coroutine: preserve this->container before calling dtor #2246
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in `intermediate_task`, we intend to destroy the task right after
extracting the value from it, and then call `awaiter.process()`.
but GCC-14 warns at seeing this:
```
FAILED: tests/unit/CMakeFiles/test_unit_coroutines.dir/coroutines_test.cc.o
ccache /usr/bin/g++ -DBOOST_ALL_DYN_LINK -DFMT_SHARED -DSEASTAR_API_LEVEL=7 -DSEASTAR_DEFERRED_ACTION_REQUIRE_NOEXCEPT -DSEASTAR_HAS_MEMBARRIER -DSEASTAR_HAVE_ASAN_FIBER_SUPPORT -DSEASTAR_HAVE_HWLOC -DSEASTAR_HAVE_NUMA -DSEASTAR_HAVE_SYSTEMTAP_SDT -DSEASTAR_HAVE_URING -DSEASTAR_LOGGER_COMPILE_TIME_FMT -DSEASTAR_LOGGER_TYPE_STDOUT -DSEASTAR_SCHEDULING_GROUPS_COUNT=16 -DSEASTAR_SSTRING -DSEASTAR_TESTING_MAIN -DSEASTAR_TESTING_WITH_NETWORKING=1 -I/__w/seastar/seastar/tests/unit -I/__w/seastar/seastar/src -I/__w/seastar/seastar/include -I/__w/seastar/seastar/build/release/gen/include -I/__w/seastar/seastar/build/release/gen/src -O2 -g -DNDEBUG -std=gnu++23 -U_FORTIFY_SOURCE -Wno-maybe-uninitialized -Wno-error=unused-result -UNDEBUG -Wall -Werror -Wimplicit-fallthrough -Wdeprecated -Wno-error=deprecated -Wno-error=stringop-overflow -Wno-error=array-bounds -Wdeprecated-declarations -Wno-error=deprecated-declarations -fvisibility=hidden -gz -MD -MT tests/unit/CMakeFiles/test_unit_coroutines.dir/coroutines_test.cc.o -MF tests/unit/CMakeFiles/test_unit_coroutines.dir/coroutines_test.cc.o.d -o tests/unit/CMakeFiles/test_unit_coroutines.dir/coroutines_test.cc.o -c /__w/seastar/seastar/tests/unit/coroutines_test.cc
In file included from /__w/seastar/seastar/tests/unit/coroutines_test.cc:46:
/__w/seastar/seastar/include/seastar/coroutine/all.hh: In member function 'void seastar::coroutine::all<Futures>::intermediate_task<idx>::run_and_dispose() [with long unsigned int idx = 1; Futures = {seastar::future<void>, seastar::future<void>}]':
/__w/seastar/seastar/include/seastar/coroutine/all.hh:138:13: error: '*this.seastar::coroutine::all<seastar::future<void>, seastar::future<void> >::intermediate_task<1>::container' is used uninitialized [-Werror=uninitialized]
138 | container.template process<idx+1>();
| ^~~~~~~~~
```
it believes that after returning from the destructor of
`intermediate_task`, the instance is in an "uninitialized" state,
so if we reference any of its member variables. we could have
undefined behavior. this is a false alarm, as the destructor does
not change the value of `container` reference. but this could be
still confusing at first glance. so, to silence the warning, let's
preserve the `container` before calling the destructor, and use
the preserved reference to call `awaiter::process()`.
Signed-off-by: Kefu Chai <[email protected]>
|
@scylladb/seastar-maint hello maintainers, could you help review this change? |
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in
intermediate_task, we intend to destroy the task right after extracting the value from it, and then callawaiter.process(). but GCC-14 warns at seeing this:it believes that after returning from the destructor of
intermediate_task, the instance is in an "uninitialized" state, so if we reference any of its member variables. we could have undefined behavior. this is a false alarm, as the destructor does not change the value ofcontainerreference. but this could be still confusing at first glance. so, to silence the warning, let's preserve thecontainerbefore calling the destructor, and use the preserved reference to callawaiter::process().