[Bug libstdc++/48113] New: [C++0x] bind with tuple argument fails

[Bug libstdc++/48113] New: [C++0x] bind with tuple argument fails

[martin.kronbichler at it dot uu.se]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48113

           Summary: [C++0x] bind with tuple argument fails
           Product: gcc
           Version: 4.6.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: libstdc++
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: martin.kronbichler@it.uu.se


Compiler version:

$ gcc-4.6 -v
Using built-in specs.
COLLECT_GCC=gcc-4.6
COLLECT_LTO_WRAPPER=/usr/lib/gcc/x86_64-linux-gnu/4.6.0/lto-wrapper
Target: x86_64-linux-gnu
Configured with: ../configure --enable-languages=c,c++,fortran,objc,obj-c++,go
--prefix=/usr --libexecdir=/usr/lib --enable-shared --enable-multiarch
--enable-linker-build-id --with-system-zlib --without-included-gettext
--enable-threads=posix --program-suffix=-4.6 --enable-nls --enable-clocale=gnu
--enable-libstdcxx-debug --enable-plugin --enable-objc-gc --disable-werror
--with-arch-32=i486 --with-tune=core2 --enable-checking=release
--build=x86_64-linux-gnu --host=x86_64-linux-gnu --target=x86_64-linux-gnu
--with-cpu=core2
Thread model: posix
gcc version 4.6.0 20110312 (experimental) (GCC) 

(weekly snapshot on x86_64)


On the following code:

#include <functional>
void test_1 (std::tuple<int>);
void test (int tst) {
  const std::function<void()> fun (std::bind(&test_1, std::tuple<int>(tst)));
};

with the command line "g++-4.6 -std=c++0x -c bind_test.cc -o bind_tst.o", I get
the following error message:

In file included from bind_test.cc:2:0:
/usr/lib/gcc/x86_64-linux-gnu/4.6.0/../../../../include/c++/4.6.0/functional:
In static member function ‘static void std::_Function_handler<void(_ArgTypes
...), _Functor>::_M_invoke(const std::_Any_data&, _ArgTypes ...) [with _Functor
= std::_Bind<void (*(std::tuple<int>))(std::tuple<int>)>, _ArgTypes = {}]’:
/usr/lib/gcc/x86_64-linux-gnu/4.6.0/../../../../include/c++/4.6.0/functional:2135:6:
  instantiated from ‘std::function<_Res(_ArgTypes ...)>::function(_Functor,
typename std::enable_if<(! std::is_integral<_Functor>::value),
std::function<_Res(_ArgTypes ...)>::_Useless>::type) [with _Functor =
std::_Bind<void (*(std::tuple<int>))(std::tuple<int>)>, _Res = void, _ArgTypes
= {}, typename std::enable_if<(! std::is_integral<_Functor>::value),
std::function<_Res(_ArgTypes ...)>::_Useless>::type =
std::function<void()>::_Useless]’
bind_test.cc:6:76:   instantiated from here
/usr/lib/gcc/x86_64-linux-gnu/4.6.0/../../../../include/c++/4.6.0/functional:1765:9:
error: no matching function for call to ‘std::tuple<int>::tuple(const volatile
std::tuple<int>&)’
/usr/lib/gcc/x86_64-linux-gnu/4.6.0/../../../../include/c++/4.6.0/functional:1765:9:
note: candidates are:
/usr/lib/gcc/x86_64-linux-gnu/4.6.0/../../../../include/c++/4.6.0/tuple:441:32:
