From f927694fe168a805eecee8c83407e4aa3d3b5b0c Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Dietmar=20K=C3=BChl?= <dietmar.kuehl@me.com>
Date: Sun, 25 Jan 2026 22:15:41 +0000
Subject: [PATCH 01/12] add a paper on task allocation

---
 docs/Makefile                |   2 +-
 docs/P3941-affinity.md       |   2 +-
 docs/P3980-allocation.md     | 464 +++++++++++++++++++++++++++++++++++
 docs/task-issues.md          |  28 +++
 examples/issue-affine_on.cpp |   2 -
 5 files changed, 494 insertions(+), 4 deletions(-)
 create mode 100644 docs/P3980-allocation.md
 create mode 100644 docs/task-issues.md

diff --git a/docs/Makefile b/docs/Makefile
index 9594236..36b9db4 100644
--- a/docs/Makefile
+++ b/docs/Makefile
@@ -4,7 +4,7 @@ default: doc
 
 doc: doc-html
 
-doc-html: P3552-task.html P3796-task-issues.html P3941-affinity.html
+doc-html: P3552-task.html P3796-task-issues.html P3941-affinity.html P3980-allocation.html
 
 doc-pdf: P3552-task.pdf P3796-task-issues.pdf
 
diff --git a/docs/P3941-affinity.md b/docs/P3941-affinity.md
index d697289..c012a78 100644
--- a/docs/P3941-affinity.md
+++ b/docs/P3941-affinity.md
@@ -10,7 +10,7 @@ author:
     - name: Dietmar Kühl (Bloomberg)
       email: <dkuhl@bloomberg.net>
 source:
-    - https://github.com/bemanproject/task/doc/issues.md
+    - https://github.com/bemanproject/task/doc/P3941-affinity.md
 toc: true
 ---
 
