[Bug tree-optimization/106238] Inline optimization causes dangling pointer on "include/c++/12.1.0/bits/stl_tree.h"

[romain.geissler at amadeus dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106238

Romain Geissler <romain.geissler at amadeus dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |romain.geissler at amadeus dot com

--- Comment #5 from Romain Geissler <romain.geissler at amadeus dot com> ---
Hi,

This seems to still happen with current trunk:


#include <map>

std::map<int, int> _Map;

void f()
{
    std::map<int, int> localMap;
    _Map.swap(localMap);
}

compiled with -Wall -Werror -O2:

In file included from
/opt/compiler-explorer/gcc-trunk-20230108/include/c++/13.0.0/map: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 = std::pair<const int, int>; _KeyOfValue =
std::_Select1st<std::pair<const int, int> >; _Compare = std::less<int>; _Alloc
= std::allocator<std::pair<const int, int> >]',
    inlined from 'void std::map<_Key, _Tp, _Compare,
_Alloc>::swap(std::map<_Key, _Tp, _Compare, _Alloc>&) [with _Key = int; _Tp =
int; _Compare = std::less<int>; _Alloc = std::allocator<std::pair<const int,
int> >]' at
/opt/compiler-explorer/gcc-trunk-20230108/include/c++/13.0.0/bits/stl_map.h:1172:18,
    inlined from 'void f()' at <source>:8:14:
/opt/compiler-explorer/gcc-trunk-20230108/include/c++/13.0.0/bits/stl_tree.h:2091:36:
error: storing the address of local variable 'localMap' in '*MEM[(struct
_Rb_tree_node_base * &)&localMap + 16].std::_Rb_tree_node_base::_M_parent'
[-Werror=dangling-pointer=]
 2091 |           __t._M_root()->_M_parent = __t._M_end();
      |           ~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~
<source>: In function 'void f()':
<source>:7:24: note: 'localMap' declared here
    7 |     std::map<int, int> localMap;
      |                        ^~~~~~~~
<source>:7:24: note: 'localMap.std::map<int, int, std::less<int>,
std::allocator<std::pair<const int, int> > >::_M_t.std::_Rb_tree<int,
std::pair<const int, int>, std::_Select1st<std::pair<const int, int> >,
std::less<int>, std::allocator<std::pair<const int, int> >
>::_M_impl.std::_Rb_tree<int, std::pair<const int, int>,
std::_Select1st<std::pair<const int, int> >, std::less<int>,
std::allocator<std::pair<const int, 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: all warnings being treated as errors
Compiler returned: 1


Cheers,
Romain