https://gcc.gnu.org/bugzilla/show_bug.cgi?id=116506
Bug ID: 116506
Summary: [15 Regression] Destructors of temporary awaitables
are executed too early
Product: gcc
Version: 15.0
Status: UNCONFIRMED
Keywords: c++-coroutines
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: daklishch at gmail dot com
CC: iains at gcc dot gnu.org
Target Milestone: ---
After r15-3146-g47dbd69b1, destructors of temporary awaitables are executed too
early (before suspending) if promise type has an await_transform. For example,
the following snippet executes __builtin_trap if compiled with the current
trunk but doesn't do so if compiled with GCC 14.2.1 or Clang 18.1.8.
```
$ cat ../test.cpp
#include <coroutine>
bool g_too_early = true;
std::coroutine_handle<> g_handle;
struct Awaiter {
Awaiter() {}
~Awaiter() {
if (g_too_early) {
__builtin_trap();
}
}
bool await_ready() { return false; }
void await_suspend(std::coroutine_handle<> handle) {
g_handle = handle;
}
void await_resume() {}
};
struct SuspendNever {
bool await_ready() noexcept { return true; }
void await_suspend(std::coroutine_handle<>) noexcept {}
void await_resume() noexcept {}
};
struct Coroutine {
struct promise_type {
Coroutine get_return_object() { return {}; }
SuspendNever initial_suspend() { return {}; }
SuspendNever final_suspend() noexcept { return {}; }
void return_void() {}
Awaiter&& await_transform(Awaiter&& u) {
return static_cast<Awaiter&&>(u);
}
};
};
Coroutine foo() {
co_await Awaiter{};
}
int main() {
foo();
g_too_early = false;
g_handle.destroy();
}
$ ~/gcc-15-trunk/bin/g++ ../test.cpp -o ../test.elf -std=c++20 -fno-exceptions
&& ../test.elf
zsh: illegal hardware instruction (core dumped) ../test.elf
$ g++ ../test.cpp -o ../test.elf -std=c++20 -fno-exceptions && ../test.elf
$ clang++ ../test.cpp -o ../test.elf -std=c++20 -fno-exceptions
-Wno-coroutine-missing-unhandled-exception && ../test.elf
```
CE link: https://godbolt.org/z/G7s35e4q8
