.. _fork_group_fork_clang:

tmc::fork_group::fork_clang()
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``tmc::fork_group::fork_clang()`` is a HALO-optimized method for forking awaitables in a fork_group. It uses the ``[[clang::coro_await_elidable_argument]]`` attribute when compiled with Clang 20+.

For HALO to work, ``fork_clang()`` must be awaited directly as a prvalue in a ``co_await`` expression.

.. code-block:: cpp

   // HALO: fork_clang() is directly awaited for each task
   auto fg = tmc::fork_group<3, int>();
   co_await fg.fork_clang(task_int(5));
   co_await fg.fork_clang(task_int(6));
   co_await fg.fork_clang(task_int(7));
   auto results = co_await std::move(fg);

   // Non-HALO: fork() without HALO attributes
   auto fg = tmc::fork_group<3, int>();
   fg.fork(task_int(8));
   fg.fork(task_int(9));
   fg.fork(task_int(10));
   auto results = co_await std::move(fg);

**WARNING:** Do not use ``fork_clang()`` in a loop, as Clang will try to reuse the same allocation for multiple active coroutines, causing crashes.

.. code-block:: cpp

   // fork_clang() in a loop will cause a segfault!
   // Clang erroneously tries to use the same allocation for all subtasks
   auto fg = tmc::fork_group<3, int>();
   for (size_t i = 0; i < fg.capacity(); i++) {
     co_await fg.fork_clang(task_int(i));
   }
   auto results = co_await std::move(fg);

   // Correct: Use fork() without HALO attributes in a loop - works fine
   auto fg = tmc::fork_group<3, int>();
   for (size_t i = 0; i < fg.capacity(); i++) {
     fg.fork(task_int(i));
   }
   auto results = co_await std::move(fg);

Main Documentation
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For full documentation on ``tmc::fork_group``, including the non-HALO ``.fork()`` method, see :literal_ref:`tmc::fork_group<fork_group>`.