[Bug libstdc++/65942] [5/6 Regression] [C++14] cannot use std::function as comparator in algorithms

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65942

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |rejects-valid
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2015-04-30
            Summary|cannot use std::function as |[5/6 Regression] [C++14]
                   |comparator in algorithms    |cannot use std::function as
                   |                            |comparator in algorithms
     Ever confirmed|0                           |1
           Severity|critical                    |normal

--- Comment #1 from Jonathan Wakely <redi at gcc dot gnu.org> ---
The <experimental/optional> header is not relevant to the bug.

The error only happens in C++14 mode.

#include <algorithm>
#include <functional>

bool cmp1(const int& a, const int& b) { return a < b; }
std::function<bool (const int&, const int&)> cmp2 = cmp1;

int main() {
  int v[1];
  std::sort(v, v, cmp1); // works
  std::sort(v, v, cmp2); // fails
}