[Bug bootstrap/78493] New: profiledbootstrap failure: error: attempt to free a non-heap object 'names' in ../../gcc/cp/parser.c:11482:23

[marxin at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78493

            Bug ID: 78493
           Summary: profiledbootstrap failure: error: attempt to free a
                    non-heap object 'names' in
                    ../../gcc/cp/parser.c:11482:23
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: bootstrap
          Assignee: unassigned at gcc dot gnu.org
          Reporter: marxin at gcc dot gnu.org
  Target Milestone: ---

I hit very interesting -Werror:

In file included from ../../gcc/hash-table.h:236:0,
                 from ../../gcc/coretypes.h:351,
                 from ../../gcc/cp/parser.c:23:
In static member function 'static void va_heap::release(vec<T, va_heap,
vl_embed>*&) [with T = tree_node*]',
    inlined from 'void vec<T, va_heap, vl_ptr>::release() [with T =
tree_node*]' at ../../gcc/vec.h:1497:3,
    inlined from 'auto_vec<T, N>::~auto_vec() [with T = tree_node*; long
unsigned int N = 16ul]' at ../../gcc/vec.h:1275:5,
    inlined from 'tree_node* cp_parser_range_for(cp_parser*, tree, tree, tree,
bool)' at ../../gcc/cp/parser.c:11482:23:
../../gcc/vec.h:307:3: error: attempt to free a non-heap object 'names'
[-Werror=free-nonheap-object]
   ::free (v);
   ^~

Problem is that function cp_parser_range_for uses auto_vec <tree, 16> names;
and as it only uses quick_push function, then m_vec == &m_auto:

  auto_vec ()
  {
    m_auto.embedded_init (MAX (N, 2), 0, 1);
    this->m_vec = &m_auto;
  }

and as ~auto_vec calls release:

template<typename T>
inline void
vec<T, va_heap, vl_ptr>::release (void)
{
  if (!m_vec)
    return;

  if (using_auto_storage ())
    {
      m_vec->m_vecpfx.m_num = 0;
      return;
    }

  va_heap::release (m_vec);
}

Because of we probably can't prove that m_vec->m_vecpfx.m_using_auto_storage ==
1, we end up with   free (&names.m_auto); which is a dead code.