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* [Bug libstdc++/102712] New: std::optional::operator* should assert on unset value @ 2021-10-12 15:56 ott at fb dot com 2021-10-12 16:04 ` [Bug libstdc++/102712] " redi at gcc dot gnu.org ` (3 more replies) 0 siblings, 4 replies; 5+ messages in thread From: ott at fb dot com @ 2021-10-12 15:56 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102712 Bug ID: 102712 Summary: std::optional::operator* should assert on unset value Product: gcc Version: unknown Status: UNCONFIRMED Severity: normal Priority: P3 Component: libstdc++ Assignee: unassigned at gcc dot gnu.org Reporter: ott at fb dot com Target Milestone: --- It is UB to call operator* on an unset std::optional, and when doing so it is easy to hit time-traveling UB, resulting in behavior that is very hard to debug. For example, setting a field of an unset optional with operator-> may look like it succeeded, and the rest of the program will behave as if the optional was set, but it will silently leak memory because the destructor won't run. Another plausible scenario is having an optional<X> where X has an operator bool(), and spelling "if (*opt)" when the intention is to spell "if (opt)". The program compiles and the optional is just assumed set around the condition. Even UBSan with some of the strictest settings doesn't detect this. All major implementations of the type have defined behavior in debug builds: - libc++ asserts https://github.com/llvm-mirror/libcxx/blob/master/include/optional#L905 - boost asserts https://github.com/boostorg/optional/blob/develop/include/boost/optional/optional.hpp#L1213 - abseil asserts https://github.com/abseil/abseil-cpp/blob/master/absl/types/optional.h#L428 - folly throws (in any compilation mode) https://github.com/facebook/folly/blob/master/folly/Optional.h#L330 https://github.com/facebook/folly/blob/master/folly/Optional.h#L297 So anyone migrating from any of these is in for a world of hurt. Please consider adding an assertion in libstdc++. ^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug libstdc++/102712] std::optional::operator* should assert on unset value 2021-10-12 15:56 [Bug libstdc++/102712] New: std::optional::operator* should assert on unset value ott at fb dot com @ 2021-10-12 16:04 ` redi at gcc dot gnu.org 2021-10-12 16:06 ` redi at gcc dot gnu.org ` (2 subsequent siblings) 3 siblings, 0 replies; 5+ messages in thread From: redi at gcc dot gnu.org @ 2021-10-12 16:04 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102712 Jonathan Wakely <redi at gcc dot gnu.org> changed: What |Removed |Added ---------------------------------------------------------------------------- Status|UNCONFIRMED |RESOLVED Resolution|--- |WORKSFORME --- Comment #1 from Jonathan Wakely <redi at gcc dot gnu.org> --- You mean like this one? /usr/include/c++/11/optional:440: constexpr _Tp& std::_Optional_base_impl<_Tp, _Dp>::_M_get() [with _Tp = int; _Dp = std::_Optional_base<int, true, true>]: Assertion 'this->_M_is_engaged()' failed. Aborted (core dumped) It's been there since r248099 more than four years ago. Just compile with -D_GLIBCXX_ASSERTIONS ^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug libstdc++/102712] std::optional::operator* should assert on unset value 2021-10-12 15:56 [Bug libstdc++/102712] New: std::optional::operator* should assert on unset value ott at fb dot com 2021-10-12 16:04 ` [Bug libstdc++/102712] " redi at gcc dot gnu.org @ 2021-10-12 16:06 ` redi at gcc dot gnu.org 2021-10-12 16:09 ` ott at fb dot com 2022-11-28 11:08 ` redi at gcc dot gnu.org 3 siblings, 0 replies; 5+ messages in thread From: redi at gcc dot gnu.org @ 2021-10-12 16:06 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102712 --- Comment #2 from Jonathan Wakely <redi at gcc dot gnu.org> --- (In reply to Jonathan Wakely from comment #1) > Just compile with -D_GLIBCXX_ASSERTIONS Or the more heavyweight -D_GLIBCXX_DEBUG which implies _GLIBCXX_ASSERTIONS too. ^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug libstdc++/102712] std::optional::operator* should assert on unset value 2021-10-12 15:56 [Bug libstdc++/102712] New: std::optional::operator* should assert on unset value ott at fb dot com 2021-10-12 16:04 ` [Bug libstdc++/102712] " redi at gcc dot gnu.org 2021-10-12 16:06 ` redi at gcc dot gnu.org @ 2021-10-12 16:09 ` ott at fb dot com 2022-11-28 11:08 ` redi at gcc dot gnu.org 3 siblings, 0 replies; 5+ messages in thread From: ott at fb dot com @ 2021-10-12 16:09 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102712 --- Comment #3 from Giuseppe Ottaviano <ott at fb dot com> --- Oh well this is embarrassing, I was looking at _Optional_payload_base::_M_get() instead of _Optional_base_impl::_M_get() . Sorry for the noise and thanks for fixing this 4 years ago! ^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug libstdc++/102712] std::optional::operator* should assert on unset value 2021-10-12 15:56 [Bug libstdc++/102712] New: std::optional::operator* should assert on unset value ott at fb dot com ` (2 preceding siblings ...) 2021-10-12 16:09 ` ott at fb dot com @ 2022-11-28 11:08 ` redi at gcc dot gnu.org 3 siblings, 0 replies; 5+ messages in thread From: redi at gcc dot gnu.org @ 2022-11-28 11:08 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102712 Jonathan Wakely <redi at gcc dot gnu.org> changed: What |Removed |Added ---------------------------------------------------------------------------- CC| |tim at klingt dot org --- Comment #4 from Jonathan Wakely <redi at gcc dot gnu.org> --- *** Bug 107894 has been marked as a duplicate of this bug. *** ^ permalink raw reply [flat|nested] 5+ messages in thread
end of thread, other threads:[~2022-11-28 11:08 UTC | newest] Thread overview: 5+ messages (download: mbox.gz / follow: Atom feed) -- links below jump to the message on this page -- 2021-10-12 15:56 [Bug libstdc++/102712] New: std::optional::operator* should assert on unset value ott at fb dot com 2021-10-12 16:04 ` [Bug libstdc++/102712] " redi at gcc dot gnu.org 2021-10-12 16:06 ` redi at gcc dot gnu.org 2021-10-12 16:09 ` ott at fb dot com 2022-11-28 11:08 ` redi at gcc dot gnu.org
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