
                 from tests/src/unit-regression2.cpp:19:
<<NIX>>-gcc-13.0.0/include/c++/13.0.0/bits/alloc_traits.h: In instantiation of 'struct std::__allocator_traits_base::__rebind<my_allocator<unsigned char>, unsigned char, void>':
<<NIX>>-gcc-13.0.0/include/c++/13.0.0/bits/alloc_traits.h:94:11:   required by substitution of 'template<class _Alloc, class _Up> using std::__alloc_rebind = typename std::__allocator_traits_base::__rebind<_Alloc, _Up>::type [with _Alloc = my_allocator<unsigned char>; _Up = unsigned char]'
<<NIX>>-gcc-13.0.0/include/c++/13.0.0/bits/alloc_traits.h:228:8:   required by substitution of 'template<class _Alloc> template<class _Tp> using std::allocator_traits< <template-parameter-1-1> >::rebind_alloc = std::__alloc_rebind<_Alloc, _Tp> [with _Tp = unsigned char; _Alloc = my_allocator<unsigned char>]'
<<NIX>>-gcc-13.0.0/include/c++/13.0.0/ext/alloc_traits.h:126:65:   required from 'struct __gnu_cxx::__alloc_traits<my_allocator<unsigned char>, unsigned char>::rebind<unsigned char>'
<<NIX>>-gcc-13.0.0/include/c++/13.0.0/bits/stl_vector.h:88:21:   required from 'struct std::_Vector_base<unsigned char, my_allocator<unsigned char> >'
<<NIX>>-gcc-13.0.0/include/c++/13.0.0/bits/stl_vector.h:423:11:   required from 'class std::vector<unsigned char, my_allocator<unsigned char> >'
tests/src/unit-regression2.cpp:807:63:   required from here
<<NIX>>-gcc-13.0.0/include/c++/13.0.0/bits/alloc_traits.h:70:31: error: static assertion failed: allocator_traits<A>::rebind_alloc<A::value_type> must be A
   70 |                         _Tp>::value,
      |                               ^~~~~

The change adds trivial rebind definition with expected return type.

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coveralls · 2022-12-21T07:20:09Z

Coverage remained the same at 100.0% when pulling a5b09d5 on trofi:gcc-13-rebind-fix into a2f0593 on nlohmann:develop.

`gcc-13` added an assert to standard headers to make sure custom allocators have intended implementation of rebind type instead of inherited rebind. gcc change: https://gcc.gnu.org/git/?p=gcc.git;a=commitdiff;h=64c986b49558a7 Without the fix build fails on this week's `gcc-13` as: In file included from <<NIX>>-gcc-13.0.0/include/c++/13.0.0/ext/alloc_traits.h:34, from <<NIX>>-gcc-13.0.0/include/c++/13.0.0/bits/basic_string.h:39, from <<NIX>>-gcc-13.0.0/include/c++/13.0.0/string:54, from <<NIX>>-gcc-13.0.0/include/c++/13.0.0/bits/locale_classes.h:40, from <<NIX>>-gcc-13.0.0/include/c++/13.0.0/locale:41, from tests/src/unit-regression2.cpp:19: <<NIX>>-gcc-13.0.0/include/c++/13.0.0/bits/alloc_traits.h: In instantiation of 'struct std::__allocator_traits_base::__rebind<my_allocator<unsigned char>, unsigned char, void>': <<NIX>>-gcc-13.0.0/include/c++/13.0.0/bits/alloc_traits.h:94:11: required by substitution of 'template<class _Alloc, class _Up> using std::__alloc_rebind = typename std::__allocator_traits_base::__rebind<_Alloc, _Up>::type [with _Alloc = my_allocator<unsigned char>; _Up = unsigned char]' <<NIX>>-gcc-13.0.0/include/c++/13.0.0/bits/alloc_traits.h:228:8: required by substitution of 'template<class _Alloc> template<class _Tp> using std::allocator_traits< <template-parameter-1-1> >::rebind_alloc = std::__alloc_rebind<_Alloc, _Tp> [with _Tp = unsigned char; _Alloc = my_allocator<unsigned char>]' <<NIX>>-gcc-13.0.0/include/c++/13.0.0/ext/alloc_traits.h:126:65: required from 'struct __gnu_cxx::__alloc_traits<my_allocator<unsigned char>, unsigned char>::rebind<unsigned char>' <<NIX>>-gcc-13.0.0/include/c++/13.0.0/bits/stl_vector.h:88:21: required from 'struct std::_Vector_base<unsigned char, my_allocator<unsigned char> >' <<NIX>>-gcc-13.0.0/include/c++/13.0.0/bits/stl_vector.h:423:11: required from 'class std::vector<unsigned char, my_allocator<unsigned char> >' tests/src/unit-regression2.cpp:807:63: required from here <<NIX>>-gcc-13.0.0/include/c++/13.0.0/bits/alloc_traits.h:70:31: error: static assertion failed: allocator_traits<A>::rebind_alloc<A::value_type> must be A 70 | _Tp>::value, | ^~~~~ The change adds trivial `rebind` definition with expected return type and satisfies conversion requirements.

navinp0304 · 2023-03-06T09:29:12Z

your changes in a5b09d5 is correct. Somehow the rebind part didn't get merged. I created PR #3966 for the missed change.

trofi · 2023-03-06T10:07:04Z

I'm confused. Can you clarify why you need your PR? It looks incomplete compared to this one and will create a conflict if merged.

navinp0304 · 2023-03-06T10:26:46Z

I'm confused. Can you clarify why you need your PR? It looks incomplete compared to this one and will create a conflict if merged.

