https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106238
--- Comment #6 from Romain Geissler <romain.geissler at amadeus dot com> ---
Hi,
After upgrading to the latest gcc trunk, I have hit another variant of this
problem. For people just willing to exchange containers with swap, just
swapping the arguments makes it work, and actually has the same logic:
#include <set>
void f(std::set<int>& a)
{
std::set<int> b;
// b.swap(a); // Ok and has same effect
a.swap(b); // KO
}
Compiled on x86_64 with -O2 -Werror=dangling-pointer:
In file included from
/opt/compiler-explorer/gcc-trunk-20230314/include/c++/13.0.1/set:62,
from <source>:1:
In member function 'void std::_Rb_tree<_Key, _Val, _KeyOfValue, _Compare,
_Alloc>::swap(std::_Rb_tree<_Key, _Val, _KeyOfValue, _Compare, _Alloc>&) [with
_Key = int; _Val = int; _KeyOfValue = std::_Identity<int>; _Compare =
std::less<int>; _Alloc = std::allocator<int>]',
inlined from 'void std::set<_Key, _Compare, _Alloc>::swap(std::set<_Key,
_Compare, _Alloc>&) [with _Key = int; _Compare = std::less<int>; _Alloc =
std::allocator<int>]' at
/opt/compiler-explorer/gcc-trunk-20230314/include/c++/13.0.1/bits/stl_set.h:443:18,
inlined from 'void f(std::set<int>&)' at <source>:8:11:
/opt/compiler-explorer/gcc-trunk-20230314/include/c++/13.0.1/bits/stl_tree.h:2092:36:
error: storing the address of local variable 'b' in '*MEM[(struct
_Rb_tree_node_base * &)&b + 16].std::_Rb_tree_node_base::_M_parent'
[-Werror=dangling-pointer=]
2092 | __t._M_root()->_M_parent = __t._M_end();
| ~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~
<source>: In function 'void f(std::set<int>&)':
<source>:5:19: note: 'b' declared here
5 | std::set<int> b;
| ^
<source>:5:19: note: 'b.std::set<int, std::less<int>, std::allocator<int>
>::_M_t.std::_Rb_tree<int, int, std::_Identity<int>, std::less<int>,
std::allocator<int> >::_M_impl.std::_Rb_tree<int, int, std::_Identity<int>,
std::less<int>, std::allocator<int> >::_Rb_tree_impl<std::less<int>,
true>::<unnamed>.std::_Rb_tree_header::_M_header.std::_Rb_tree_node_base::_M_parent'
declared here
cc1plus: some warnings being treated as errors
Compiler returned: 1