note: template<class _U1> std::tuple<_T1>::tuple(std::tuple<_U1>&&)
/usr/lib/gcc/x86_64-linux-gnu/4.6.0/../../../../include/c++/4.6.0/tuple:437:37:
note: template<class _U1> std::tuple<_T1>::tuple(const std::tuple<_U1>&)
/usr/lib/gcc/x86_64-linux-gnu/4.6.0/../../../../include/c++/4.6.0/tuple:433:7:
note: std::tuple<_T1>::tuple(std::tuple<_T1>&&) [with _T1 = int,
std::tuple<_T1> = std::tuple<int>]
/usr/lib/gcc/x86_64-linux-gnu/4.6.0/../../../../include/c++/4.6.0/tuple:433:7:
note:   no known conversion for argument 1 from ‘const volatile
std::tuple<int>’ to ‘std::tuple<int>&&’
/usr/lib/gcc/x86_64-linux-gnu/4.6.0/../../../../include/c++/4.6.0/tuple:431:17:
note: constexpr std::tuple<_T1>::tuple(const std::tuple<_T1>&) [with _T1 = int,
std::tuple<_T1> = std::tuple<int>]
/usr/lib/gcc/x86_64-linux-gnu/4.6.0/../../../../include/c++/4.6.0/tuple:431:17:
note:   no known conversion for argument 1 from ‘const volatile
std::tuple<int>’ to ‘const std::tuple<int>&’
/usr/lib/gcc/x86_64-linux-gnu/4.6.0/../../../../include/c++/4.6.0/tuple:418:17:
note: constexpr std::tuple<_T1>::tuple() [with _T1 = int]
/usr/lib/gcc/x86_64-linux-gnu/4.6.0/../../../../include/c++/4.6.0/tuple:418:17:
note:   candidate expects 0 arguments, 1 provided
/usr/lib/gcc/x86_64-linux-gnu/4.6.0/../../../../include/c++/4.6.0/functional:1765:9:
error: no matching function for call to ‘std::tuple<int>::tuple(volatile
std::tuple<int>&)’
/usr/lib/gcc/x86_64-linux-gnu/4.6.0/../../../../include/c++/4.6.0/functional:1765:9:
note: candidates are:
/usr/lib/gcc/x86_64-linux-gnu/4.6.0/../../../../include/c++/4.6.0/tuple:441:32:
note: template<class _U1> std::tuple<_T1>::tuple(std::tuple<_U1>&&)
/usr/lib/gcc/x86_64-linux-gnu/4.6.0/../../../../include/c++/4.6.0/tuple:437:37:
note: template<class _U1> std::tuple<_T1>::tuple(const std::tuple<_U1>&)
/usr/lib/gcc/x86_64-linux-gnu/4.6.0/../../../../include/c++/4.6.0/tuple:433:7:
note: std::tuple<_T1>::tuple(std::tuple<_T1>&&) [with _T1 = int,
std::tuple<_T1> = std::tuple<int>]
/usr/lib/gcc/x86_64-linux-gnu/4.6.0/../../../../include/c++/4.6.0/tuple:433:7:
note:   no known conversion for argument 1 from ‘volatile std::tuple<int>’ to
‘std::tuple<int>&&’
/usr/lib/gcc/x86_64-linux-gnu/4.6.0/../../../../include/c++/4.6.0/tuple:431:17:
note: constexpr std::tuple<_T1>::tuple(const std::tuple<_T1>&) [with _T1 = int,
std::tuple<_T1> = std::tuple<int>]
/usr/lib/gcc/x86_64-linux-gnu/4.6.0/../../../../include/c++/4.6.0/tuple:431:17:
note:   no known conversion for argument 1 from ‘volatile std::tuple<int>’ to
‘const std::tuple<int>&’
/usr/lib/gcc/x86_64-linux-gnu/4.6.0/../../../../include/c++/4.6.0/tuple:418:17:
note: constexpr std::tuple<_T1>::tuple() [with _T1 = int]
/usr/lib/gcc/x86_64-linux-gnu/4.6.0/../../../../include/c++/4.6.0/tuple:418:17:
note:   candidate expects 0 arguments, 1 provided

