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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - [coroutines] coroutines with potentially-throwing 'co_await promise.final_suspend()' expressions should be ill-formed"
href="https://bugs.llvm.org/show_bug.cgi?id=46256">46256</a>
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<th>Summary</th>
<td>[coroutines] coroutines with potentially-throwing 'co_await promise.final_suspend()' expressions should be ill-formed
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<th>Product</th>
<td>clang
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<th>Version</th>
<td>trunk
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<th>Hardware</th>
<td>All
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<th>OS</th>
<td>All
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<th>Status</th>
<td>NEW
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<th>Severity</th>
<td>normal
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<th>Priority</th>
<td>P
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<th>Component</th>
<td>C++2a
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<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
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<th>Reporter</th>
<td>lewissbaker@gmail.com
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<th>CC</th>
<td>blitzrakete@gmail.com, erik.pilkington@gmail.com, llvm-bugs@lists.llvm.org, richard-llvm@metafoo.co.uk
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<pre>The wording of [dcl.fct.def.coroutine]/15 states:
<span class="quote">> The expression co_await promise.final_suspend() shall not be potentially-throwing ([except.spec]).</span >
See <a href="http://eel.is/c++draft/dcl.fct.def.coroutine#15">http://eel.is/c++draft/dcl.fct.def.coroutine#15</a>
and <a href="http://eel.is/c++draft/except.spec#6">http://eel.is/c++draft/except.spec#6</a>
I believe this means that the compiler should reject with a diagnostic any
coroutine with a promise_type where `co_await promise.final_suspend()` is not
noexcept. ie. all of the following must be declared noexcept (if they form part
of the await-expression):
- promise_type::final_suspend()
- finalSuspendObj.operator co_await()
- finalSuspendAwaiter.await_ready()
- finalSuspendAwaiter.await_suspend()
- finalSuspendAwaiter.await_resume()
- finalSuspedObj destructor
- finalSuspendAwaiter destructor
Clang (and GCC) currently accepts code that that does not declare
final_suspend() as
noexcept.
e.g. see <a href="https://godbolt.org/z/Et_5eo">https://godbolt.org/z/Et_5eo</a></pre>
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