[Bug c++/61973] New: __thread and deleted destructor

[Bug c++/61973] New: __thread and deleted destructor

[nyh at math dot technion.ac.il]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61973

            Bug ID: 61973
           Summary: __thread and deleted destructor
           Product: gcc
           Version: 4.8.2
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: nyh at math dot technion.ac.il

Hi, right now "__thread" insists that the given type has a trivial destructor.
There is unfortunately no way to silence this error, even when I deliberately
want this (e.g., I know I'll call ~T() explicitly in another way).

I figured out a way (see below) to *delete* a type's destructor, using a union
(see below). However, __thread only accepts a trivial destructor, not a deleted
destructor. Is there a reason __thread cannot accept a type with a deleted
destructor?

Bonus points to anyone who can figure out how I can use __thread (not
thread_local) on a type with a non-trivial destructor even in existing gcc ;-)

The code to "delete" a type's destructor:

template <class T>
class mask_destructor {
private:
    union {
        alignas(T) char bytes[sizeof(T)];
        T obj;
    };
public:
    T& get() const { return obj; }
    // preserve T's constexpr constructor
    constexpr mask_destructor() : obj() { }
    mask_destructor(const mask_destructor &other) : obj(other.obj) { }
    mask_destructor &operator=(const mask_destructor &other){
        obj = other.obj;
        return *this;
    }
    // Note no destructor defined. The compile implicitly deletes it
    // because of the anonymous union above.
};

[Bug c++/61973] __thread and deleted destructor

[paolo.carlini at oracle dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61973

Paolo Carlini <paolo.carlini at oracle dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |WAITING
   Last reconfirmed|                            |2015-03-27
     Ever confirmed|0                           |1

--- Comment #1 from Paolo Carlini <paolo.carlini at oracle dot com> ---
Please provide a self-contained snippet showing the issue.

[Bug c++/61973] __thread and deleted destructor

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61973

--- Comment #2 from Jonathan Wakely <redi at gcc dot gnu.org> ---
(In reply to Nadav Har'El from comment #0)
> Bonus points to anyone who can figure out how I can use __thread (not
> thread_local) on a type with a non-trivial destructor even in existing gcc
> ;-)

__thread std::aligned_storage<T>::type buf;
__thread T* obj = [&]{ return ::new(&buf) T(blah blah); }();

[Bug c++/61973] __thread and deleted destructor

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61973

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
         Resolution|---                         |WONTFIX
             Status|WAITING                     |RESOLVED

--- Comment #3 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
thread_local has become more wildly used than __thread.  GCC does a decent job
even of not emitting TLS initializers and such.  So closing as won't fix.