Since I can't see anything illegal with the code, my guess is that it is a
problem with the C++0x headers (the compilation is fine with gcc 4.5.2 with
-std=c++0x argument).

[Bug libstdc++/48113] [C++0x] bind with tuple argument fails

[redi at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48113

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2011.03.14 14:09:41
     Ever Confirmed|0                           |1

--- Comment #1 from Jonathan Wakely <redi at gcc dot gnu.org> 2011-03-14 14:09:41 UTC ---
harrumph, I thought we'd solved these problems with the volatile overloads,
apparently not.  I'll look into it later

[Bug libstdc++/48113] [4.6 Regression] [C++0x] bind with tuple argument fails

[redi at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48113

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
            Summary|[4.6/4.7 Regression]        |[4.6 Regression] [C++0x]
                   |[C++0x] bind with tuple     |bind with tuple argument
                   |argument fails              |fails

--- Comment #2 from Jonathan Wakely <redi at gcc dot gnu.org> 2011-03-14 14:19:36 UTC ---
N.B. as a workaround you can specify the return type of the bind expression:

  std::bind<void>(&test_1, std::tuple<int>(tst))
           ^^^^^^

This avoids the problem code, which is trying to determine the return type.

[Bug libstdc++/48113] [4.6/4.7 Regression] [C++0x] bind with tuple argument fails

[rguenth at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48113

Richard Guenther <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|---                         |4.6.0
            Summary|[4.6 Regression] [C++0x]    |[4.6/4.7 Regression]
                   |bind with tuple argument    |[C++0x] bind with tuple
                   |fails                       |argument fails

[Bug libstdc++/48113] [4.6/4.7 Regression] [C++0x] bind with tuple argument fails

[redi at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48113

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |jason at gcc dot gnu.org

--- Comment #3 from Jonathan Wakely <redi at gcc dot gnu.org> 2011-03-14 16:22:44 UTC ---
Jason, could you take a look at this reduced testcase, which has no libstdc++
dependency?

template<typename T> T declval();

struct tuple { };

struct F1
{
    void operator()(tuple);
};

typedef void (*F2)(tuple);

template<typename F, typename T>
struct Bind
{
    decltype( F()(declval<T&>()) )
    f();

    decltype( F()(declval<volatile T&>()) )
    f() volatile;
};

int main()
{
    Bind<F1, tuple>().f();  // OK

    Bind<F2, tuple>().f();  // ERROR
}

This shows that SFINAE removes the Bind::f() volatile overload if F is a
functor, but not if it's a function pointer.  I can't see why it should be
different.

Is this a FE bug, or do I need to handle function pointers differently in
std::bind?  Thanks

[Bug libstdc++/48113] [4.6/4.7 Regression] [C++0x] bind with tuple argument fails

[jason at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48113

Jason Merrill <jason at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |ASSIGNED
         AssignedTo|unassigned at gcc dot       |jason at gcc dot gnu.org
                   |gnu.org                     |

--- Comment #4 from Jason Merrill <jason at gcc dot gnu.org> 2011-03-14 17:24:36 UTC ---
SFINAE is not removing an overload; it doesn't work like that.  SFINAE only
applies to function templates, not non-template member functions of class
templates.  It's just that for some reason we aren't complaining about the
functor case.  Reduced further:

struct A { };
volatile A& f();

struct F1
{
  void operator()(A);
};

typedef void (*F2)(A);

typedef decltype (F1()(f())) t1;
typedef decltype (F2()(f())) t2;

The inconsistency is odd.  I would expect both lines to give an error.

[Bug libstdc++/48113] [4.6/4.7 Regression] [C++0x] bind with tuple argument fails

[jason at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48113

Jason Merrill <jason at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|ASSIGNED                    |NEW
         AssignedTo|jason at gcc dot gnu.org    |unassigned at gcc dot
                   |                            |gnu.org

--- Comment #5 from Jason Merrill <jason at gcc dot gnu.org> 2011-03-14 17:33:44 UTC ---
Indeed, EDG 4.2 rejects both.  So the bug report is indeed a library issue. 
I'll open a separate report for the accepts-invalid example.

[Bug libstdc++/48113] [4.6/4.7 Regression] [C++0x] bind with tuple argument fails

[paolo.carlini at oracle dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48113

--- Comment #6 from Paolo Carlini <paolo.carlini at oracle dot com> 2011-03-14 17:55:53 UTC ---
I suspect Jon reduced the testcase a bit too much, because we have been through
this kind of discussion/misunderstanding already, indeed normally we have only
function *templates* in the actual code, no SFINAE to the help otherwise,
agreed.

Thanks Jon (and Jason) for looking into this.

[Bug libstdc++/48113] [4.6/4.7 Regression] [C++0x] bind with tuple argument fails

[redi at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48113

--- Comment #7 from Jonathan Wakely <redi at gcc dot gnu.org> 2011-03-14 18:01:51 UTC ---
Doh, yes I got carried away reducing it and made it no longer a template
function, so of course SFINAE doesn't apply - sorry!

Should it apply in the case below?

template<typename T> T declval();

struct tuple { };

struct F1
{
    void operator()(tuple);
};

typedef void (*F2)(tuple);

template<typename F, typename T>
struct Bind
{
    template<typename A, typename R = decltype( F()(declval<T&>()) )>
    R f(A);

    template<typename A, typename R = decltype( F()(declval<volatile T&>()) )>
    R f(A) volatile;
};

int main()
{
    Bind<F1, tuple>().f(0);  // OK

    Bind<F2, tuple>().f(0);  // ERROR
}

Currently Bind::f() volatile gives an error during overload resolution but the
other overload doesn't.  Will your fix make both fail?

[Bug libstdc++/48113] [4.6/4.7 Regression] [C++0x] bind with tuple argument fails

[redi at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48113

--- Comment #8 from Jonathan Wakely <redi at gcc dot gnu.org> 2011-03-14 18:03:52 UTC ---
(In reply to comment #7)
> Currently Bind::f() volatile gives an error during overload resolution but the
> other overload doesn't.  Will your fix make both fail?

brain really not firing today ... I meant:
Currently Bind::f() volatile gives an error for F2, but not F1. Will you fix
make both fail?