You haven't pushed the struct rebind other part. I can close my PR if you merge the struct rebind.

trofi · 2023-03-06T11:08:43Z

I'm confused. Can you clarify why you need your PR? It looks incomplete compared to this one and will create a conflict if merged.

You haven't pushed the struct rebind other part. I can close my PR if you merge the struct rebind.

Can you clarify where you expect it to be? https://github.com/nlohmann/json/commit/a5b09d50b786638ed9deb09ef13860a3cb64eb6b.patch does show rebind::other presence for both classes:

diff --git a/tests/src/unit-allocator.cpp b/tests/src/unit-allocator.cpp
index c6b77ed669..c3708e89e3 100644
--- a/tests/src/unit-allocator.cpp
+++ b/tests/src/unit-allocator.cpp
@@ -20,11 +20,20 @@ struct bad_allocator : std::allocator<T>
 {
     using std::allocator<T>::allocator;
 
+    bad_allocator() = default;
+    template<class U> bad_allocator(const bad_allocator<U>& /*unused*/) { }
+
     template<class... Args>
     void construct(T* /*unused*/, Args&& ... /*unused*/)
     {
         throw std::bad_alloc();
     }
+
+    template <class U>
+    struct rebind
+    {
+        using other = bad_allocator<U>;
+    };
 };
 } // namespace
 
--- a/tests/src/unit-regression2.cpp
+++ b/tests/src/unit-regression2.cpp
@@ -187,6 +187,15 @@ class my_allocator : public std::allocator<T>
 {
   public:
     using std::allocator<T>::allocator;
+
+    my_allocator() = default;
+    template<class U> my_allocator(const my_allocator<U>& /*unused*/) { }
+
+    template <class U>
+    struct rebind
+    {
+        using other = my_allocator<U>;
+    };
 };
 
 /////////////////////////////////////////////////////////////////////

Do you expect more code here? Or somewhere else?

navinp0304 · 2023-03-06T11:18:16Z

I'm confused. Can you clarify why you need your PR? It looks incomplete compared to this one and will create a conflict if merged.

You haven't pushed the struct rebind other part. I can close my PR if you merge the struct rebind.

Can you clarify where you expect it to be? https://github.com/nlohmann/json/commit/a5b09d50b786638ed9deb09ef13860a3cb64eb6b.patch does show rebind::other presence for both classes:

Do you expect more code here? Or somewhere else?

See this link https://github.com/nlohmann/json/compare/274f83e115b0e9af8f98f940b927d83455ba419b..a5b09d50b786638ed9deb09ef13860a3cb64eb6b

trofi · 2023-03-06T11:23:59Z

I still don't follow. Sorry.

navinp0304 · 2023-03-06T11:24:40Z

I still don't follow. Sorry.

Are your changes merged to develop branch ?

trofi · 2023-03-06T11:26:11Z

No. This is an open PR against develop branch.

navinp0304 · 2023-03-06T11:39:10Z

No. This is an open PR against develop branch.

Ok, i closed mine. I can confirm your changes work.

nlohmann

Looks good to me.

nlohmann · 2023-03-08T11:31:50Z

Thanks a lot!

trofi requested a review from nlohmann as a code owner December 20, 2022 22:19

github-actions bot added M tests labels Dec 20, 2022

heirecka mentioned this pull request Jan 26, 2023

GCC 13 build failures #3927

Closed

2 tasks

ArsenArsen mentioned this pull request Feb 21, 2023

tests/unit-iterators2: use std::ranges::equals for range comparisons #3950

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nlohmann linked an issue Mar 8, 2023 that may be closed by this pull request

GCC 13 build failures #3927

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nlohmann approved these changes Mar 8, 2023

View reviewed changes

nlohmann added this to the Release 3.11.3 milestone Mar 8, 2023

nlohmann merged commit 6cec5ae into nlohmann:develop Mar 8, 2023

trofi deleted the gcc-13-rebind-fix branch March 8, 2023 16:53

margaridasp mentioned this pull request Oct 19, 2023

Unable to install: fails to build relstorage.cache.cache extension zodb/relstorage#499

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stephengtuggy mentioned this pull request Nov 25, 2023

Troubleshooting Windows Builds 2023-11-24 vegastrike/Vega-Strike-Engine-Source#815

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JSON for Modern C++ 3.11.3 #4222

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custom allocators: define missing 'rebind' type #3895

custom allocators: define missing 'rebind' type #3895

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custom allocators: define missing 'rebind' type #3895

custom allocators: define missing 'rebind' type #3895

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