diff --git a/docs/P3980-allocation.md b/docs/P3980-allocation.md
new file mode 100644
index 0000000..b0b21cf
--- /dev/null
+++ b/docs/P3980-allocation.md
@@ -0,0 +1,464 @@
+---
+title: Task's Allocator Use
+document: D3980R0
+date: 2026-01-25
+audience:
+    - Library Evolution Working Group (LEWG)
+    - Library Working Group (LWG)
+author:
+    - name: Dietmar Kühl (Bloomberg)
+      email: <dkuhl@bloomberg.net>
+source:
+    - https://github.com/bemanproject/task/doc/P3980-allocation.md
+toc: true
+---
+
+<p>
+There are different uses of allocators for `task`. The obvious use
+is that the coroutine frame needs to be allocated and using an
+allocator control where this coroutine frame gets allocated. In
+addition, the environment used when `connect`ing a sender can provide
+access to an allocator via the `get_allocator` query. The current
+specification uses the same allocator for coroutine frame and the
+child environments. At the Kona meeting the room preferred if these
+were separated and the allocator for the environment were taken
+from the environment of the receiver it gets `connect`ed to. In
+doing so, the allocator for the coroutine frame becomes more flexible
+and it should be brought more in line with `generator`'s allocator
+use. This paper addresses
+[US 254-385](https://github.com/cplusplus/nbballot/issues/960),
+[US 253-386](https://github.com/cplusplus/nbballot/issues/961),
+[US 255-384](https://github.com/cplusplus/nbballot/issues/959),
+and [US 261-391](https://github.com/cplusplus/nbballot/issues/966).
+</p>
+
+# Change History
+
+## R0 Initial Revision
+
+# Overview of Changes
+
+<p>
+There are a few NB comments about `task`'s use of allocators:
+</p>
+<ul>
+<li>[US 254-385](https://github.com/cplusplus/nbballot/issues/960): Constraint `allocator_arg` argument to be the first argument</li>
+<li>[US 253-386](https://github.com/cplusplus/nbballot/issues/961): Allow use of arbitrary allocators for coroutine frame</li>
+<li>[US 255-384](https://github.com/cplusplus/nbballot/issues/959): Use allocator from receiver's environment </li>
+<li>[US 261-391](https://github.com/cplusplus/nbballot/issues/966): Bad specification of parameter type</li>
+</ul>
+<p>
+The first issue
+([US 254-385](https://github.com/cplusplus/nbballot/issues/960)) is
+about where an allocator argument for the coroutine frame may go
+on the coroutine function.  The options are a fixed location (which
+would first for consistency with existing use) and anywhere. The
+status quo is anywhere and the request is to require that it goes
+first. However, to support optionally passing an allocator having
+it go anywhere is easier to do.
+</p>
+<p>
+The allocator constraints for allocating the coroutine frame are
+due to the use of the same allocator for the environment of child
+senders. If the allocator for the environment of child senders uses
+the allocator from the receiver's environment, these constraints
+can be relaxed. Instead, there may be requirements on the result
+of the `get_allocator` query from the receiver's environment. The
+discussion in Kona favored this direction. This change can address
+the second ([US 253-386](https://github.com/cplusplus/nbballot/issues/961))
+and the third
+([US 255-384](https://github.com/cplusplus/nbballot/issues/959)) issues.
+</p>
+<p>
+The forth issue ([US
+261-391](https://github.com/cplusplus/nbballot/issues/966)) is
+primarily a wording issue. However, some of the problematic paragraphs
+will need some modifications to address the other issues, i.e., fixing
+these wording issues in isolation isn't reasonable.
+</p>
+
+# Allocator Argument Position
+
+<p>
+The combination of using `allocator_arg` followed by an allocator
+object when invoking a function or a constructor is used in various
+places throughout the standard C++ library. The `allocator_arg`
+argument normally needs to be the first argument when present. The
+definition of `task` makes the position of the `allocator_arg` more
+flexible to allow easier support for optionally passing an allocator.
+</p>
+<p>
+For coroutines, the arguments to the coroutine [factory] function
+show up in three separate places:
+</p>
+<ol>
+<li>The parameters to the coroutine [factory] functions.</li>
+<li>The constructor of the `promise_type` if there is a suitable matching overload.</li>
+<li>the `operator new()` of the `promise_type` if there is a suitable matching overload.</li>
+</ol>
+<p>
+This added flexibility doesn't introduce any constraints on how the coroutine
+function is defined. It rather allows passing an `allocator_arg`/allocator
+pair without requiring a specific location. The main benefit is that support
+of an optional allocator can be supported by having a trailing `, auto&&...`
+on the parameter list. Note that the allocator used for the coroutine frame
+is normally not used in the body of the allocator. If it is needed, it can
+in all cases be put into the first location.
+</p>
+::: cmptable
+
+### First
+```
+task<> none(int x)
+{ ...  }
+```
+
+### Flexible
+```
+task<> none(int x)
+{ ...  }
+```
+
+---
+
+```
+task<> comes_first(allocator_arg_t, auto a, int x)
+{ ...  }
+```
+
+```
+task<> comes_first(allocator_arg_t, auto a, int x)
+{ ...  }
+```
+
+---
+
+```
+task<> optional(allocator_arg_t, auto, int x)
+{ ... }
+task<> optional(int x)
+{ return optional(allocator_arg, allocator<char>(), x); }
+```
+
+```
+task<> optional(int x, auto&&...)
+{ ... }
+```
+
+:::
+
+<p>
+The comparison table above shows three separate cases the author of
+a coroutine function may want to support:
+</p>
+<ol>
+  <li>No allocator support (`none`): the use identical and just doesn't mention any allocator.</li>
+  <li>Mandate that the allocator is the first argument (`comes_first`): the use is identical.</li>
+  <li>
+    Support optionally passing an `allocator_arg`/allocator pair
+    (`optional`): the use can be identical but it can also be simplied
+    taking advantage of the flexible location.
+  </li>
+</ol>
+
+Below are three variations of the wording changes, only one can be picked:
+
+<ol type="A">
+<li>Only support `allocator_arg` as the first argument and use the receiver's allocator for the environment.</li>
+<li>Flexible position of the allocator arg and use allocator for the environment.</li>
+<li>Flexible position of the allocator arg and use the receiver's allocator for the environment.</li>
+</ol>
+
+## Wording Change A: `allocator_arg` must be first argument
+
+::: ednote
+Change the synopsis of `promise` type in [task.promise], modifying
+the overloads of `operator new`:
+:::
+
+```
+namespace std::execution {
+  template<class T, class Environment>
+  class task<T, Environment>::promise_type {
+  public:
+    ...
+    unspecified get_env() const noexcept;
+
+    @[void*]{.add}@ @[operator]{.add}@ @[new(size_t]{.add}@ @[size);]{.add}@
+    template<@[class Alloc,]{.add}@ class... Args>
+      void* operator new(size_t size, @[allocator_arg_t,]{.add}@ @[Alloc]{.add}@ @[alloc, ]{.add}@Args&&... @[args]{.rm}@);
+
+    void operator delete(void* pointer, size_t size) noexcept;
+
+  private:
+    ...
+  };
+}
+```
+
+::: ednote
+Change [task.promise] paragraphs 17 and 18:
+:::
+
+::: add
+
+```
+void* operator new(size_t size);
+```
+
+[??]{.pnum} _Returns_: `operator new(size, allocator_arg, allocator<byte>());`
+
+:::
+
+```
+template<@[class Alloc,]{.add}@ class... Args>
+  void* operator new(size_t size, @[allocator_arg_t,]{.add}@ @[Alloc]{.add}@ @[alloc, ]{.add}@Args&&... @[args]{.rm}@);
+```
+
+[17]{.pnum} [If there is no parameter with type `allocator_arg_t`
+then let `alloc` be `allocator_type()`. Otherwise, let `arg_next`
+be the parameter following the first `allocator_arg_t` parameter,
+and let `alloc` be `allocator_type(arg_next)`]{.rm}. Let `PAlloc`
+be `allocator_traits<@[allocator_type]{.rm}@@[Alloc]{.add}@>::template
+rebind_alloc<U>`, where `U` is an unspecified type whose size and
+alignment are both `__STDCPP_DEFAULT_NEW_ALIGNMENT__`.
+
+::: rm
+
+[18]{.pnum}
+_Mandates_:
+
+<ul>
+<li>[18.1]{.pnum} The first parameter of type `allocator_arg_t` (if any) is not the last parameter.</li>
+<li>[18.2]{.pnum} `allocator_type(arg_next)` is a valid expression if there is a parameter of type `allocator_arg_t`.</li>
+<li>[18.3]{.pnum} `allocator_traits<PAlloc>​::​pointer` is a pointer type.</li>
+</ul>
+
+:::
+
+::: add
+
+[18]{.pnum}
+_Mandates_: `allocator_traits<PAlloc>​::​pointer` is a pointer type.
+
+:::
+
+[19]{.pnum} _Effects_: Initializes an allocator `palloc` of type
+`PAlloc` with `alloc`. Uses `palloc` to allocate storage for the
+smallest array of `U` sufficient to provide storage for a coroutine
+state of size `size`, and unspecified additional state necessary to
+ensure that `operator delete` can later deallocate this memory block
+with an allocator equal to `palloc`.
+
+[20]{.pnum} _Returns_: A pointer to the allocated storage.
+
+## Wording Change B: Fix type names, allow flexible position, use for env
+
+::: ednote
+
+Change [task.promise] pargraph 17 and 18 to use the correct type:
+
+:::
+
+```
+template<class... Args>
+  void* operator new(size_t size, Args&&... args);
+```
+
+[17]{.pnum} If there is no parameter with type `@[allocator_arg_t]{.rm}@@[const]{.add}@ @[allocator_arg_t&]{.add}@`
+then let `alloc` be `allocator_type()`. Otherwise, let `arg_next`
+be the parameter following the first `@[allocator_arg_t]{.rm}@@[const]{.add}@ @[allocator_arg_t&]{.add}@` parameter,
+and let `alloc` be `allocator_type(arg_next)`. Let `PAlloc`
+be `allocator_traits<allocator_type>::template
+rebind_alloc<U>`, where `U` is an unspecified type whose size and
+alignment are both `__STDCPP_DEFAULT_NEW_ALIGNMENT__`.
+
+[18]{.pnum}
+_Mandates_:
+
+<ul>
+<li>[18.1]{.pnum} The first parameter of type `@[allocator_arg_t]{.rm}@@[const]{.add}@ @[allocator_arg_t&]{.add}@` (if any) is not the last parameter.</li>
+<li>[18.2]{.pnum} `allocator_type(arg_next)` is a valid expression if there is a parameter of type `allocator_arg_t`.</li>
+<li>[18.3]{.pnum} `allocator_traits<PAlloc>​::​pointer` is a pointer type.</li>
+</ul>
+
+[19]{.pnum} _Effects_: Initializes an allocator `palloc` of type
+`PAlloc` with `alloc`. Uses `palloc` to allocate storage for the
+smallest array of `U` sufficient to provide storage for a coroutine
+state of size `size`, and unspecified additional state necessary to
+ensure that `operator delete` can later deallocate this memory block
+with an allocator equal to `palloc`.
+
+[20]{.pnum} _Returns_: A pointer to the allocated storage.
+
+## Wording Change C: Fix type names, allow flexible position, don't use for env
+
+::: ednote
+
+Change [task.promise] pargraph 17 and 18 to use the correct type and don't convert to `allocator_type`:
+
+:::
+
+```
+template<class... Args>
+  void* operator new(size_t size, Args&&... args);
+```
+
+[17]{.pnum} If there is no parameter with type `@[allocator_arg_t]{.rm}@@[const]{.add}@ @[allocator_arg_t&]{.add}@`
+then let `alloc` be `@[allocator_type()]{.rm}@@[allocator<byte>()]{.add}@`. Otherwise, let `@[arg_next]{.rm}@@[alloc]{.add}@`
+be the parameter following the first `@[allocator_arg_t]{.rm}@@[const]{.add}@ @[allocator_arg_t&]{.add}@`
+parameter[, and let `alloc` be `allocator_type(arg_next)`]{.rm}. Let `PAlloc`
+be `allocator_traits<@[allocator_type]{.rm}@@[remove_cvref_t<decltype(alloc)>]{.add}@>::template rebind_alloc<U>`, where `U` is an unspecified type whose size and
+alignment are both `__STDCPP_DEFAULT_NEW_ALIGNMENT__`.
+
+[18]{.pnum}
+_Mandates_:
+
+<ul>
+<li>[18.1]{.pnum} The first parameter of type `@[allocator_arg_t]{.rm}@@[const]{.add}@ @[allocator_arg_t&]{.add}@` (if any) is not the last parameter.</li>
+
+<li>
+::: rm
