[Bug tree-optimization/118865] [12/13/14/15 regression] -Wfree-nonheap-object false positive

[snyder at bnl dot gov via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=118865

--- Comment #7 from scott snyder <snyder at bnl dot gov> ---
Thanks Andrew!

It appears that i was too aggressive in reducing the original source,
which as far as i can tell does handle empty containers properly.
For the record, it can be seen here (not my code, BTW...):
https://gitlab.cern.ch/atlas/athena/-/blob/main/Reconstruction/Jet/JetMonitoring/src/JetHistoResponseAndEff.cxx?ref_type=heads#L65

Here's another attempt at reducing this that should handle properly the case
of empty input containers:

-- test2.cc ------------------------------------------------------------
#include <list>
#include <cmath>

void foo(double);
double dist (int, int);

void processJetContainer(const int* jbeg, const int* jend,
                         const int* rbeg, const int* rend)
{
  using lint = std::list<int>;

  if (jbeg == jend) return;
  lint listJets(jbeg, jend);

  for (; rbeg < rend; ++rbeg)
  {
    double dr2min = 500000;

    if (listJets.empty() ) break;
    lint::iterator it=listJets.begin();
    lint::iterator itmin=it;
    for( ; it != listJets.end(); ++it) {
      double dr2 = dist(*it, *rbeg);
      if(dr2 < dr2min) { dr2min = dr2; itmin = it ;}
    }

    listJets.erase(itmin);
    foo (sqrt(dr2min));
  }
}
------------------------------------------------------------------------


This does not warn with gcc14, but does with gcc15, even with your
proposed patch.

$ g++ -c x.cc -O1
In file included from
/usr/local/gcc/include/c++/15.0.1/x86_64-pc-linux-gnu/bits/c++allocator.h:33,
                 from /usr/local/gcc/include/c++/15.0.1/bits/allocator.h:46,
                 from /usr/local/gcc/include/c++/15.0.1/list:65,
                 from x.cc:1:
In member function ‘void std::__new_allocator<_Tp>::deallocate(_Tp*, size_type)
[with _Tp = std::_List_node<int>]’,
    inlined from ‘static void std::allocator_traits<std::allocator<_Tp1>
>::deallocate(allocator_type&, pointer, size_type) [with _Tp =
std::_List_node<int>]’ at
/usr/local/gcc/include/c++/15.0.1/bits/alloc_traits.h:649:23,
    inlined from ‘void std::__cxx11::_List_base<_Tp,
_Alloc>::_M_put_node(_Node_ptr) [with _Tp = int; _Alloc = std::allocator<int>]’
at /usr/local/gcc/include/c++/15.0.1/bits/stl_list.h:820:32,
    inlined from ‘void std::__cxx11::_List_base<_Tp,
_Alloc>::_M_destroy_node(_Node_ptr) [with _Tp = int; _Alloc =
std::allocator<int>]’ at
/usr/local/gcc/include/c++/15.0.1/bits/stl_list.h:855:19,
    inlined from ‘void std::__cxx11::list<_Tp, _Allocator>::_M_erase(iterator)
[with _Tp = int; _Alloc = std::allocator<int>]’ at
/usr/local/gcc/include/c++/15.0.1/bits/stl_list.h:2485:23,
    inlined from ‘std::__cxx11::list<_Tp, _Allocator>::iterator
std::__cxx11::list<_Tp, _Allocator>::erase(const_iterator) [with _Tp = int;
_Alloc = std::allocator<int>]’ at
/usr/local/gcc/include/c++/15.0.1/bits/list.tcc:153:15,
    inlined from ‘void processJetContainer(const int*, const int*, const int*,
const int*)’ at x.cc:27:19:
/usr/local/gcc/include/c++/15.0.1/bits/new_allocator.h:172:66: warning: ‘void
operator delete(void*, std::size_t)’ called on unallocated object ‘listJets’
[-Wfree-nonheap-object]
  172 |         _GLIBCXX_OPERATOR_DELETE(_GLIBCXX_SIZED_DEALLOC(__p, __n));
      |                                                                  ^
x.cc: In function ‘void processJetContainer(const int*, const int*, const int*,
const int*)’:
x.cc:13:8: note: declared here
   13 |   lint listJets(jbeg, jend);
      |        ^~~~~~~~
$