[Bug c++/98424] New: The point of destroying temporary objects when initializing an array

[Bug c++/98424] New: The point of destroying temporary objects when initializing an array

[xmh970252187 at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98424

            Bug ID: 98424
           Summary: The point of destroying temporary objects when
                    initializing an array
           Product: gcc
           Version: 10.2.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: xmh970252187 at gmail dot com
  Target Milestone: ---

#include <iostream>
struct A{
    A(int id):id_(id){}
    ~A(){
      std::cout<<"destroy A with id: "<<id_<<"\n";
    }
    int id_;
};
struct B{
    B(A const&){
       std::cout<<"construct from A\n";
    }
};
int main(){
    B arr[2] = {{0},{1}};
}

GCC destroy each temporary object that was bound to the parameter of `B(A
const&)` before initializing the next element.  

The print is https://godbolt.org/z/j9MMqE:  
````
construct from A
destroy A with id: 0
construct from A
destroy A with id: 1
````  
According to
[class.temporary#6.1](https://timsong-cpp.github.io/cppwp/n4659/class.temporary#6.1). 

>A temporary object bound to a reference parameter in a function call persists until the completion of the full-expression containing the call.  

That means all temporary objects should be destroyed after the initialization
for `arr` has completed. Presumably, it is a bug of GCC that when to destroy
these temporary objects

[Bug c++/98424] The point of destroying temporary objects when initializing an array

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98424

--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Hmm, ICC and MSVC both have the same behavior as GCC.

[Bug c++/98424] The point of destroying temporary objects when initializing an array

[xmh970252187 at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98424

--- Comment #2 from jim x <xmh970252187 at gmail dot com> ---
Clang destroys them at the end of the full-expression, see
https://godbolt.org/z/3xhPjoh8c

[Bug c++/98424] The point of destroying temporary objects when initializing an array

[ppalka at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98424

Patrick Palka <ppalka at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           See Also|                            |https://gcc.gnu.org/bugzill
                   |                            |a/show_bug.cgi?id=94041
                 CC|                            |ppalka at gcc dot gnu.org
   Target Milestone|---                         |12.0

--- Comment #3 from Patrick Palka <ppalka at gcc dot gnu.org> ---
It seems this is fixed for GCC 12+ by r12-6328-gbeaee0a871b648.