[Bug c++/34022] New: Rvalue references and std::forward() broken with built-in types

[Bug c++/34022] New: Rvalue references and std::forward() broken with built-in types

[eric dot niebler at gmail dot com]

Compile the following program with -std=c++0x. In my understanding, the two
printed addresses should be the same. They are when I invoke foo() with a class
type, but not with built-in types like char.

This is with the latest g++ built from SVN.

#include <cstdio>
#include <utility>

template<typename T> void bar(T &&t)
{
    std::printf("%p\n", &t);
}

template<typename T> void foo(T &&t)
{
    std::printf("%p\n", &t);
    bar(std::forward<T>(t));
}

struct S {};

int main()
{
    foo('a'); // WRONG, prints 2 different addresses
    foo(S()); // OK, prints the same address twice
}


-- 
           Summary: Rvalue references and std::forward() broken with built-
                    in types
           Product: gcc
           Version: 4.3.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: eric dot niebler at gmail dot com


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=34022

[Bug c++/34022] Rvalue references and std::forward() broken with built-in types

[pinskia at gcc dot gnu dot org]

------- Comment #1 from pinskia at gcc dot gnu dot org  2007-11-08 01:59 -------
  D.3322 = 97;
  printf (&"%p\n"[0], &D.3322);
  D.3373 = D.3322;
  printf (&"%p\n"[0], &D.3373);
  D.3323 = {};
  printf (&"%p\n"[0], &D.3323);
  printf (&"%p\n"[0], &D.3323);


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=34022

[Bug c++/34022] Rvalue references and std::forward() broken with built-in types

[pinskia at gcc dot gnu dot org]

------- Comment #2 from pinskia at gcc dot gnu dot org  2007-11-08 02:01 -------
<<cleanup_point <<< Unknown tree: expr_stmt
  bar ((char &) &TARGET_EXPR <D.3338, *forward ((char &) (char *) t)>) >>>
>>;

vs:
<<cleanup_point <<< Unknown tree: expr_stmt
  bar ((struct S &) (struct S *) forward ((struct S &) (struct S *) t)) >>>
>>;


-- 

pinskia at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
     Ever Confirmed|0                           |1
           Keywords|                            |wrong-code
   Last reconfirmed|0000-00-00 00:00:00         |2007-11-08 02:01:11
               date|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=34022

[Bug c++/34022] C++0x: rvalue references and std::forward() broken with built-in types

[dgregor at gcc dot gnu dot org]

------- Comment #3 from dgregor at gcc dot gnu dot org  2007-11-16 20:10 -------
I'm working on it


-- 

dgregor at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         AssignedTo|unassigned at gcc dot gnu   |dgregor at gcc dot gnu dot
                   |dot org                     |org
             Status|NEW                         |ASSIGNED
   Last reconfirmed|2007-11-08 02:01:11         |2007-11-16 20:10:50
               date|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=34022

[Bug c++/34022] C++0x: rvalue references and std::forward() broken with built-in types

[dgregor at gcc dot gnu dot org]

------- Comment #4 from dgregor at gcc dot gnu dot org  2007-11-18 14:15 -------
On further reading into the standard, I believe GCC is doing the right thing.
8.5.3p5 is very specific in saying that one can only bind a reference to an
rvalue if the type of the rvalue is of class type. Otherwise, a temporary is
being created.

If this isn't what Howard intended or expected, we need to bring this to the
committee.


-- 

dgregor at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|ASSIGNED                    |SUSPENDED


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=34022

[Bug c++/34022] C++0x: rvalue references and std::forward() broken with built-in types

[dgregor at gcc dot gnu dot org]

------- Comment #5 from dgregor at gcc dot gnu dot org  2008-03-19 13:12 -------
This is core issue 664:

  http://www.open-std.org/jtc1/sc22/wg21/docs/cwg_active.html#664


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=34022

[Bug c++/34022] C++0x: rvalue references and std::forward() broken with built-in types

[jason at gcc dot gnu dot org]

-- 

jason at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         AssignedTo|dgregor at gcc dot gnu dot  |unassigned at gcc dot gnu
                   |org                         |dot org
             Status|SUSPENDED                   |NEW


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=34022

[Bug c++/34022] C++0x: rvalue references and std::forward() broken with built-in types

[jwakely dot gcc at gmail dot com]

------- Comment #6 from jwakely dot gcc at gmail dot com  2009-06-02 14:14 -------
*** Bug 40295 has been marked as a duplicate of this bug. ***


-- 

jwakely dot gcc at gmail dot com changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |jwakely dot gcc at gmail dot
                   |                            |com


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=34022

[Bug c++/34022] C++0x: rvalue references and std::forward() broken with built-in types

[paolo dot carlini at oracle dot com]

------- Comment #7 from paolo dot carlini at oracle dot com  2009-08-01 09:45 -------
Appears also fixed by the fix for PR 40486. Otherwise, please reopen.


-- 

paolo dot carlini at oracle dot com changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|                            |FIXED
   Target Milestone|---                         |4.5.0


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=34022

[Bug c++/34022] C++0x: rvalue references and std::forward() broken with built-in types

[redi at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=34022

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |dgsteffen at numerica dot
                   |                            |us

--- Comment #8 from Jonathan Wakely <redi at gcc dot gnu.org> 2010-11-30 20:32:33 UTC ---
*** Bug 46732 has been marked as a duplicate of this bug. ***