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* [Bug c++/103563] New: ostream operator<< resolved to variant containing type resulting in stack overflow @ 2021-12-05 10:41 samuel.hangouet at gmail dot com 2021-12-05 11:07 ` [Bug c++/103563] " pinskia at gcc dot gnu.org ` (3 more replies) 0 siblings, 4 replies; 5+ messages in thread From: samuel.hangouet at gmail dot com @ 2021-12-05 10:41 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103563 Bug ID: 103563 Summary: ostream operator<< resolved to variant containing type resulting in stack overflow Product: gcc Version: 11.1.0 Status: UNCONFIRMED Severity: normal Priority: P3 Component: c++ Assignee: unassigned at gcc dot gnu.org Reporter: samuel.hangouet at gmail dot com Target Milestone: --- Created attachment 51928 --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=51928&action=edit Minimal test case. $ g++-11 --version g++-11 (Ubuntu 11.1.0-1ubuntu1~20.04) 11.1.0 (...) $ g++-11 -std=c++2a test.cpp -o test $ ./test Segmentation fault (core dumped) In my opinion, this file should not compile as no operator<< is provided for custom type V. Instead, the operator<< taking the variant which contains V is called, resulting in stack overflow at runtime. ^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug c++/103563] ostream operator<< resolved to variant containing type resulting in stack overflow 2021-12-05 10:41 [Bug c++/103563] New: ostream operator<< resolved to variant containing type resulting in stack overflow samuel.hangouet at gmail dot com @ 2021-12-05 11:07 ` pinskia at gcc dot gnu.org 2021-12-05 11:17 ` pinskia at gcc dot gnu.org ` (2 subsequent siblings) 3 siblings, 0 replies; 5+ messages in thread From: pinskia at gcc dot gnu.org @ 2021-12-05 11:07 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103563 Andrew Pinski <pinskia at gcc dot gnu.org> changed: What |Removed |Added ---------------------------------------------------------------------------- Status|UNCONFIRMED |RESOLVED Resolution|--- |INVALID --- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> --- No because std::variant has the following constructor: template< class T > constexpr variant( T&& t ) noexcept(/* see below */); So it is calling that. This constructor is not marked as explicit either. ^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug c++/103563] ostream operator<< resolved to variant containing type resulting in stack overflow 2021-12-05 10:41 [Bug c++/103563] New: ostream operator<< resolved to variant containing type resulting in stack overflow samuel.hangouet at gmail dot com 2021-12-05 11:07 ` [Bug c++/103563] " pinskia at gcc dot gnu.org @ 2021-12-05 11:17 ` pinskia at gcc dot gnu.org 2021-12-06 16:09 ` m.cencora at gmail dot com 2021-12-15 10:10 ` samuel.hangouet at gmail dot com 3 siblings, 0 replies; 5+ messages in thread From: pinskia at gcc dot gnu.org @ 2021-12-05 11:17 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103563 --- Comment #2 from Andrew Pinski <pinskia at gcc dot gnu.org> --- The following code is same example but removed the headers and such: namespace t { class g{}cout; template<class ...T> struct v { template <class T1> v(T1&&){} }; class monostate {}; g &operator <<(g &out, const char *a); } struct V { int a; }; inline t::g& operator << (t::g& os, const t::v<t::monostate, V>& a) { V v; os << v; return os; } int main() { V v={4}; t::cout << v; return 0; } ^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug c++/103563] ostream operator<< resolved to variant containing type resulting in stack overflow 2021-12-05 10:41 [Bug c++/103563] New: ostream operator<< resolved to variant containing type resulting in stack overflow samuel.hangouet at gmail dot com 2021-12-05 11:07 ` [Bug c++/103563] " pinskia at gcc dot gnu.org 2021-12-05 11:17 ` pinskia at gcc dot gnu.org @ 2021-12-06 16:09 ` m.cencora at gmail dot com 2021-12-15 10:10 ` samuel.hangouet at gmail dot com 3 siblings, 0 replies; 5+ messages in thread From: m.cencora at gmail dot com @ 2021-12-06 16:09 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103563 m.cencora at gmail dot com changed: What |Removed |Added ---------------------------------------------------------------------------- CC| |m.cencora at gmail dot com --- Comment #3 from m.cencora at gmail dot com --- This is a known issue with operators in C++ in general. That's why coding guidelines suggest that operators should be declared as hidden friends (to prevent unexpected implicit conversions). In your scenario you cannot make it a hidden friend, so constraint it with a concept or SFINAE: https://godbolt.org/z/de869vW6h ^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug c++/103563] ostream operator<< resolved to variant containing type resulting in stack overflow 2021-12-05 10:41 [Bug c++/103563] New: ostream operator<< resolved to variant containing type resulting in stack overflow samuel.hangouet at gmail dot com ` (2 preceding siblings ...) 2021-12-06 16:09 ` m.cencora at gmail dot com @ 2021-12-15 10:10 ` samuel.hangouet at gmail dot com 3 siblings, 0 replies; 5+ messages in thread From: samuel.hangouet at gmail dot com @ 2021-12-15 10:10 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103563 --- Comment #4 from Samuel Hangouët <samuel.hangouet at gmail dot com> --- Ok. Thanks for the tip and sorry for the wrong report. ^ permalink raw reply [flat|nested] 5+ messages in thread
end of thread, other threads:[~2021-12-15 10:10 UTC | newest] Thread overview: 5+ messages (download: mbox.gz / follow: Atom feed) -- links below jump to the message on this page -- 2021-12-05 10:41 [Bug c++/103563] New: ostream operator<< resolved to variant containing type resulting in stack overflow samuel.hangouet at gmail dot com 2021-12-05 11:07 ` [Bug c++/103563] " pinskia at gcc dot gnu.org 2021-12-05 11:17 ` pinskia at gcc dot gnu.org 2021-12-06 16:09 ` m.cencora at gmail dot com 2021-12-15 10:10 ` samuel.hangouet at gmail dot com
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