+[18.2]{.pnum} `allocator_type(arg_next)` is a valid expression if there is a parameter of type `allocator_arg_t`.
+:::
+</li>
+
+<li>[18.3]{.pnum} `allocator_traits<PAlloc>​::​pointer` is a pointer type.</li>
+</ul>
+
+[19]{.pnum} _Effects_: Initializes an allocator `palloc` of type
+`PAlloc` with `alloc`. Uses `palloc` to allocate storage for the
+smallest array of `U` sufficient to provide storage for a coroutine
+state of size `size`, and unspecified additional state necessary to
+ensure that `operator delete` can later deallocate this memory block
+with an allocator equal to `palloc`.
+
+[20]{.pnum} _Returns_: A pointer to the allocated storage.
+
+# Use Allocator From Environment
+
+<p>
+During the discussion at Kona the conclusion was that the allocator
+forwarded by `task`'s environment to child senders should be the
+allocator from `get_allocator` on the receiver `task` gets `connect`ed
+to. Let `rcvr` be the receiver a `task` got `connect`ed to and let `ev`
+be the result of `get_env(rcvr)`. The implication is that the `task`'s
+`allocator_type` is compatible with the allocator of `ev`:
+</p>
+<ul>
+  <li>
+    If `get_allocator(ev)` is not defined, `allocator_type` has to
+    be default constructible.
+  </li>
+  <li>
+    Otherwise `allocator_type(get_allocator(ev))` has to be well-formed.
+  </li>
+  <li>
+    There is no need to store an <code><i>alloc</i></code> in the 
+    `promise_type`: it can be obtained when requested from `ev` which,
+    in turn, can be obtained from `rcvr`. Thus, the ctor for `promise_type`
+    isn't needed.
+  </li>
+  <li>
+    The definition of `get_env` needs to be changed to get the allocator
+    when needed.
+  </li>
+</ul>
+
+## Wording Changes
+
+::: ednote
+
+In [[task.members](https://wg21.link/task.members#3)] add a _Mandates_ to `connect`:
+
+:::
+
+```
+template<receiver Rcvr>
+  state<Rcvr> connect(Rcvr&& recv) &&;
+```
+
+::: add
+
+[?]{.pnum} _Mandates_: `allocator_type(get_allocator(get_env(rcvr)))` is well-formed or `allocator_type()` is well-formed.
+
+:::
+
+[3]{.pnum} _Preconditions_: <code>bool(<i>handle</i>)</code> is `true`.
+
+[4]{.pnum} _Effects_: Equivalent to:
+```
+return state<Rcvr>(exchange(handle, {}), std::forward<Rcvr>(recv));
+```
+
+::: ednote
+
+In [[task.promise]](https://wg21.link/task.promise) in the synopsis remove the `promise_type` constructor and
+the <code><i>alloc</i></code> exposition-only member.
+
+:::
+
+```
+namespace std::execution {
+  template<class T, class Environment>
+  class task<T, Environment>::promise_type {
+  public:
+    @[template<class...]{.rm}@ @[Args>]{.rm}@
+      @[promise_type(const]{.rm}@ @[Args&...]{.rm}@ @[args);]{.rm}@
+
+    task get_return_object() noexcept;
+
+    ...
+  private:
+    using error-variant = see below;    // @_exposition only_@
+
+    @[allocator_type]{.rm}@    @[_alloc_;]{.rm}@            @[//]{.rm}@ @[_exposition_]{.rm}@ @[_only_]{.rm}@
+    stop_source_type  @_source_@;           // @_exposition only_@
+    stop_token_type   @_token_@;            // @_exposition only_@
+    optional<T>       @_result_@;           // @_exposition only_@; present only if is_void_v<T> is false
+    error-variant     @_errors_@;           // @_exposition only_@
+  };
+}
+```
+
+::: ednote
+
+Remove the ctor for `promise_type`, i.e., [[task.promise]](https://wg21.link/task.promise) paragraph [3](https://wg21.link/task.promise#3) and [4](https://wg21.link/task.promise#4):
+
+:::
+
+::: rm
+
+```
+template<class... Args>
+  promise_type(const Args&... args);
+```
+
+[3]{.pnum} _Mandates_: The first parameter of type `allocator_arg_t`
+(if any) is not the last parameter.
+
+[4]{.pnum} _Effects_: If `Args` contains an element of type
+`allocator_arg_t` then <code><i>alloc</i></code> is initialized
+with the corresponding next element of `args`. Otherwise,
+<code><i>alloc</i></code> is initialized with `allocator_type()`.
+
+:::
+
+::: ednote
+
+Change `get_env` to get the allocator from the receiver when needed
+in [[task.promise] p16](https://wg21.link/task.pomise#16):
+
+:::
+
+```
+@_unspecified_@ get_env() const noexcept;
+```
+
+[16]{.pnum} _Returns_: An object `env` such that queries are forwarded as follows:
+<ul>
+<li>[16.1]{.pnum} `env.query(get_scheduler)` returns <code>scheduler_type(<i>SCHED</i>(*this))</code>.</li>
+<li>[16.2]{.pnum} `env.query(get_allocator)` returns [<code><i>alloc</i></code>]{.rm}[<code>allocator_type(get_allocator(get_env(<i>RCVR</i>(*this))))</code> if this expression is well-formed and `allocator_type()` otherwise]{.add}.</li>
+<li>[16.3]{.pnum} `env.query(get_stop_token)` returns <code><i>token</i></code>.</li>
+<li>[16.4]{.pnum} For any other query `q` and arguments `a...` a call to `env.query(q, a...)` returns <code><i>STATE</i>(*this).environment.query(q, a...)</code> if this expression is well-formed and `forwarding_query(q)` is well-formed and is `true`. Otherwise `env.query(q, a...)` is ill-formed.</li>
+</ul>
diff --git a/docs/task-issues.md b/docs/task-issues.md
new file mode 100644
index 0000000..e67d6da
--- /dev/null
+++ b/docs/task-issues.md
@@ -0,0 +1,28 @@
+# C++ task related issues
+
+NB Comment | LWG Issue | State | Section | Title
+-----------|-----------|-------|---------|------
+[US 232-366](https://github.com/cplusplus/nbballot/issues/941) | [LWG4329](https://cplusplus.github.io/LWG/issue4329) [P3941](https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2026/p3941r1.html) | open/SG1 | [33.13.3](https://wg21.link/exec.affine.on) | Specify customizations for `affine_on` when sender does not change scheduler
+[US 233-365](https://github.com/cplusplus/nbballot/issues/940) | [LWG4330](https://cplusplus.github.io/LWG/issue4330) [P3941](https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2026/p3941r1.html) | open/SG1 | [33.13.3](https://wg21.link/exec.affine.on) | Clarify `affine_on` vs. `continues_on`
+[US 234-364](https://github.com/cplusplus/nbballot/issues/939) | [LWG4331](https://cplusplus.github.io/LWG/issue4331) [P3941](https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2026/p3941r1.html) | open/LEWG | [33.13.3](https://wg21.link/exec.affine.on) | Remove scheduler parameter from `affine_on`
+[US 235-363](https://github.com/cplusplus/nbballot/issues/938) | [LWG4332](https://cplusplus.github.io/LWG/issue4332) [P3941](https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2026/p3941r1.html) | open/SG1 | [33.13.3](https://wg21.link/exec.affine.on) | `affine_on` should not forward the stop token to the scheduling operation
+[US 236-362](https://github.com/cplusplus/nbballot/issues/937) | [LWG4344](https://cplusplus.github.io/LWG/issue4344) [P3941](https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2026/p3941r1.html) | open/SG1 | [33.13.3](https://wg21.link/exec.affine.on) | Specify default implementation of `affine_on`
+[US 237-369](https://github.com/cplusplus/nbballot/issues/944) | [LWG4342](https://cplusplus.github.io/LWG/issue4342) | closed | [33.13.5](https://wg21.link/exec.task.scheduler) | Add rvalue reference qualification to <code>task_scheduler::<i>ts-sender</i>::connect</code>
+[US 238-368](https://github.com/cplusplus/nbballot/issues/943) | [LWG4336](https://cplusplus.github.io/LWG/issue4336) [P3927](https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2026/p3927r0.html) | open/LEWG | [33.13.5](https://wg21.link/exec.task.scheduler) | Allow customizations when using `task_scheduler`
+[US 239-367](https://github.com/cplusplus/nbballot/issues/942) | | closed | [33.13.5](https://wg21.link/exec.task.scheduler) | <code><i>sch_</i></code> must not be in moved-from state
+[US 242-372](https://github.com/cplusplus/nbballot/issues/947) | [LWG4339](https://cplusplus.github.io/LWG/issue4339) | open/LWG | [33.13.6](https://wg21.link/exec.task) | Timing of destruction of coroutine frame
+[US 243-376](https://github.com/cplusplus/nbballot/issues/951) |  | closed | [33.13.6.2](https://wg21.link/task.class) | Add default template arguments for `task`
+[US 244-375](https://github.com/cplusplus/nbballot/issues/950) | [LWG4341](https://cplusplus.github.io/LWG/issue4341) | closed | [33.13.6.2](https://wg21.link/task.class) | Add rvalue reference qualifier for `task::connect()`
+[US 245-374](https://github.com/cplusplus/nbballot/issues/949) | [LWG4338](https://cplusplus.github.io/LWG/issue4338) | rejected | [33.13.6.2](https://wg21.link/task.class) | Add `operator co_await`
+[US 246-373](https://github.com/cplusplus/nbballot/issues/948) | [LWG4348](https://cplusplus.github.io/LWG/issue4348) | ⚠️open/SG1 | [33.13.6.2](https://wg21.link/task.class) | Support symmetric transfer
+[US 249-379](https://github.com/cplusplus/nbballot/issues/954) | | ⚠️open/LWG | [33.13.6.4p4](https://wg21.link/task.state#4) | Move specification for `stop_token_type`
+[US 250-389](https://github.com/cplusplus/nbballot/issues/964) | [LWG4346](https://cplusplus.github.io/LWG/issue4346) | closed | [33.13.6.5](https://wg21.link/task.promise) | Add specification for `return_void` and `return_value`
+[US 251-388](https://github.com/cplusplus/nbballot/issues/963) | [LWG4345](https://cplusplus.github.io/LWG/issue4345) | closed | [33.13.6.5](https://wg21.link/task.promise) | Add default template argument for `return_value`
+[US 252-387](https://github.com/cplusplus/nbballot/issues/962) | [LWG4340](https://cplusplus.github.io/LWG/issue4340) | closed | [33.13.6.5](https://wg21.link/task.promise) | `task::promise_type::unhandled_stopped()` should be `noexcept`
+[US 253-386](https://github.com/cplusplus/nbballot/issues/961) | [LWG4333](https://cplusplus.github.io/LWG/issue4333) | ⚠️open/LEWG | [33.13.6.5](https://wg21.link/task.promise) | Allow use of arbitrary allocators for coroutine frame
+[US 254-385](https://github.com/cplusplus/nbballot/issues/960) | [LWG4334](https://cplusplus.github.io/LWG/issue4334) | ⚠️open/LEWG | [33.13.6.5](https://wg21.link/task.promise) | Constraint `allocator_arg` argument to be the first argument
+[US 255-384](https://github.com/cplusplus/nbballot/issues/959) | [LWG4335](https://cplusplus.github.io/LWG/issue4335) | ⚠️open/LEWG | [33.13.6.5](https://wg21.link/task.promise) | Use allocator from receiver's environment 
+[US 256-383](https://github.com/cplusplus/nbballot/issues/958) | [LWG4337](https://cplusplus.github.io/LWG/issue4337) | rejected |  [33.13.6.5](https://wg21.link/task.promise) | Scheduler need not be assignable
+[US 257-382](https://github.com/cplusplus/nbballot/issues/957) | [LWG4347](https://cplusplus.github.io/LWG/issue4347) | ⚠️open/LWG | [33.13.6.5](https://wg21.link/task.promise) | Respecify source and token members
+[US 258-381](https://github.com/cplusplus/nbballot/issues/956) | [LWG4349](https://cplusplus.github.io/LWG/issue4349) | closed | [33.13.6.5](https://wg21.link/task.promise) | Clarify `task` is not eagerly started
+[US 261-391](https://github.com/cplusplus/nbballot/issues/966) | | ⚠️open/LEWG | [33.13.6.5](https://wg21.link/task.promise) [p3](https://wg21.link/task.promise#3), [p16](https://wg21.link/task.promise#16), [p17](https://wg21.link/task.promise#17) | Bad specification of parameter type
diff --git a/examples/issue-affine_on.cpp b/examples/issue-affine_on.cpp
index 2b9b709..45fbd9f 100644
--- a/examples/issue-affine_on.cpp
+++ b/examples/issue-affine_on.cpp
@@ -15,10 +15,8 @@ ex::task<> test(Sender&& sender) {
 int main() {
     ex::sync_wait(test(ex::just()));
     ex::sync_wait(test(ex::read_env(ex::get_scheduler)));
-#if 0
     ex::sync_wait(test(ex::read_env(ex::get_scheduler) |
                     ex::let_value([](auto sched) noexcept { return ex::just(); })));
     ex::sync_wait(test(ex::read_env(ex::get_scheduler) |
                        ex::let_value([](auto sched) { return ex::starts_on(sched, ex::just()); })));
-#endif
 }

