[Bug libstdc++/79486] [7 Regression] packaged_task uses wrong value category with result_of

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79486

Jonathan Wakely <redi at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |rejects-valid
             Status|UNCONFIRMED                 |ASSIGNED
   Last reconfirmed|                            |2017-02-13
      Known to work|                            |6.3.1
   Target Milestone|---                         |7.0
            Summary|[7 Regression]              |[7 Regression]
                   |                            |packaged_task uses wrong
                   |                            |value category with
                   |                            |result_of
     Ever confirmed|0                           |1

--- Comment #1 from Jonathan Wakely <redi at gcc dot gnu.org> ---
#include <future>

struct F {
  int& operator()() & { return i; }
  void operator()() && = delete;
  int i = 0;
};

int main()
{
  std::packaged_task<int()> t{F{}};
  t();
}

This fails to compie, and also gives an ICE (which I'll report separately)

In file included from task.cc:1:0:
/home/jwakely/gcc/7/include/c++/7.0.1/future: In instantiation of ‘struct
std::__future_base::_Task_state<_Fn, _Alloc, _Res(_Args ...)>::_M_run(_Args&&
...) [with _Fn = F; _Alloc = std::allocator<int>; _Res = int; _Args =
{}]::<lambda>’:
/home/jwakely/gcc/7/include/c++/7.0.1/future:1419:7:   required from ‘void
std::__future_base::_Task_state<_Fn, _Alloc, _Res(_Args ...)>::_M_run(_Args&&
...) [with _Fn = F; _Alloc = std::allocator<int>; _Res = int; _Args = {}]’
task.cc:13:1:   required from here
/home/jwakely/gcc/7/include/c++/7.0.1/future:1419:66: error: no type named
‘type’ in ‘class std::result_of<F()>’
  auto __boundfn = [&] () -> typename result_of<_Fn(_Args&&...)>::type {
                                                                  ^~~~
/home/jwakely/gcc/7/include/c++/7.0.1/future: In instantiation of ‘struct
std::__future_base::_Task_state<_Fn, _Alloc, _Res(_Args
...)>::_M_run_delayed(_Args&& ...,
std::weak_ptr<std::__future_base::_State_baseV2>) [with _Fn = F; _Alloc =
std::allocator<int>; _Res = int; _Args = {}]::<lambda>’:
/home/jwakely/gcc/7/include/c++/7.0.1/future:1428:7:   required from ‘void
std::__future_base::_Task_state<_Fn, _Alloc, _Res(_Args
...)>::_M_run_delayed(_Args&& ...,
std::weak_ptr<std::__future_base::_State_baseV2>) [with _Fn = F; _Alloc =
std::allocator<int>; _Res = int; _Args = {}]’
task.cc:13:1:   required from here
/home/jwakely/gcc/7/include/c++/7.0.1/future:1428:66: error: no type named
‘type’ in ‘class std::result_of<F()>’
  auto __boundfn = [&] () -> typename result_of<_Fn(_Args&&...)>::type {
                                                                  ^~~~
/home/jwakely/gcc/7/include/c++/7.0.1/future:600:7: error: ‘static
std::__future_base::_Task_setter<_Res_ptr, _BoundFn>
std::__future_base::_S_task_setter(_Res_ptr&, _BoundFn&) [with _Res_ptr =
std::unique_ptr<std::__future_base::_Result<int>,
std::__future_base::_Result_base::_Deleter>; _BoundFn =
std::__future_base::_Task_state<_Fn, _Alloc, _Res(_Args ...)>::_M_run(_Args&&
...) [with _Fn = F; _Alloc = std::allocator<int>; _Res = int; _Args =
{}]::<lambda>; typename _Res_ptr::element_type::result_type = int]’, declared
using local type ‘std::__future_base::_Task_state<_Fn, _Alloc, _Res(_Args
...)>::_M_run(_Args&& ...) [with _Fn = F; _Alloc = std::allocator<int>; _Res =
int; _Args = {}]::<lambda>’, is used but never defined [-fpermissive]
