https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102970
Bug ID: 102970
Summary: stable_sort uninitialized value with -funroll-loops
-fno-tree-vectorize
Product: gcc
Version: 11.2.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: dan at stahlke dot org
Target Milestone: ---
Created attachment 51682
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=51682&action=edit
demonstration source code
The attached file, compiled with 11.2.0, using the command line in the comment,
causes std::stable_sort to access uninitialized memory. In fact, it already
goes wrong by the time it passes the inputs to the first comparison operation.
The problem goes away if the copy constructor of the box struct is defaulted
(see the "#if").
It only happens with "-funroll-loops -fno-tree-vectorize".
Here is a Godbolt: https://godbolt.org/z/6PsdPj6q3