From a87856f11ed01f4341f4a70ac70555dc78044e60 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Dietmar=20K=C3=BChl?= <dietmar.kuehl@me.com>
Date: Mon, 26 Jan 2026 20:58:31 +0000
Subject: [PATCH 02/12] updated the overview

---
 docs/task-issues.md | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/docs/task-issues.md b/docs/task-issues.md
index e67d6da..4bd3b74 100644
--- a/docs/task-issues.md
+++ b/docs/task-issues.md
@@ -19,10 +19,10 @@ NB Comment | LWG Issue | State | Section | Title
 [US 250-389](https://github.com/cplusplus/nbballot/issues/964) | [LWG4346](https://cplusplus.github.io/LWG/issue4346) | closed | [33.13.6.5](https://wg21.link/task.promise) | Add specification for `return_void` and `return_value`
 [US 251-388](https://github.com/cplusplus/nbballot/issues/963) | [LWG4345](https://cplusplus.github.io/LWG/issue4345) | closed | [33.13.6.5](https://wg21.link/task.promise) | Add default template argument for `return_value`
 [US 252-387](https://github.com/cplusplus/nbballot/issues/962) | [LWG4340](https://cplusplus.github.io/LWG/issue4340) | closed | [33.13.6.5](https://wg21.link/task.promise) | `task::promise_type::unhandled_stopped()` should be `noexcept`
-[US 253-386](https://github.com/cplusplus/nbballot/issues/961) | [LWG4333](https://cplusplus.github.io/LWG/issue4333) | ⚠️open/LEWG | [33.13.6.5](https://wg21.link/task.promise) | Allow use of arbitrary allocators for coroutine frame
-[US 254-385](https://github.com/cplusplus/nbballot/issues/960) | [LWG4334](https://cplusplus.github.io/LWG/issue4334) | ⚠️open/LEWG | [33.13.6.5](https://wg21.link/task.promise) | Constraint `allocator_arg` argument to be the first argument
-[US 255-384](https://github.com/cplusplus/nbballot/issues/959) | [LWG4335](https://cplusplus.github.io/LWG/issue4335) | ⚠️open/LEWG | [33.13.6.5](https://wg21.link/task.promise) | Use allocator from receiver's environment 
+[US 253-386](https://github.com/cplusplus/nbballot/issues/961) | [LWG4333](https://cplusplus.github.io/LWG/issue4333) [D3980](https://isocpp.org/files/papers/D3980R0.html) | ✓open/LEWG | [33.13.6.5](https://wg21.link/task.promise) | Allow use of arbitrary allocators for coroutine frame
+[US 254-385](https://github.com/cplusplus/nbballot/issues/960) | [LWG4334](https://cplusplus.github.io/LWG/issue4334) [D3980](https://isocpp.org/files/papers/D3980R0.html) | ✓open/LEWG | [33.13.6.5](https://wg21.link/task.promise) | Constraint `allocator_arg` argument to be the first argument
+[US 255-384](https://github.com/cplusplus/nbballot/issues/959) | [LWG4335](https://cplusplus.github.io/LWG/issue4335) [D3980](https://isocpp.org/files/papers/D3980R0.html) | ✓open/LEWG | [33.13.6.5](https://wg21.link/task.promise) | Use allocator from receiver's environment 
 [US 256-383](https://github.com/cplusplus/nbballot/issues/958) | [LWG4337](https://cplusplus.github.io/LWG/issue4337) | rejected |  [33.13.6.5](https://wg21.link/task.promise) | Scheduler need not be assignable
 [US 257-382](https://github.com/cplusplus/nbballot/issues/957) | [LWG4347](https://cplusplus.github.io/LWG/issue4347) | ⚠️open/LWG | [33.13.6.5](https://wg21.link/task.promise) | Respecify source and token members
 [US 258-381](https://github.com/cplusplus/nbballot/issues/956) | [LWG4349](https://cplusplus.github.io/LWG/issue4349) | closed | [33.13.6.5](https://wg21.link/task.promise) | Clarify `task` is not eagerly started
-[US 261-391](https://github.com/cplusplus/nbballot/issues/966) | | ⚠️open/LEWG | [33.13.6.5](https://wg21.link/task.promise) [p3](https://wg21.link/task.promise#3), [p16](https://wg21.link/task.promise#16), [p17](https://wg21.link/task.promise#17) | Bad specification of parameter type
+[US 261-391](https://github.com/cplusplus/nbballot/issues/966) | [D3980](https://isocpp.org/files/papers/D3980R0.html) | ✓open/LEWG | [33.13.6.5](https://wg21.link/task.promise) [p3](https://wg21.link/task.promise#3), [p16](https://wg21.link/task.promise#16), [p17](https://wg21.link/task.promise#17) | Bad specification of parameter type

From daacb3749b9710ad5f1078af9fd8c157fdbbfe8a Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Dietmar=20K=C3=BChl?= <dietmar.kuehl@me.com>
Date: Wed, 18 Feb 2026 21:08:04 +0000
Subject: [PATCH 03/12] added the missing member operator new

---
 docs/P3980-allocation.md | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/docs/P3980-allocation.md b/docs/P3980-allocation.md
index b0b21cf..ada2abf 100644
--- a/docs/P3980-allocation.md
+++ b/docs/P3980-allocation.md
@@ -187,6 +187,8 @@ namespace std::execution {
     @[void*]{.add}@ @[operator]{.add}@ @[new(size_t]{.add}@ @[size);]{.add}@
     template<@[class Alloc,]{.add}@ class... Args>
       void* operator new(size_t size, @[allocator_arg_t,]{.add}@ @[Alloc]{.add}@ @[alloc, ]{.add}@Args&&... @[args]{.rm}@);
+    @[template<class]{.add}@ @[This,]{.add}@ @[class]{.add}@ @[Alloc,]{.add}@ @[class ...]{.add}@ @[Args>]{.add}@
+      @[void*]{.add}@ @[operator]{.add}@ @[new(size_t]{.add}@ @[size,]{.add}@ @[const]{.add}@ @[This&,]{.add}@ @[allocator_arg_t,]{.add}@ @[Alloc]{.add}@ @[alloc,]{.add}@ @[Args&&...);]{.add}@
 
     void operator delete(void* pointer, size_t size) noexcept;
 
