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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)
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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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