[Bug libstdc++/60594] New: std::function of a type with a declared (but not defined) return type fails to compile

[Bug libstdc++/60594] New: std::function of a type with a declared (but not defined) return type fails to compile

[dblaikie at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=60594

            Bug ID: 60594
           Summary: std::function of a type with a declared (but not
                    defined) return type fails to compile
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: libstdc++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: dblaikie at gmail dot com
                CC: chandlerc at gmail dot com

#include <functional>
#include <type_traits>
struct bar;
#if BUG1
struct foo { std::function<bar ()> f; };
#elif BUG2
int i = std::is_copy_constructible<std::function<bar()>>::value;
#else
std::function<bar ()> b;
#endif
struct bar { };
int main() {
  std::function<bar ()> g([] { return bar(); });
}

Clang rejects both BUG1 and BUG2.
GCC ToT (20140219) rejects BUG2.

(I believe the Clang rejection of BUG1 is erroneous and will file a bug for
that)

libc++ with Clang compiles successfully in all 3 variants.

It looks like, somehow, instantiating the declaration of the std::function copy
constructor relies on the completeness of 'bar'.

[Bug libstdc++/60594] std::function of a type with a declared (but not defined) return type fails to compile

[redi at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=60594

--- Comment #1 from Jonathan Wakely <redi at gcc dot gnu.org> ---
Are you sure this is valid? Instantiating std::function (like most std::lib
templates) with an incomplete type is undefined behaviour. Is the function type
bar() complete if bar is not complete?

[Bug libstdc++/60594] std::function of a type with a declared (but not defined) return type fails to compile

[redi at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=60594

--- Comment #2 from Jonathan Wakely <redi at gcc dot gnu.org> ---
> It looks like, somehow, instantiating the declaration of the std::function
> copy constructor relies on the completeness of 'bar'.

I suspect it's not the copy constructor, but that checking for copy
constructibility performs overload resolution, which instantiates the SFINAE
constraint on the function(F&&) constructor, which probably relies on
completeness of the result_type

[Bug libstdc++/60594] std::function of a type with a declared (but not defined) return type fails to compile

[chandlerc at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=60594

--- Comment #3 from Chandler Carruth <chandlerc at gmail dot com> ---
Personally, I've no idea what the standard says.

However, it seems extremely useful to be able to freely use std::function with
return types (and argument types) within the definition those types which is
how this actually started. It also seems reasonable to need to observe whether
the std::function will be copyable (it will) prior to completing it.

Without this, somewhat basic uses if std::function as a member with a
type-erased bit of logic pertaining to the enclosing class with value semantic
interfaces don't work.

[Bug libstdc++/60594] std::function of a type with a declared (but not defined) return type fails to compile

[daniel.kruegler at googlemail dot com]

[-- Warning: decoded text below may be mangled, UTF-8 assumed --]
[-- Attachment #1: Type: text/plain; charset="UTF-8", Size: 4387 bytes --]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=60594

Daniel Krügler <daniel.kruegler at googlemail dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |daniel.kruegler@googlemail.
                   |                            |com

--- Comment #4 from Daniel Krügler <daniel.kruegler at googlemail dot com> ---
(In reply to Jonathan Wakely from comment #1)
> Are you sure this is valid?

I tend to say it is valid, see below for a further comment on this.

> Instantiating std::function (like most std::lib
> templates) with an incomplete type is undefined behaviour. Is the function
> type bar() complete if bar is not complete?

This is definitively true (i.e. bar() is a complete type), because function
types are not affected by the definition of complete types, 3.9 p. says:

"Incompletely defined object types and the void types are incomplete types
(3.9.1)."

I would say that the definition of "INVOKE(f, t1, t2, ..., tN, R)" is not
well-defined for incomplete R (except when R==void) due to the
"implicitly-convertible" constraint mentioned in 20.9.2 p2, but 20.9.11 doesn't
seem to impose this constraint to hold when instantiating a std::function<>. On
the other hand the current std::function wording clearly is underspecified:
There are several members that would require R to be a complete type. I don't
think that the default constructor is one of these, though. Among the members
where this is needed is IMO

template<class F> function(F f);

because the compile-time constraint

"unless f is Callable (20.9.11.2) for argument types ArgTypes... and return
type R."

can only be deduced, if R is complete (modulo void again).
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From: "patnel97269-gfortran at yahoo dot fr" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug fortran/60596] New: Inquire size for stream zero
Date: Wed, 19 Mar 2014 21:30:00 -0000
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http://gcc.gnu.org/bugzilla/show_bug.cgi?id`596

            Bug ID: 60596
           Summary: Inquire size for stream zero
           Product: gcc
           Version: 4.8.2
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: fortran
          Assignee: unassigned at gcc dot gnu.org
          Reporter: patnel97269-gfortran at yahoo dot fr

Created attachment 32398
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id2398&actioníit
program

Hi all,

When calling inquire for a stream size, the size is reported to be zero.

In the intel fortran compiler the sizer is correctly reported.

I attached a small program, and the necessary input file.


Use that as < input :
>ONE Homo sapiens alu


Thanks.

