[Bug libstdc++/67617] New: Non-standard const requirements imposed on associate container comparison objects

[Bug libstdc++/67617] New: Non-standard const requirements imposed on associate container comparison objects

[mdempsky at google dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67617

            Bug ID: 67617
           Summary: Non-standard const requirements imposed on associate
                    container comparison objects
           Product: gcc
           Version: 4.8.4
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: libstdc++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: mdempsky at google dot com
  Target Milestone: ---

This code appears to me to be conforming to the C++ standard, but it's rejected
by G++/libstdc++:

    #include <set>
    struct compare {
      bool operator()(int a, int b);
    };
    void func() {
      const std::set<int, compare> s;
      s.find(0);
    }

because compare::operator() is not const qualified.

N3690 [associative.reqmts]p2 says "The object of type Compare is called the
comparison object of the container", and p3 talks about the requirements on
behavior of a comparison object comp.  However, none of the requirements seem
to impose requirements on objects of type const Compare.

[Bug libstdc++/67617] Non-standard const requirements imposed on associative container comparison objects

[daniel.kruegler at googlemail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67617

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

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

--- Comment #3 from Daniel Krügler <daniel.kruegler at googlemail dot com> ---
(In reply to Jonathan Wakely from comment #1)
> If that code is conforming then it's a defect in the standard.

I agree. I believe the wording for associative containers is not as clear as it
should be. For unordered containers 23.2.5 p11 speaks of "possibly const value"
for hasher and binary predicate, but in 23.2.4 p8 this additional "possibly
const" requirement is missing. I'm submitting an LWG issue for this and provide
the issue number once available.
>From gcc-bugs-return-498098-listarch-gcc-bugs=gcc.gnu.org@gcc.gnu.org Sat Sep 26 17:53:01 2015
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Subject: [Bug fortran/67567] resolve.c: gfc_error called with iface->module == NULL
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https://gcc.gnu.org/bugzilla/show_bug.cgi?idg567

--- Comment #7 from Paul Thomas <pault at gcc dot gnu.org> ---
Author: pault
Date: Sat Sep 26 17:52:24 2015
New Revision: 228169

URL: https://gcc.gnu.org/viewcvs?rev"8169&root=gcc&view=rev
Log:
2013-09-26  Paul Thomas  <pault@gcc.gnu.org>

        PR fortran/67567
        * resolve.c (resolve_fl_procedure): For module procedures, take
        the parent module name and the submodule name from the name of
        the namespace.

Modified:
    trunk/gcc/fortran/ChangeLog
    trunk/gcc/fortran/resolve.c

[Bug libstdc++/67617] Non-standard const requirements imposed on associative container comparison objects

[daniel.kruegler at googlemail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67617

--- Comment #4 from Daniel Krügler <daniel.kruegler at googlemail dot com> ---
(In reply to Jonathan Wakely from comment #2)
> Both Clang/libc++ and MSVC/Dinkumware reject it for the same reason.

I notice that the Dinkumware version associated with Visual Studio 2015 accepts
the code.
>From gcc-bugs-return-498101-listarch-gcc-bugs=gcc.gnu.org@gcc.gnu.org Sat Sep 26 18:27:03 2015
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Subject: [Bug c++/67319] Short-hand concepts for variadic member functions broken
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https://gcc.gnu.org/bugzilla/show_bug.cgi?idg319

--- Comment #1 from Roland B <rbock at eudoxos dot de> ---
Using the terse notation works fine, btw:


// -----------------------------
template <typename T>
concept bool Any()
{
  return true;
}

struct my_struct
{
  auto sample(Any... args) -> void;
};

int main()
{
  my_struct{}.sample();
}
// -------------------------------

[Bug libstdc++/67617] Non-standard const requirements imposed on associative container comparison objects

[daniel.kruegler at googlemail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67617

--- Comment #6 from Daniel Krügler <daniel.kruegler at googlemail dot com> ---
(In reply to Daniel Krügler from comment #4)
> (In reply to Jonathan Wakely from comment #2)
> > Both Clang/libc++ and MSVC/Dinkumware reject it for the same reason.
> 
> I notice that the Dinkumware version associated with Visual Studio 2015
> accepts the code.

... assuming a proper definition of the operator() overload is provided,
of-course.
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To: gcc-bugs@gcc.gnu.org
Subject: [Bug c++/67727] New: [concepts] parameterized constraint not being checked for unused variables
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https://gcc.gnu.org/bugzilla/show_bug.cgi?idg727

            Bug ID: 67727
           Summary: [concepts] parameterized constraint not being checked
                    for unused variables
           Product: gcc
           Version: 6.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: ryan.burn at gmail dot com
  Target Milestone: ---

The following code prints 1 1, but according to

http://stackoverflow.com/questions/32801326/in-requires-parameter-lists-can-you-introduce-types-that-result-in-substitution

should print 1 0

/////////////////////////////////////////////////////////////////////////
#include <iterator>
#include <iostream>

template <class Iter>
concept bool Iterator     requires(Iter i, typename std::iterator_traits<Iter>::value_type val,
             typename std::iterator_traits<Iter>::reference ref) {
  ++i;
};

int main() {
  std::cout << Iterator<int*> << "\n"; // prints 1
  std::cout << Iterator<int> << "\n"; // prints 1
  return 0;
}
/////////////////////////////////////////////////////////////////////////

[Bug libstdc++/67617] [DR 2542] Non-standard const requirements imposed on associative container comparison objects

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67617

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |SUSPENDED
   Last reconfirmed|                            |2015-09-27
            Summary|Non-standard const          |[DR 2542] Non-standard
                   |requirements imposed on     |const requirements imposed
                   |associative container       |on associative container
                   |comparison objects          |comparison objects
     Ever confirmed|0                           |1