@@ -213,6 +215,8 @@ void* operator new(size_t size);
 ```
 template<@[class Alloc,]{.add}@ class... Args>
   void* operator new(size_t size, @[allocator_arg_t,]{.add}@ @[Alloc]{.add}@ @[alloc, ]{.add}@Args&&... @[args]{.rm}@);
+@[template<class]{.add}@ @[This,]{.add}@ @[class]{.add}@ @[Alloc,]{.add}@ @[class ...]{.add}@ @[Args>]{.add}@
+  @[void*]{.add}@ @[operator]{.add}@ @[new(size_t]{.add}@ @[size,]{.add}@ @[const]{.add}@ @[This&,]{.add}@ @[allocator_arg_t,]{.add}@ @[Alloc]{.add}@ @[alloc,]{.add}@ @[Args&&...);]{.add}@
 ```
 
 [17]{.pnum} [If there is no parameter with type `allocator_arg_t`

From 1930e4d1b96109c7c26b9ea102d2bef83c6ebc20 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Dietmar=20K=C3=BChl?= <dietmar.kuehl@me.com>
Date: Sun, 22 Feb 2026 19:14:42 +0000
Subject: [PATCH 04/12] fix date and typos

---
 docs/P3980-allocation.md | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/docs/P3980-allocation.md b/docs/P3980-allocation.md
index ada2abf..d518e4b 100644
--- a/docs/P3980-allocation.md
+++ b/docs/P3980-allocation.md
@@ -1,7 +1,7 @@
 ---
 title: Task's Allocator Use
 document: D3980R0
-date: 2026-01-25
+date: 2026-02-22
 audience:
     - Library Evolution Working Group (LEWG)
     - Library Working Group (LWG)
@@ -52,9 +52,9 @@ The first issue
 ([US 254-385](https://github.com/cplusplus/nbballot/issues/960)) is
 about where an allocator argument for the coroutine frame may go
 on the coroutine function.  The options are a fixed location (which
-would first for consistency with existing use) and anywhere. The
-status quo is anywhere and the request is to require that it goes
-first. However, to support optionally passing an allocator having
+would fit first for consistency with existing use) and anywhere. The
+status quo is anywhere, and the request is to require that it goes
+first. However, to support optionally passing an allocator, having
 it go anywhere is easier to do.
 </p>
 <p>
@@ -70,7 +70,7 @@ and the third
 ([US 255-384](https://github.com/cplusplus/nbballot/issues/959)) issues.
 </p>
 <p>
-The forth issue ([US
+The fourth issue ([US
 261-391](https://github.com/cplusplus/nbballot/issues/966)) is
 primarily a wording issue. However, some of the problematic paragraphs
 will need some modifications to address the other issues, i.e., fixing

From dbdf2c0223ff4b66f4911b25daf366080e161c5b Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Dietmar=20K=C3=BChl?= <dietmar.kuehl@me.com>
Date: Sun, 22 Feb 2026 20:12:26 +0000
Subject: [PATCH 05/12] fixed a few issues, brought date up to date, and add
 LEWG outcome

---
 docs/P3980-allocation.md | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/docs/P3980-allocation.md b/docs/P3980-allocation.md
index d518e4b..fbb3230 100644
--- a/docs/P3980-allocation.md
+++ b/docs/P3980-allocation.md
@@ -169,6 +169,9 @@ Below are three variations of the wording changes, only one can be picked:
 <li>Flexible position of the allocator arg and use the receiver's allocator for the environment.</li>
 </ol>
 
+At the LEWG meeting on 2026-02-03 the first approach (putting the `allocator_arg` first, Wording Change A)
+was preferred ([notes](https://wiki.isocpp.org/2026-02-03_LEWG_Telecon)). It was identified that the original wording change did not support member functions returning a `task` (the wording was fixed accordingly).
+
 ## Wording Change A: `allocator_arg` must be first argument
 
 ::: ednote

From 31c2b475d0e787eac5cae4bb7792be435128faac Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Dietmar=20K=C3=BChl?= <dietmar.kuehl@me.com>
Date: Tue, 24 Feb 2026 00:27:51 +0000
Subject: [PATCH 06/12] fix some typos and update the execution reference

---
 CMakeLists.txt           | 2 +-
 docs/P3980-allocation.md | 8 ++++----
 2 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/CMakeLists.txt b/CMakeLists.txt
index c6034d8..23158af 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -30,7 +30,7 @@ FetchContent_Declare(
     execution
     # SOURCE_DIR ${CMAKE_SOURCE_DIR}/../execution
     GIT_REPOSITORY https://github.com/bemanproject/execution
-    GIT_TAG 66295d5
+    GIT_TAG 3650634
     SYSTEM
     FIND_PACKAGE_ARGS
         0.2.0
diff --git a/docs/P3980-allocation.md b/docs/P3980-allocation.md
index fbb3230..199882e 100644
--- a/docs/P3980-allocation.md
+++ b/docs/P3980-allocation.md
@@ -156,7 +156,7 @@ a coroutine function may want to support:
   <li>Mandate that the allocator is the first argument (`comes_first`): the use is identical.</li>
   <li>
     Support optionally passing an `allocator_arg`/allocator pair
-    (`optional`): the use can be identical but it can also be simplied
+    (`optional`): the use can be identical but it can also be simplifed
     taking advantage of the flexible location.
   </li>
 </ol>
@@ -263,7 +263,7 @@ with an allocator equal to `palloc`.
 
 ::: ednote
 
-Change [task.promise] pargraph 17 and 18 to use the correct type:
+Change [task.promise] paragraph 17 and 18 to use the correct type:
 
 :::
 
@@ -302,7 +302,7 @@ with an allocator equal to `palloc`.
 
 ::: ednote
 
-Change [task.promise] pargraph 17 and 18 to use the correct type and don't convert to `allocator_type`:
+Change [task.promise] paragraph 17 and 18 to use the correct type and don't convert to `allocator_type`:
 
 :::
 
@@ -454,7 +454,7 @@ with the corresponding next element of `args`. Otherwise,
 ::: ednote
 
 Change `get_env` to get the allocator from the receiver when needed
-in [[task.promise] p16](https://wg21.link/task.pomise#16):
+in [[task.promise] p16](https://wg21.link/task.promise#16):
 
 :::
 

From ab16c4a9f613ce4dfd0074ff1f0dc3833314045a Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Dietmar=20K=C3=BChl?= <dietmar.kuehl@me.com>
Date: Tue, 24 Feb 2026 01:17:58 +0000
Subject: [PATCH 07/12] fixing a few more CI issues

---
 docs/P3980-allocation.md     | 4 ++--
 docs/task-issues.md          | 2 +-
 examples/issue-affine_on.cpp | 3 +--
 3 files changed, 4 insertions(+), 5 deletions(-)

