.. _halo_task:

tmc::task
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``tmc::task<Result>`` supports HALO when used with Clang 20+ via the ``[[clang::coro_await_elidable]]`` attribute.

For HALO to work, the task coroutine function must be awaited directly as a prvalue in a ``co_await`` expression. Storing the task in a variable before awaiting prevents HALO from being applied.

.. code-block:: cpp

   // HALO: This allocation can be elided as it is directly awaited
   auto result = co_await task_int(1);

   // Non-HALO: This allocation cannot be elided as it is stored in a
   // variable before being awaited
   auto t = task_int(2);
   auto result = co_await std::move(t);

   // Non-HALO: This allocation cannot be elided because the .resume_on()
   // member function call breaks Clang's requirement that it be
   // an "immediate right-hand side operand to a co_await expression"
   auto result = co_await task_int(2).resume_on(tmc::current_executor());

Main Documentation
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For full documentation on ``tmc::task``, see :literal_ref:`tmc::task<task>`.