[Bug c++/106174] New: c++20: compilation fails erroneously with "deallocation of already deallocated storage"

[Bug c++/106174] New: c++20: compilation fails erroneously with "deallocation of already deallocated storage"

[janpmoeller at gmx dot de]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106174

            Bug ID: 106174
           Summary: c++20: compilation fails erroneously with
                    "deallocation of already deallocated storage"
           Product: gcc
           Version: 12.1.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: janpmoeller at gmx dot de
  Target Milestone: ---

The following c++20 source fails to compile on gcc 12.1 and current trunk:

////////////////////////////////////////////////////////////////////////////////
#include <array>
#include <memory>

struct test_vector
{
    constexpr ~test_vector() noexcept
    {
        m_allocator.deallocate(m_begin, m_capacity);
    }

    constexpr test_vector(std::size_t n)
        : m_begin(m_allocator.allocate(n))
        , m_capacity(n)
    {
    }

    constexpr test_vector(test_vector const& other)
        : test_vector(other.m_capacity)
    {
    }

    constexpr test_vector() = delete;
    constexpr test_vector(test_vector&& other) noexcept = delete;
    constexpr auto operator=(test_vector const& other) -> test_vector& =
delete;
    constexpr auto operator=(test_vector&& other) noexcept -> test_vector& =
delete;

    std::allocator<int> m_allocator{};
    int*                m_begin;
    std::size_t         m_capacity;
};

static_assert( // This fails with "deallocation of already deallocated storage"
    []
    {
        std::array<test_vector, 1> const values{test_vector(42)};
        std::array<test_vector, 1> const copy = values;
        return true;
    }());
////////////////////////////////////////////////////////////////////////////////

The compiler outputs:
<source>:46:6: error: non-constant condition for static assertion
   41 |     []
      |     ~~
   42 |     {
      |     ~ 
   43 |         std::array<test_vector, 1> const values{test_vector(42)};
      |         ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   44 |         std::array<test_vector, 1> const copy = values;
      |         ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   45 |         return true;
      |         ~~~~~~~~~~~~
   46 |     }());
      |     ~^~
In file included from
/opt/compiler-explorer/gcc-trunk-20220703/include/c++/13.0.0/memory:64,
                 from <source>:2:
<source>:46:6:   in 'constexpr' expansion of '<lambda closure
object><lambda()>().<lambda()>()'
<source>:46:5:   in 'constexpr' expansion of '((std::array<test_vector, 1>*)(&
copy))->std::array<test_vector, 1>::~array()'
/opt/compiler-explorer/gcc-trunk-20220703/include/c++/13.0.0/array:94:12:   in
'constexpr' expansion of '<anonymous>->test_vector::~test_vector()'
<source>:8:31:   in 'constexpr' expansion of
'((test_vector*)this)->test_vector::m_allocator.std::allocator<int>::deallocate(((test_vector*)this)->test_vector::m_begin,
((test_vector*)this)->test_vector::m_capacity)'
/opt/compiler-explorer/gcc-trunk-20220703/include/c++/13.0.0/bits/allocator.h:202:30:
error: deallocation of already deallocated storage
  202 |             ::operator delete(__p);
      |             ~~~~~~~~~~~~~~~~~^~~~~
Compiler returned: 1


Weirdly, the usage of std::array seems to be important here. I was unable to
reproduce this without the std::array. For example, the following variants
compile just fine:

// 1) This is accepted
test_vector const values(42);
test_vector const copy = values;

// 2) This is accepted
test_vector const values(42);
std::array<test_vector, 1> const copy = {values};

// 3) This is accepted
std::array<test_vector, 1> const values{test_vector(42)};
test_vector const copy = values[0];

The above test case is also available on compiler explorer:
https://godbolt.org/z/6xvx4fx6E

[Bug c++/106174] c++20: compilation fails erroneously with "deallocation of already deallocated storage"

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106174

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         Resolution|---                         |DUPLICATE
             Status|UNCONFIRMED                 |RESOLVED

--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
This is the same issue as PR 101777 which has a nice reduced testcase which
does not depend on the libstdc++ headers.

*** This bug has been marked as a duplicate of bug 101777 ***