       _S_task_setter(_Res_ptr& __ptr, _BoundFn& __call)
       ^~~~~~~~~~~~~~
/home/jwakely/gcc/7/include/c++/7.0.1/future:600:7: error: ‘static
std::__future_base::_Task_setter<_Res_ptr, _BoundFn>
std::__future_base::_S_task_setter(_Res_ptr&, _BoundFn&) [with _Res_ptr =
std::unique_ptr<std::__future_base::_Result<int>,
std::__future_base::_Result_base::_Deleter>; _BoundFn =
std::__future_base::_Task_state<_Fn, _Alloc, _Res(_Args
...)>::_M_run_delayed(_Args&& ...,
std::weak_ptr<std::__future_base::_State_baseV2>) [with _Fn = F; _Alloc =
std::allocator<int>; _Res = int; _Args = {}]::<lambda>; typename
_Res_ptr::element_type::result_type = int]’, declared using local type
‘std::__future_base::_Task_state<_Fn, _Alloc, _Res(_Args
...)>::_M_run_delayed(_Args&& ...,
std::weak_ptr<std::__future_base::_State_baseV2>) [with _Fn = F; _Alloc =
std::allocator<int>; _Res = int; _Args = {}]::<lambda>’, is used but never
defined [-fpermissive]
/home/jwakely/gcc/7/include/c++/7.0.1/future: In instantiation of ‘static
std::__future_base::_Task_setter<_Res_ptr, _BoundFn>
std::__future_base::_S_task_setter(_Res_ptr&, _BoundFn&) [with _Res_ptr =
std::unique_ptr<std::__future_base::_Result<int>,
std::__future_base::_Result_base::_Deleter>; _BoundFn =
std::__future_base::_Task_state<_Fn, _Alloc, _Res(_Args
...)>::_M_run_delayed(_Args&& ...,
std::weak_ptr<std::__future_base::_State_baseV2>) [with _Fn = F; _Alloc =
std::allocator<int>; _Res = int; _Args = {}]::<lambda>]’:
/home/jwakely/gcc/7/include/c++/7.0.1/future:1426:7:   required from here
/home/jwakely/gcc/7/include/c++/7.0.1/future:600:7: internal compiler error:
Segmentation fault
0xdc0ddf crash_signal
        /home/jwakely/src/gcc/gcc/gcc/toplev.c:333
0x84c9b6 contains_struct_check(tree_node*, tree_node_structure_enum, char
const*, int, char const*)
        /home/jwakely/src/gcc/gcc/gcc/tree.h:3173
0x84c9b6 write_closure_type_name
        /home/jwakely/src/gcc/gcc/gcc/cp/mangle.c:1639
0x84c9b6 write_unqualified_name
        /home/jwakely/src/gcc/gcc/gcc/cp/mangle.c:1383
0x852717 write_name
        /home/jwakely/src/gcc/gcc/gcc/cp/mangle.c:937
0x8525bc write_local_name
        /home/jwakely/src/gcc/gcc/gcc/cp/mangle.c:2035
0x8525bc write_name
        /home/jwakely/src/gcc/gcc/gcc/cp/mangle.c:964
0x853209 write_class_enum_type
        /home/jwakely/src/gcc/gcc/gcc/cp/mangle.c:2777
0x853209 write_type
        /home/jwakely/src/gcc/gcc/gcc/cp/mangle.c:2195
0x8520e8 write_template_args
        /home/jwakely/src/gcc/gcc/gcc/cp/mangle.c:2806
0x85880d write_nested_name
        /home/jwakely/src/gcc/gcc/gcc/cp/mangle.c:1063
0x852457 write_name
        /home/jwakely/src/gcc/gcc/gcc/cp/mangle.c:976
0x8570d6 write_encoding
        /home/jwakely/src/gcc/gcc/gcc/cp/mangle.c:825
0x85915c mangle_decl_string
        /home/jwakely/src/gcc/gcc/gcc/cp/mangle.c:3757
0x8593ab get_mangled_id
        /home/jwakely/src/gcc/gcc/gcc/cp/mangle.c:3779
0x8593ab mangle_decl(tree_node*)
        /home/jwakely/src/gcc/gcc/gcc/cp/mangle.c:3849
0x1067f40 decl_assembler_name(tree_node*)
        /home/jwakely/src/gcc/gcc/gcc/tree.c:671
0x9aee1c symbol_table::insert_to_assembler_name_hash(symtab_node*, bool)
        /home/jwakely/src/gcc/gcc/gcc/symtab.c:171
0x9b4e3f cgraph_node::create(tree_node*)
        /home/jwakely/src/gcc/gcc/gcc/cgraph.c:511
0x9b4c90 cgraph_node::get_create(tree_node*)
        /home/jwakely/src/gcc/gcc/gcc/cgraph.c:533
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