[Bug c++/98052] New: Allocation with new and deallocation with std::allocator should result in an error

["src at andyf dot de" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98052

            Bug ID: 98052
           Summary: Allocation with new and deallocation with
                    std::allocator should result in an error
           Product: gcc
           Version: 10.2.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: src at andyf dot de
  Target Milestone: ---

Hello,

the following code compiles without an error (https://godbolt.org/z/oPG8Ea) in
GCC:


#include <memory>

constexpr auto fun()
{
    int* i = new int{4};

    std::allocator<int> a{};
    a.deallocate(i, 1);

    return 0;
}

int main()
{
    constexpr auto f = fun();
}


In the constexpr function fun, an int is allocated with new and free'd with
std::allocator's deallocate. According to N4868 [allocator.members] p6, a
precondition for deallocate is that the memory was previously allocated with
allocate. Clang does reject the code with:

note: 'std::allocator<...>::deallocate' used to delete pointer to object
allocated with 'new'

The behavior of Clang seems to be consistent with the wording. GCC incorrectly
allows this code to compile.


Best,

   Andreas