diff --git a/docs/P3980-allocation.md b/docs/P3980-allocation.md
index 199882e..ee6279a 100644
--- a/docs/P3980-allocation.md
+++ b/docs/P3980-allocation.md
@@ -156,7 +156,7 @@ a coroutine function may want to support:
   <li>Mandate that the allocator is the first argument (`comes_first`): the use is identical.</li>
   <li>
     Support optionally passing an `allocator_arg`/allocator pair
-    (`optional`): the use can be identical but it can also be simplifed
+    (`optional`): the use can be identical but it can also be simplified
     taking advantage of the flexible location.
   </li>
 </ol>
@@ -361,7 +361,7 @@ be the result of `get_env(rcvr)`. The implication is that the `task`'s
     Otherwise `allocator_type(get_allocator(ev))` has to be well-formed.
   </li>
   <li>
-    There is no need to store an <code><i>alloc</i></code> in the 
+    There is no need to store an <code><i>alloc</i></code> in the
     `promise_type`: it can be obtained when requested from `ev` which,
     in turn, can be obtained from `rcvr`. Thus, the ctor for `promise_type`
     isn't needed.
diff --git a/docs/task-issues.md b/docs/task-issues.md
index 4bd3b74..9da8013 100644
--- a/docs/task-issues.md
+++ b/docs/task-issues.md
@@ -21,7 +21,7 @@ NB Comment | LWG Issue | State | Section | Title
 [US 252-387](https://github.com/cplusplus/nbballot/issues/962) | [LWG4340](https://cplusplus.github.io/LWG/issue4340) | closed | [33.13.6.5](https://wg21.link/task.promise) | `task::promise_type::unhandled_stopped()` should be `noexcept`
 [US 253-386](https://github.com/cplusplus/nbballot/issues/961) | [LWG4333](https://cplusplus.github.io/LWG/issue4333) [D3980](https://isocpp.org/files/papers/D3980R0.html) | ✓open/LEWG | [33.13.6.5](https://wg21.link/task.promise) | Allow use of arbitrary allocators for coroutine frame
 [US 254-385](https://github.com/cplusplus/nbballot/issues/960) | [LWG4334](https://cplusplus.github.io/LWG/issue4334) [D3980](https://isocpp.org/files/papers/D3980R0.html) | ✓open/LEWG | [33.13.6.5](https://wg21.link/task.promise) | Constraint `allocator_arg` argument to be the first argument
-[US 255-384](https://github.com/cplusplus/nbballot/issues/959) | [LWG4335](https://cplusplus.github.io/LWG/issue4335) [D3980](https://isocpp.org/files/papers/D3980R0.html) | ✓open/LEWG | [33.13.6.5](https://wg21.link/task.promise) | Use allocator from receiver's environment 
+[US 255-384](https://github.com/cplusplus/nbballot/issues/959) | [LWG4335](https://cplusplus.github.io/LWG/issue4335) [D3980](https://isocpp.org/files/papers/D3980R0.html) | ✓open/LEWG | [33.13.6.5](https://wg21.link/task.promise) | Use allocator from receiver's environment
 [US 256-383](https://github.com/cplusplus/nbballot/issues/958) | [LWG4337](https://cplusplus.github.io/LWG/issue4337) | rejected |  [33.13.6.5](https://wg21.link/task.promise) | Scheduler need not be assignable
 [US 257-382](https://github.com/cplusplus/nbballot/issues/957) | [LWG4347](https://cplusplus.github.io/LWG/issue4347) | ⚠️open/LWG | [33.13.6.5](https://wg21.link/task.promise) | Respecify source and token members
 [US 258-381](https://github.com/cplusplus/nbballot/issues/956) | [LWG4349](https://cplusplus.github.io/LWG/issue4349) | closed | [33.13.6.5](https://wg21.link/task.promise) | Clarify `task` is not eagerly started
diff --git a/examples/issue-affine_on.cpp b/examples/issue-affine_on.cpp
index 45fbd9f..b5894dd 100644
--- a/examples/issue-affine_on.cpp
+++ b/examples/issue-affine_on.cpp
@@ -15,8 +15,7 @@ ex::task<> test(Sender&& sender) {
 int main() {
     ex::sync_wait(test(ex::just()));
     ex::sync_wait(test(ex::read_env(ex::get_scheduler)));
-    ex::sync_wait(test(ex::read_env(ex::get_scheduler) |
-                    ex::let_value([](auto sched) noexcept { return ex::just(); })));
+    ex::sync_wait(test(ex::read_env(ex::get_scheduler) | ex::let_value([](auto) noexcept { return ex::just(); })));
     ex::sync_wait(test(ex::read_env(ex::get_scheduler) |
                        ex::let_value([](auto sched) { return ex::starts_on(sched, ex::just()); })));
 }

From 520072ed6e09db012927e949f5b2b9efedb8cbb8 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Dietmar=20K=C3=BChl?= <dietmar.kuehl@me.com>
Date: Mon, 23 Mar 2026 02:48:25 +0000
Subject: [PATCH 08/12] changed the code to take the allocator from the
 environment

---
 include/beman/task/detail/awaiter.hpp      | 7 +++++++
 include/beman/task/detail/promise_type.hpp | 6 +-----
 include/beman/task/detail/state.hpp        | 7 +++++++
 include/beman/task/detail/state_base.hpp   | 4 ++++
 tests/beman/task/promise_base.test.cpp     | 3 +++
 tests/beman/task/promise_type.test.cpp     | 3 +++
 tests/beman/task/state_base.test.cpp       | 3 +++
 7 files changed, 28 insertions(+), 5 deletions(-)

diff --git a/include/beman/task/detail/awaiter.hpp b/include/beman/task/detail/awaiter.hpp
index 4eff758..1bf1edb 100644
--- a/include/beman/task/detail/awaiter.hpp
+++ b/include/beman/task/detail/awaiter.hpp
@@ -48,6 +48,7 @@ struct awaiter_op_t<Awaiter, ParentPromise, false> {
 template <typename Value, typename Env, typename OwnPromise, typename ParentPromise>
 class awaiter : public ::beman::task::detail::state_base<Value, Env> {
   public:
+    using allocator_type = typename ::beman::task::detail::state_base<Value, Env>::allocator_type;
     using stop_token_type = typename ::beman::task::detail::state_base<Value, Env>::stop_token_type;
     using scheduler_type  = typename ::beman::task::detail::state_base<Value, Env>::scheduler_type;
 
@@ -87,6 +88,12 @@ class awaiter : public ::beman::task::detail::state_base<Value, Env> {
     auto actual_complete() -> std::coroutine_handle<> {
         return this->no_completion_set() ? this->parent.promise().unhandled_stopped() : ::std::move(this->parent);
     }
+    auto do_get_allocator() -> allocator_type override {
+        if constexpr (requires{ ::beman::execution::get_allocator(::beman::execution::get_env(this->parent)); })
+            return ::beman::execution::get_allocator(::beman::execution::get_env(this->parent));
+        else
+            return allocator_type{};
+    }
     auto do_get_scheduler() -> scheduler_type override { return *this->scheduler; }
     auto do_set_scheduler(scheduler_type other) -> scheduler_type override {
         return ::std::exchange(*this->scheduler, other);
diff --git a/include/beman/task/detail/promise_type.hpp b/include/beman/task/detail/promise_type.hpp
index 27467a9..0c2f60d 100644
--- a/include/beman/task/detail/promise_type.hpp
+++ b/include/beman/task/detail/promise_type.hpp
@@ -50,9 +50,6 @@ class promise_type
     using stop_source_type = ::beman::task::detail::stop_source_of_t<Environment>;
     using stop_token_type  = decltype(std::declval<stop_source_type>().get_token());
 
-    template <typename... A>
-    promise_type(const A&... a) : allocator(::beman::task::detail::find_allocator<allocator_type>(a...)) {}
-
     constexpr auto initial_suspend() noexcept -> ::std::suspend_always { return {}; }
     constexpr auto final_suspend() noexcept -> ::beman::task::detail::final_awaiter { return {}; }
 
@@ -106,7 +103,7 @@ class promise_type
     }
 
     auto get_scheduler() const noexcept -> scheduler_type { return this->get_state()->get_scheduler(); }
-    auto get_allocator() const noexcept -> allocator_type { return this->allocator; }
+    auto get_allocator() const noexcept -> allocator_type { return this->get_state()->get_allocator(); }
     auto get_stop_token() const noexcept -> stop_token_type { return this->get_state()->get_stop_token(); }
     auto get_environment() const noexcept -> const Environment& {
         assert(this);
@@ -117,7 +114,6 @@ class promise_type
   private:
     using env_t = ::beman::task::detail::promise_env<promise_type>;
 
-    allocator_type                  allocator{};
     ::std::optional<scheduler_type> scheduler{};
 };
 } // namespace beman::task::detail
diff --git a/include/beman/task/detail/state.hpp b/include/beman/task/detail/state.hpp
index 714a077..10ff50c 100644
--- a/include/beman/task/detail/state.hpp
+++ b/include/beman/task/detail/state.hpp
@@ -20,6 +20,7 @@ struct state : ::beman::task::detail::state_base<T, C>, ::beman::task::detail::s
     using operation_state_concept = ::beman::execution::operation_state_t;
     using promise_type            = ::beman::task::detail::promise_type<Task, T, C>;
     using scheduler_type          = typename ::beman::task::detail::state_base<T, C>::scheduler_type;
+    using allocator_type          = typename ::beman::task::detail::state_base<T, C>::allocator_type;
     using stop_source_type        = ::beman::task::detail::stop_source_of_t<C>;
     using stop_token_type         = decltype(std::declval<stop_source_type>().get_token());
     using stop_token_t =
@@ -46,6 +47,12 @@ struct state : ::beman::task::detail::state_base<T, C>, ::beman::task::detail::s
         this->result_complete(::std::move(this->receiver));
         return std::noop_coroutine();
     }
+    auto do_get_allocator() -> allocator_type override {
+        if constexpr (requires{ ::beman::execution::get_allocator(this->receiver); })
+            return ::beman::execution::get_allocator(this->receiver);
+        else
+            return allocator_type{};
+    }
     auto do_get_scheduler() -> scheduler_type override { return this->scheduler; }
     auto do_set_scheduler(scheduler_type other) -> scheduler_type override {
         return ::std::exchange(this->scheduler, other);
diff --git a/include/beman/task/detail/state_base.hpp b/include/beman/task/detail/state_base.hpp
index 53c7096..e9c4765 100644
--- a/include/beman/task/detail/state_base.hpp
+++ b/include/beman/task/detail/state_base.hpp
@@ -6,6 +6,7 @@
 