[Bug libstdc++/60594] std::function of a type with a declared (but not defined) return type fails to compile

[kariya_mitsuru at hotmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=60594

Mitsuru Kariya <kariya_mitsuru at hotmail dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |kariya_mitsuru at hotmail dot com

--- Comment #5 from Mitsuru Kariya <kariya_mitsuru at hotmail dot com> ---
FYI, the BUG2 above is compiled successfully by gcc 4.7.3.

cf. http://melpon.org/wandbox/permlink/UZdP4fovs2ATM2iZ


Additionally, the sample code below cannot be compiled by gcc HEAD.

#include <functional>

struct S {
    std::function<S()> f;
};

int main()
{
    S l{ []{ return S{nullptr}; } };
}

cf. http://melpon.org/wandbox/permlink/HAZ7i5JE94KSQhM7


It is also compiled successfully by gcc 4.7.3.
And I think that struct S is not incomplete type (at least, at the point where
it is used).

[Bug libstdc++/60594] std::function of a type with a declared (but not defined) return type fails to compile

[redi at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=60594

--- Comment #6 from Jonathan Wakely <redi at gcc dot gnu.org> ---
(In reply to Mitsuru Kariya from comment #5)
> FYI, the BUG2 above is compiled successfully by gcc 4.7.3.

Yes, but std::function in 4.7.3 fails other, more important tests.

[Bug libstdc++/60594] [4.8/4.9/4.10 Regression] std::function of a type with a declared (but not defined) return type fails to compile

[redi at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=60594

--- Comment #8 from Jonathan Wakely <redi at gcc dot gnu.org> ---
Author: redi
Date: Tue Apr 15 15:25:52 2014
New Revision: 209422

URL: http://gcc.gnu.org/viewcvs?rev=209422&root=gcc&view=rev
Log:
    PR libstdc++/60594
    * include/std/functional (function::_Callable): Exclude own type
    from the callable checks.
    * testsuite/20_util/function/60594.cc: New.

Added:
    trunk/libstdc++-v3/testsuite/20_util/function/60594.cc
Modified:
    trunk/libstdc++-v3/ChangeLog
    trunk/libstdc++-v3/include/std/functional

[Bug libstdc++/60594] [4.8/4.9 Regression] std::function of a type with a declared (but not defined) return type fails to compile

[redi at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=60594

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
      Known to work|                            |4.10.0
            Summary|[4.8/4.9/4.10 Regression]   |[4.8/4.9 Regression]
                   |std::function of a type     |std::function of a type
                   |with a declared (but not    |with a declared (but not
                   |defined) return type fails  |defined) return type fails
                   |to compile                  |to compile

--- Comment #9 from Jonathan Wakely <redi at gcc dot gnu.org> ---
Fixed on trunk so far

[Bug libstdc++/60594] [4.8/4.9 Regression] std::function of a type with a declared (but not defined) return type fails to compile

[redi at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=60594

--- Comment #10 from Jonathan Wakely <redi at gcc dot gnu.org> ---
Author: redi
Date: Tue May  6 11:45:14 2014
New Revision: 210103

URL: http://gcc.gnu.org/viewcvs?rev=210103&root=gcc&view=rev
Log:
Backport libstdc++/60594 fix from mainline.

    PR libstdc++/60594
    * include/std/functional (function::_Callable): Exclude own type
    from the callable checks.
    * testsuite/20_util/function/60594.cc: New.

Added:
    branches/gcc-4_9-branch/libstdc++-v3/testsuite/20_util/function/60594.cc
Modified:
    branches/gcc-4_9-branch/libstdc++-v3/ChangeLog
    branches/gcc-4_9-branch/libstdc++-v3/include/std/functional

[Bug libstdc++/60594] [4.8/4.9 Regression] std::function of a type with a declared (but not defined) return type fails to compile

[redi at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=60594

--- Comment #11 from Jonathan Wakely <redi at gcc dot gnu.org> ---
Author: redi
Date: Tue May  6 13:27:46 2014
New Revision: 210105

URL: http://gcc.gnu.org/viewcvs?rev=210105&root=gcc&view=rev
Log:
Backport libstdc++/60594 fix from mainline.

    PR libstdc++/60594
    * include/std/functional (function::_Callable): Exclude own type
    from the callable checks.
    * testsuite/20_util/function/60594.cc: New.

Added:
    branches/gcc-4_8-branch/libstdc++-v3/testsuite/20_util/function/60594.cc
Modified:
    branches/gcc-4_8-branch/libstdc++-v3/ChangeLog
    branches/gcc-4_8-branch/libstdc++-v3/include/std/functional

[Bug libstdc++/60594] [4.8/4.9 Regression] std::function of a type with a declared (but not defined) return type fails to compile

[redi at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=60594

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|ASSIGNED                    |RESOLVED
         Resolution|---                         |FIXED
      Known to fail|                            |4.8.2, 4.9.0

--- Comment #12 from Jonathan Wakely <redi at gcc dot gnu.org> ---
Fixed for 4.8.3 and 4.9.1