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From: "alois1@gmx-topmail.de" <gcc-bugzilla@gcc.gnu.org> To: gcc-bugs@gcc.gnu.org Subject: [Bug c++/101976] New: When constructing object, calling function and performing co_await in same statement, temporary is erroneously moved trivially Date: Thu, 19 Aug 2021 10:43:07 +0000 [thread overview] Message-ID: <bug-101976-4@http.gcc.gnu.org/bugzilla/> (raw) https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101976 Bug ID: 101976 Summary: When constructing object, calling function and performing co_await in same statement, temporary is erroneously moved trivially Product: gcc Version: 11.2.1 Status: UNCONFIRMED Severity: normal Priority: P3 Component: c++ Assignee: unassigned at gcc dot gnu.org Reporter: alois1@gmx-topmail.de Target Milestone: --- Created attachment 51324 --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=51324&action=edit Reduced preprocessed code GCC miscompiles the following C++ program: $ cat test.cpp #include <coroutine> struct task { struct promise_type { task get_return_object() { return {std::coroutine_handle<promise_type>::from_promise(*this)}; } std::suspend_never initial_suspend() { return {}; } std::suspend_never final_suspend() noexcept { return {}; } void unhandled_exception() {} void return_void() {} }; bool await_ready() { return true; } void await_suspend(std::coroutine_handle<>) {} void await_resume() { } std::coroutine_handle<promise_type> m_handle; }; extern "C" int puts(const char *s); struct nontrivial_move { nontrivial_move() { puts("nontrivial_move()"); } nontrivial_move(nontrivial_move &&) { puts("nontrivial_move(nontrivial_move &&)"); } ~nontrivial_move() { puts("~nontrivial_move()"); } char buf[128]{}; }; struct wrapper { nontrivial_move member; }; task subtask(wrapper) { co_return; } task main_task() { co_await subtask({}); } int main() { main_task(); } $ gcc -v Using built-in specs. COLLECT_GCC=/usr/bin/gcc COLLECT_LTO_WRAPPER=/usr/libexec/gcc/x86_64-redhat-linux/11/lto-wrapper OFFLOAD_TARGET_NAMES=nvptx-none OFFLOAD_TARGET_DEFAULT=1 Target: x86_64-redhat-linux Configured with: ../configure --enable-bootstrap --enable-languages=c,c++,fortran,objc,obj-c++,ada,go,d,lto --prefix=/usr --mandir=/usr/share/man --infodir=/usr/share/info --with-bugurl=http://bugzilla.redhat.com/bugzilla --enable-shared --enable-threads=posix --enable-checking=release --enable-multilib --with-system-zlib --enable-__cxa_atexit --disable-libunwind-exceptions --enable-gnu-unique-object --enable-linker-build-id --with-gcc-major-version-only --with-linker-hash-style=gnu --enable-plugin --enable-initfini-array --with-isl=/builddir/build/BUILD/gcc-11.2.1-20210728/obj-x86_64-redhat-linux/isl-install --enable-offload-targets=nvptx-none --without-cuda-driver --enable-gnu-indirect-function --enable-cet --with-tune=generic --with-arch_32=i686 --build=x86_64-redhat-linux Thread model: posix Supported LTO compression algorithms: zlib zstd gcc version 11.2.1 20210728 (Red Hat 11.2.1-1) (GCC) $ g++ -std=c++20 test.cpp; ./a.out nontrivial_move() nontrivial_move(nontrivial_move &&) ~nontrivial_move() ~nontrivial_move() ~nontrivial_move() Examination of the generated assembly code shows that the temporary wrapper object is erroneously copied under the assumption that it has trivial move constructor (the large buffer in nontrivial_move is just there to make this fact obvious). This behavior does not happen if the construction of the wrapper object or the co_await happens in a separate statement. Furthermore, the behavior does not happen if the only argument of subtask is changed to have type nontrivial_move (the move is elided entirely in this case, which is acceptable as far as I can tell). A manually reduced version of the preprocessed code is attached, which I have confirmed to show the same behavior. I think that the observed incorrect behavior might be a symptom of the same underlying issue as one or more of the bugs 99576, 100611, 101243, 101367.
next reply other threads:[~2021-08-19 10:43 UTC|newest] Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top 2021-08-19 10:43 alois1@gmx-topmail.de [this message] 2022-08-11 23:05 ` [Bug c++/101976] " dprokoptsev at gmail dot com 2022-12-04 10:41 ` cvs-commit at gcc dot gnu.org 2024-02-05 14:18 ` redi at gcc dot gnu.org
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