[Bug libstdc++/48113] [4.6/4.7 Regression] [C++0x] bind with tuple argument fails

[redi at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48113

--- Comment #9 from Jonathan Wakely <redi at gcc dot gnu.org> 2011-03-14 18:10:19 UTC ---
here's one even closer to what we actually have in the library, where the
default template argument R involves the deduced type A as well:

template<typename T> T declval();

struct tuple { };

struct F1
{
    void operator()(tuple, int);
};

typedef void (*F2)(tuple, int);

template<typename F, typename T>
struct Bind
{
    template<typename A,
             typename R = decltype( F()(declval<T&>(), A()) )>
    R f(A);

    template<typename A,
             typename R = decltype( F()(declval<volatile T&>(), A()) )>
    R f(A) volatile;
};

int main()
{
    Bind<F1, tuple>().f(0);  // OK

    Bind<F2, tuple>().f(0);  // ERROR
}

[Bug c++/48113] [4.6/4.7 Regression] [C++0x] bind with tuple argument fails

[jason at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48113

Jason Merrill <jason at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |ASSIGNED
          Component|libstdc++                   |c++
         AssignedTo|unassigned at gcc dot       |jason at gcc dot gnu.org
                   |gnu.org                     |

--- Comment #10 from Jason Merrill <jason at gcc dot gnu.org> 2011-03-14 18:47:53 UTC ---
That is indeed a SFINAE bug.

[Bug c++/48113] [4.6/4.7 Regression] [C++0x] bind with tuple argument fails

[redi at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48113

--- Comment #11 from Jonathan Wakely <redi at gcc dot gnu.org> 2011-03-14 18:59:45 UTC ---
(In reply to comment #10)
> That is indeed a SFINAE bug.

phew!  cos I'm all out of better ideas for fixing std::bind ;)

Thanks for your help, sorry for the mixup with my overeager testcase reduction,
but at least we found a new bug out of it

[Bug c++/48113] [4.6/4.7 Regression] [C++0x] bind with tuple argument fails

[jason at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48113

--- Comment #12 from Jason Merrill <jason at gcc dot gnu.org> 2011-03-16 20:03:07 UTC ---
Author: jason
Date: Wed Mar 16 20:03:01 2011
New Revision: 171064

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=171064
Log:
    PR c++/48113
    * typeck.c (convert_for_initialization): Use
    perform_implicit_conversion_flags.
    * call.c (standard_conversion): If LOOKUP_PREFER_RVALUE, set
    rvaluedness_matches_p on ck_rvalue.
    (convert_like_real) [ck_rvalue]: And restore it here.

Added:
    branches/gcc-4_6-branch/gcc/testsuite/g++.dg/cpp0x/sfinae6.C
Modified:
    branches/gcc-4_6-branch/gcc/cp/ChangeLog
    branches/gcc-4_6-branch/gcc/cp/call.c
    branches/gcc-4_6-branch/gcc/cp/typeck.c
    branches/gcc-4_6-branch/gcc/testsuite/ChangeLog
    branches/gcc-4_6-branch/gcc/testsuite/g++.dg/cpp0x/initlist38.C
    branches/gcc-4_6-branch/gcc/testsuite/g++.dg/cpp0x/pr45908.C
    branches/gcc-4_6-branch/gcc/testsuite/g++.old-deja/g++.jason/conversion11.C
    branches/gcc-4_6-branch/gcc/testsuite/g++.old-deja/g++.law/arg11.C

[Bug c++/48113] [4.6/4.7 Regression] [C++0x] bind with tuple argument fails

[jason at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48113

--- Comment #13 from Jason Merrill <jason at gcc dot gnu.org> 2011-03-16 20:04:01 UTC ---
Author: jason
Date: Wed Mar 16 20:03:56 2011
New Revision: 171067

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=171067
Log:
    PR c++/48113
    * typeck.c (convert_for_initialization): Use
    perform_implicit_conversion_flags.
    * call.c (standard_conversion): If LOOKUP_PREFER_RVALUE, set
    rvaluedness_matches_p on ck_rvalue.
    (convert_like_real) [ck_rvalue]: And restore it here.

Added:
    trunk/gcc/testsuite/g++.dg/cpp0x/sfinae6.C
Modified:
    trunk/gcc/cp/ChangeLog
    trunk/gcc/cp/call.c
    trunk/gcc/cp/typeck.c
    trunk/gcc/testsuite/ChangeLog
    trunk/gcc/testsuite/g++.dg/cpp0x/initlist38.C
    trunk/gcc/testsuite/g++.dg/cpp0x/pr45908.C
    trunk/gcc/testsuite/g++.old-deja/g++.jason/conversion11.C
    trunk/gcc/testsuite/g++.old-deja/g++.law/arg11.C

[Bug c++/48113] [4.6/4.7 Regression] [C++0x] bind with tuple argument fails

[jason at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48113

Jason Merrill <jason at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|ASSIGNED                    |RESOLVED
         Resolution|                            |FIXED

--- Comment #14 from Jason Merrill <jason at gcc dot gnu.org> 2011-03-16 20:22:57 UTC ---
Fixed.