https://gcc.gnu.org/bugzilla/show_bug.cgi?id=118014
Bug ID: 118014
Summary: address computation for coroutine frame differs
between BasePromise and MostDerivedPromise
Product: gcc
Version: 14.1.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: giel+gcc at mortis dot eu
Target Milestone: ---
Created attachment 59845
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=59845&action=edit
reproduction scenario
Given the signature of
std::coroutine_handle<Promise>::from_promise(Promise& p)
(from: )
I expect to be able to do
struct MostDerivedPromise final : BasePromise {
auto await_transform(auto&& x) {
return
wrapped_awaitable(std::coroutine_handle<BasePromise>::from_promise(*this));
}
};
And then be able to use the produced handle both to access the (base part of
the) promise and to call .resume()/.destroy()/.done() on it.
Converting back to the promise reference works just fine. But .resume() and
.destroy() end up calling a NULL function pointer.
This appears to be caused by the conversion functions from/to handles&promises
depend on the alignment of the promise:
https://gcc.gnu.org/git/?p=gcc.git;a=blob;f=gcc/coroutine-passes.cc;h=c0d6eca7c070bbff391a07ce51d05d7010ff24c9;hb=04696df09633baf97cdbbdd6e9929b9d472161d3#l118
And obviously the alignment of MostDerivedPromise is unknown to
std::coroutine_handle<BasePromise> causing wrong offset calculations for this
scenario.
I've attached a reproduction scenario that has a single assertion for my
expectation that the underlying address produced for
coroutine_handle<BasePromise>::from_promise and
coroutine_handle<MostDerivedPromise> is the same.
That assertion holds when MostDerivedPromise' alignment is equal to that of
BasePromise but fails otherwise.