 #include <beman/task/detail/stop_source.hpp>
 #include <beman/task/detail/scheduler_of.hpp>
+#include <beman/task/detail/allocator_of.hpp>
 #include <beman/task/detail/error_types_of.hpp>
 #include <beman/task/detail/result_type.hpp>
 #include <coroutine>
@@ -18,11 +19,13 @@ class state_base : public ::beman::task::detail::result_type<::beman::task::deta
                                                              Value,
                                                              ::beman::task::detail::error_types_of_t<Environment>> {
   public:
+    using allocator_type = ::beman::task::detail::allocator_of_t<Environment>;
     using stop_source_type = ::beman::task::detail::stop_source_of_t<Environment>;
     using stop_token_type  = decltype(std::declval<stop_source_type>().get_token());
     using scheduler_type   = ::beman::task::detail::scheduler_of_t<Environment>;
 
     auto complete() -> std::coroutine_handle<> { return this->do_complete(); }
+    auto get_allocator() -> allocator_type { return this->do_get_allocator(); }
     auto get_stop_token() -> stop_token_type { return this->do_get_stop_token(); }
     auto get_environment() -> Environment& {
         assert(this);
@@ -43,6 +46,7 @@ class state_base : public ::beman::task::detail::result_type<::beman::task::deta
 
     // NOLINTBEGIN(portability-template-virtual-member-function)
     virtual auto do_complete() -> std::coroutine_handle<>                 = 0;
+    virtual auto do_get_allocator() -> allocator_type                     = 0;
     virtual auto do_get_stop_token() -> stop_token_type                   = 0;
     virtual auto do_get_environment() -> Environment&                     = 0;
     virtual auto do_get_scheduler() -> scheduler_type                     = 0;
diff --git a/tests/beman/task/promise_base.test.cpp b/tests/beman/task/promise_base.test.cpp
index 77a7535..1ac9b13 100644
--- a/tests/beman/task/promise_base.test.cpp
+++ b/tests/beman/task/promise_base.test.cpp
@@ -2,6 +2,7 @@
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
 #include <beman/task/detail/promise_base.hpp>
+#include <beman/task/detail/allocator_of.hpp>
 #include <beman/task/detail/state_base.hpp>
 #include <beman/task/detail/inline_scheduler.hpp>
 #include <beman/execution/execution.hpp>
@@ -48,6 +49,7 @@ struct env {
 template <typename T, typename... E>
 struct state : bt::state_base<T, env<E...>> {
     using Environment      = env<E...>;
+    using allocator_type   = ::beman::task::detail::allocator_of_t<Environment>;
     using stop_source_type = ::beman::task::detail::stop_source_of_t<Environment>;
     using stop_token_type  = decltype(std::declval<stop_source_type>().get_token());
     using scheduler_type   = ::beman::task::detail::scheduler_of_t<Environment>;
@@ -62,6 +64,7 @@ struct state : bt::state_base<T, env<E...>> {
         this->completed = true;
         return std::noop_coroutine();
     }
+    allocator_type do_get_allocator() override { return allocator_type{}; }
     stop_token_type do_get_stop_token() override {
         this->token = true;
         return this->source.get_token();
diff --git a/tests/beman/task/promise_type.test.cpp b/tests/beman/task/promise_type.test.cpp
index a6c002b..76beaa3 100644
--- a/tests/beman/task/promise_type.test.cpp
+++ b/tests/beman/task/promise_type.test.cpp
@@ -2,6 +2,7 @@
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
 #include <beman/task/detail/promise_type.hpp>
+#include <beman/task/detail/allocator_of.hpp>
 #include <beman/task/detail/task_scheduler.hpp>
 #include <beman/task/detail/inline_scheduler.hpp>
 #include <beman/execution/execution.hpp>
@@ -129,6 +130,7 @@ struct test_error : std::exception {
 struct test_task : beman::task::detail::state_base<int, environment> {
 
     using promise_type = beman::task::detail::promise_type<test_task, int, environment>;
+    using allocator_type   = ::beman::task::detail::allocator_of_t<environment>;
 
     beman::task::detail::handle<promise_type> handle;
     explicit test_task(beman::task::detail::handle<promise_type> h) : handle(std::move(h)) {}
@@ -153,6 +155,7 @@ struct test_task : beman::task::detail::state_base<int, environment> {
         this->latch.count_down();
         return std::noop_coroutine();
     }
+    allocator_type do_get_allocator() override { return allocator_type{}; }
     stop_token_type do_get_stop_token() override { return this->source.get_token(); }
     environment&    do_get_environment() override { return this->env; }
     auto            do_get_scheduler() -> scheduler_type override { return scheduler_type(bt::inline_scheduler()); }
diff --git a/tests/beman/task/state_base.test.cpp b/tests/beman/task/state_base.test.cpp
index eae9623..02a16e0 100644
--- a/tests/beman/task/state_base.test.cpp
+++ b/tests/beman/task/state_base.test.cpp
@@ -3,6 +3,7 @@
 
 #include <beman/task/detail/state_base.hpp>
 #include <beman/task/detail/inline_scheduler.hpp>
+#include <beman/task/detail/allocator_of.hpp>
 #ifdef NDEBUG
 #undef NDEBUG
 #endif
@@ -16,6 +17,7 @@ namespace {
 struct environment {};
 
 struct state : beman::task::detail::state_base<int, environment> {
+    using allocator_type   = ::beman::task::detail::allocator_of_t<environment>;
     stop_source_type source;
     environment      env;
     bool             completed{};
@@ -26,6 +28,7 @@ struct state : beman::task::detail::state_base<int, environment> {
         this->completed = true;
         return std::noop_coroutine();
     }
+    allocator_type do_get_allocator() override { return allocator_type{}; }
     stop_token_type do_get_stop_token() override {
         this->token = true;
         return this->source.get_token();

From 1bab4fb14b4fa440950a54b1c238387e57118429 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Dietmar=20K=C3=BChl?= <dietmar.kuehl@me.com>
Date: Mon, 23 Mar 2026 02:49:42 +0000
Subject: [PATCH 09/12] clang-format

---
 include/beman/task/detail/awaiter.hpp    | 4 ++--
 include/beman/task/detail/state.hpp      | 2 +-
 include/beman/task/detail/state_base.hpp | 2 +-
 tests/beman/task/promise_base.test.cpp   | 2 +-
 tests/beman/task/promise_type.test.cpp   | 4 ++--
 tests/beman/task/state_base.test.cpp     | 4 ++--
 6 files changed, 9 insertions(+), 9 deletions(-)

diff --git a/include/beman/task/detail/awaiter.hpp b/include/beman/task/detail/awaiter.hpp
index 1bf1edb..2225c5d 100644
--- a/include/beman/task/detail/awaiter.hpp
+++ b/include/beman/task/detail/awaiter.hpp
@@ -48,7 +48,7 @@ struct awaiter_op_t<Awaiter, ParentPromise, false> {
 template <typename Value, typename Env, typename OwnPromise, typename ParentPromise>
 class awaiter : public ::beman::task::detail::state_base<Value, Env> {
   public:
-    using allocator_type = typename ::beman::task::detail::state_base<Value, Env>::allocator_type;
+    using allocator_type  = typename ::beman::task::detail::state_base<Value, Env>::allocator_type;
     using stop_token_type = typename ::beman::task::detail::state_base<Value, Env>::stop_token_type;
     using scheduler_type  = typename ::beman::task::detail::state_base<Value, Env>::scheduler_type;
 
