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* [Bug libstdc++/108556] New: std::sort changes objects' member values
@ 2023-01-26 10:05 gnu.iodaj at simplelogin dot com
2023-01-26 10:06 ` [Bug libstdc++/108556] " gnu.iodaj at simplelogin dot com
` (3 more replies)
0 siblings, 4 replies; 5+ messages in thread
From: gnu.iodaj at simplelogin dot com @ 2023-01-26 10:05 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108556
Bug ID: 108556
Summary: std::sort changes objects' member values
Product: gcc
Version: 11.3.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: libstdc++
Assignee: unassigned at gcc dot gnu.org
Reporter: gnu.iodaj at simplelogin dot com
Target Milestone: ---
When working on a project, I tried using std::sort to sort a vector of objects,
and it resulted in a crash. After looking closer, valgrind reports lots of
invalid writes and the data is effectively modified during the sort.
This issue doesn't happen with stable_sort nor with small enough vectors.
The g++ versions tested are 11.3.0 and 12.1.0.
The system is a Dell Precision 5570 running Linux Mint 21.
g++ command is g++ -Wall -Wextra sort-bug.cpp (file in attachment)
The compiler output is none (no warnings, no errors, no line displayed)
Please find the attached file that serves as a minimal working example of this
bug.
Thank you.
^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug libstdc++/108556] std::sort changes objects' member values
2023-01-26 10:05 [Bug libstdc++/108556] New: std::sort changes objects' member values gnu.iodaj at simplelogin dot com
@ 2023-01-26 10:06 ` gnu.iodaj at simplelogin dot com
2023-01-26 10:20 ` redi at gcc dot gnu.org
` (2 subsequent siblings)
3 siblings, 0 replies; 5+ messages in thread
From: gnu.iodaj at simplelogin dot com @ 2023-01-26 10:06 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108556
--- Comment #1 from gnu.iodaj at simplelogin dot com ---
Created attachment 54347
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=54347&action=edit
source file
^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug libstdc++/108556] std::sort changes objects' member values
2023-01-26 10:05 [Bug libstdc++/108556] New: std::sort changes objects' member values gnu.iodaj at simplelogin dot com
2023-01-26 10:06 ` [Bug libstdc++/108556] " gnu.iodaj at simplelogin dot com
@ 2023-01-26 10:20 ` redi at gcc dot gnu.org
2023-01-26 10:23 ` redi at gcc dot gnu.org
2023-07-14 19:04 ` pinskia at gcc dot gnu.org
3 siblings, 0 replies; 5+ messages in thread
From: redi at gcc dot gnu.org @ 2023-01-26 10:20 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108556
--- Comment #2 from Jonathan Wakely <redi at gcc dot gnu.org> ---
Compiling with -D_GLIBCXX_DEBUG shows the problem:
/home/jwakely/gcc/13/include/c++/13.0.1/bits/stl_algo.h:4892:
In function:
void std::sort(_RAIter, _RAIter, _Compare) [with _RAIter =
gnu_debug::_Safe_iterator<gnu_cxx::normal_iterator<Item*, vector<Item,
allocator<Item> > >, debug::vector<Item>, random_access_iterator_tag>;
_Compare = main()::<lambda(const Item&, const Item&)>]
Error: comparison doesn't meet irreflexive requirements, assert(!(a < a)).
Objects involved in the operation:
instance "functor" @ 0x7ffee875415f {
type = main::{lambda(Item const&, Item const&)#1};
}
iterator::value_type "ordered type" {
type = Item;
}
Aborted (core dumped)
Your comparison function fails to meet the requirements of a strict weak
ordering, so your program has undefined behaviour.
https://www.boost.org/sgi/stl/StrictWeakOrdering.html
https://en.cppreference.com/w/cpp/named_req/Compare
^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug libstdc++/108556] std::sort changes objects' member values
2023-01-26 10:05 [Bug libstdc++/108556] New: std::sort changes objects' member values gnu.iodaj at simplelogin dot com
2023-01-26 10:06 ` [Bug libstdc++/108556] " gnu.iodaj at simplelogin dot com
2023-01-26 10:20 ` redi at gcc dot gnu.org
@ 2023-01-26 10:23 ` redi at gcc dot gnu.org
2023-07-14 19:04 ` pinskia at gcc dot gnu.org
3 siblings, 0 replies; 5+ messages in thread
From: redi at gcc dot gnu.org @ 2023-01-26 10:23 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108556
Jonathan Wakely <redi at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|UNCONFIRMED |RESOLVED
Resolution|--- |INVALID
--- Comment #3 from Jonathan Wakely <redi at gcc dot gnu.org> ---
std::sort(items.begin(), items.end(), [](const Item &i, const Item &j) {
return i.getHeight() >= j.getHeight();
});
The bug is here. For a strict weak ordering cmp(x, x) must be false, because an
object must no be ordered before/after itself. Your lambda fails that
requirement, because it returns true when called with equivalent values.
^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug libstdc++/108556] std::sort changes objects' member values
2023-01-26 10:05 [Bug libstdc++/108556] New: std::sort changes objects' member values gnu.iodaj at simplelogin dot com
` (2 preceding siblings ...)
2023-01-26 10:23 ` redi at gcc dot gnu.org
@ 2023-07-14 19:04 ` pinskia at gcc dot gnu.org
3 siblings, 0 replies; 5+ messages in thread
From: pinskia at gcc dot gnu.org @ 2023-07-14 19:04 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108556
Andrew Pinski <pinskia at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Resolution|INVALID |DUPLICATE
--- Comment #4 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
dup
*** This bug has been marked as a duplicate of bug 553 ***
^ permalink raw reply [flat|nested] 5+ messages in thread
end of thread, other threads:[~2023-07-14 19:04 UTC | newest]
Thread overview: 5+ messages (download: mbox.gz / follow: Atom feed)
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2023-01-26 10:05 [Bug libstdc++/108556] New: std::sort changes objects' member values gnu.iodaj at simplelogin dot com
2023-01-26 10:06 ` [Bug libstdc++/108556] " gnu.iodaj at simplelogin dot com
2023-01-26 10:20 ` redi at gcc dot gnu.org
2023-01-26 10:23 ` redi at gcc dot gnu.org
2023-07-14 19:04 ` pinskia at gcc dot gnu.org
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