@@ -89,7 +89,7 @@ class awaiter : public ::beman::task::detail::state_base<Value, Env> {
         return this->no_completion_set() ? this->parent.promise().unhandled_stopped() : ::std::move(this->parent);
     }
     auto do_get_allocator() -> allocator_type override {
-        if constexpr (requires{ ::beman::execution::get_allocator(::beman::execution::get_env(this->parent)); })
+        if constexpr (requires { ::beman::execution::get_allocator(::beman::execution::get_env(this->parent)); })
             return ::beman::execution::get_allocator(::beman::execution::get_env(this->parent));
         else
             return allocator_type{};
diff --git a/include/beman/task/detail/state.hpp b/include/beman/task/detail/state.hpp
index 10ff50c..9825a23 100644
--- a/include/beman/task/detail/state.hpp
+++ b/include/beman/task/detail/state.hpp
@@ -48,7 +48,7 @@ struct state : ::beman::task::detail::state_base<T, C>, ::beman::task::detail::s
         return std::noop_coroutine();
     }
     auto do_get_allocator() -> allocator_type override {
-        if constexpr (requires{ ::beman::execution::get_allocator(this->receiver); })
+        if constexpr (requires { ::beman::execution::get_allocator(this->receiver); })
             return ::beman::execution::get_allocator(this->receiver);
         else
             return allocator_type{};
diff --git a/include/beman/task/detail/state_base.hpp b/include/beman/task/detail/state_base.hpp
index e9c4765..6a43b42 100644
--- a/include/beman/task/detail/state_base.hpp
+++ b/include/beman/task/detail/state_base.hpp
@@ -19,7 +19,7 @@ class state_base : public ::beman::task::detail::result_type<::beman::task::deta
                                                              Value,
                                                              ::beman::task::detail::error_types_of_t<Environment>> {
   public:
-    using allocator_type = ::beman::task::detail::allocator_of_t<Environment>;
+    using allocator_type   = ::beman::task::detail::allocator_of_t<Environment>;
     using stop_source_type = ::beman::task::detail::stop_source_of_t<Environment>;
     using stop_token_type  = decltype(std::declval<stop_source_type>().get_token());
     using scheduler_type   = ::beman::task::detail::scheduler_of_t<Environment>;
diff --git a/tests/beman/task/promise_base.test.cpp b/tests/beman/task/promise_base.test.cpp
index 1ac9b13..7e4e00b 100644
--- a/tests/beman/task/promise_base.test.cpp
+++ b/tests/beman/task/promise_base.test.cpp
@@ -64,7 +64,7 @@ struct state : bt::state_base<T, env<E...>> {
         this->completed = true;
         return std::noop_coroutine();
     }
-    allocator_type do_get_allocator() override { return allocator_type{}; }
+    allocator_type  do_get_allocator() override { return allocator_type{}; }
     stop_token_type do_get_stop_token() override {
         this->token = true;
         return this->source.get_token();
diff --git a/tests/beman/task/promise_type.test.cpp b/tests/beman/task/promise_type.test.cpp
index 76beaa3..228a6a7 100644
--- a/tests/beman/task/promise_type.test.cpp
+++ b/tests/beman/task/promise_type.test.cpp
@@ -130,7 +130,7 @@ struct test_error : std::exception {
 struct test_task : beman::task::detail::state_base<int, environment> {
 
     using promise_type = beman::task::detail::promise_type<test_task, int, environment>;
-    using allocator_type   = ::beman::task::detail::allocator_of_t<environment>;
+    using allocator_type = ::beman::task::detail::allocator_of_t<environment>;
 
     beman::task::detail::handle<promise_type> handle;
     explicit test_task(beman::task::detail::handle<promise_type> h) : handle(std::move(h)) {}
@@ -155,7 +155,7 @@ struct test_task : beman::task::detail::state_base<int, environment> {
         this->latch.count_down();
         return std::noop_coroutine();
     }
-    allocator_type do_get_allocator() override { return allocator_type{}; }
+    allocator_type  do_get_allocator() override { return allocator_type{}; }
     stop_token_type do_get_stop_token() override { return this->source.get_token(); }
     environment&    do_get_environment() override { return this->env; }
     auto            do_get_scheduler() -> scheduler_type override { return scheduler_type(bt::inline_scheduler()); }
diff --git a/tests/beman/task/state_base.test.cpp b/tests/beman/task/state_base.test.cpp
index 02a16e0..5f24109 100644
--- a/tests/beman/task/state_base.test.cpp
+++ b/tests/beman/task/state_base.test.cpp
@@ -17,7 +17,7 @@ namespace {
 struct environment {};
 
 struct state : beman::task::detail::state_base<int, environment> {
-    using allocator_type   = ::beman::task::detail::allocator_of_t<environment>;
+    using allocator_type = ::beman::task::detail::allocator_of_t<environment>;
     stop_source_type source;
     environment      env;
     bool             completed{};
@@ -28,7 +28,7 @@ struct state : beman::task::detail::state_base<int, environment> {
         this->completed = true;
         return std::noop_coroutine();
     }
-    allocator_type do_get_allocator() override { return allocator_type{}; }
+    allocator_type  do_get_allocator() override { return allocator_type{}; }
     stop_token_type do_get_stop_token() override {
         this->token = true;
         return this->source.get_token();

From a67dd565f8453f571ca43077d11565e011bbc582 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Dietmar=20K=C3=BChl?= <dietmar.kuehl@me.com>
Date: Mon, 23 Mar 2026 02:52:02 +0000
Subject: [PATCH 10/12] fix formatting issue

---
 tests/beman/task/promise_type.test.cpp | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tests/beman/task/promise_type.test.cpp b/tests/beman/task/promise_type.test.cpp
index 228a6a7..eb8dc86 100644
--- a/tests/beman/task/promise_type.test.cpp
+++ b/tests/beman/task/promise_type.test.cpp
@@ -129,7 +129,7 @@ struct test_error : std::exception {
 
 struct test_task : beman::task::detail::state_base<int, environment> {
 
-    using promise_type = beman::task::detail::promise_type<test_task, int, environment>;
+    using promise_type   = ::beman::task::detail::promise_type<test_task, int, environment>;
     using allocator_type = ::beman::task::detail::allocator_of_t<environment>;
 
     beman::task::detail::handle<promise_type> handle;

From 89dd18e486fc842eb37e27fb37b624cd363c12e8 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Dietmar=20K=C3=BChl?= <dietmar.kuehl@me.com>
Date: Mon, 23 Mar 2026 02:59:02 +0000
Subject: [PATCH 11/12] fixed environment access in get_allocator

---
 include/beman/task/detail/awaiter.hpp | 4 ++--
 include/beman/task/detail/state.hpp   | 4 ++--
 2 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/include/beman/task/detail/awaiter.hpp b/include/beman/task/detail/awaiter.hpp
index 2225c5d..2fbef7e 100644
--- a/include/beman/task/detail/awaiter.hpp
+++ b/include/beman/task/detail/awaiter.hpp
@@ -89,8 +89,8 @@ class awaiter : public ::beman::task::detail::state_base<Value, Env> {
         return this->no_completion_set() ? this->parent.promise().unhandled_stopped() : ::std::move(this->parent);
     }
     auto do_get_allocator() -> allocator_type override {
-        if constexpr (requires { ::beman::execution::get_allocator(::beman::execution::get_env(this->parent)); })
-            return ::beman::execution::get_allocator(::beman::execution::get_env(this->parent));
+        if constexpr (requires { ::beman::execution::get_allocator(::beman::execution::get_env(this->parent.promise())); })
+            return ::beman::execution::get_allocator(::beman::execution::get_env(this->parent.promise()));
         else
             return allocator_type{};
     }
diff --git a/include/beman/task/detail/state.hpp b/include/beman/task/detail/state.hpp
index 9825a23..567fac0 100644
--- a/include/beman/task/detail/state.hpp
+++ b/include/beman/task/detail/state.hpp
@@ -48,8 +48,8 @@ struct state : ::beman::task::detail::state_base<T, C>, ::beman::task::detail::s
         return std::noop_coroutine();
     }
     auto do_get_allocator() -> allocator_type override {
-        if constexpr (requires { ::beman::execution::get_allocator(this->receiver); })
-            return ::beman::execution::get_allocator(this->receiver);
+        if constexpr (requires { ::beman::execution::get_allocator(::beman::execution::get_env(this->receiver)); })
+            return ::beman::execution::get_allocator(::beman::execution::get_env(this->receiver));
         else
             return allocator_type{};
     }

From e657f74be038f97b6d0d379fa1330e22c4e17adf Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Dietmar=20K=C3=BChl?= <dietmar.kuehl@me.com>
Date: Mon, 23 Mar 2026 03:00:17 +0000
Subject: [PATCH 12/12] clang-format again

---
 include/beman/task/detail/awaiter.hpp | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/include/beman/task/detail/awaiter.hpp b/include/beman/task/detail/awaiter.hpp
index 2fbef7e..a6f4d9d 100644
--- a/include/beman/task/detail/awaiter.hpp
+++ b/include/beman/task/detail/awaiter.hpp
@@ -89,7 +89,9 @@ class awaiter : public ::beman::task::detail::state_base<Value, Env> {
         return this->no_completion_set() ? this->parent.promise().unhandled_stopped() : ::std::move(this->parent);
     }
     auto do_get_allocator() -> allocator_type override {
-        if constexpr (requires { ::beman::execution::get_allocator(::beman::execution::get_env(this->parent.promise())); })
+        if constexpr (requires {
+                          ::beman::execution::get_allocator(::beman::execution::get_env(this->parent.promise()));
+                      })
             return ::beman::execution::get_allocator(::beman::execution::get_env(this->parent.promise()));
         else
             return allocator_type{};