[Bug c++/83264] New: std::initializer_list with a single element selects the wrong overload

rustamabd at gmail dot com gcc-bugzilla@gcc.gnu.org
Sun Dec 3 20:22:00 GMT 2017


https://gcc.gnu.org/bugzilla/show_bug.cgi?id=83264

            Bug ID: 83264
           Summary: std::initializer_list with a single element selects
                    the wrong overload
           Product: gcc
           Version: 7.2.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: rustamabd at gmail dot com
  Target Milestone: ---

Consider the following:

#include <iostream>
#include <initializer_list>
using namespace std;

template<typename T>
struct A {
  A(int) {
    cout << "A(int)\n";
  }
  A(std::initializer_list<T>) {
    cout << "A(initializer_list)\n";
  }
};

struct UdfInt {
  UdfInt(int) {}
};

int main() {
  A<UdfInt> obj({ 10 });
  return 0;
}

GCC (any version) prints "A(initializer_list)". Other compilers (clang, MSVC)
print "A(int)".

According to [dcl.init.list]/3.9, a single-element braced-init-list should be
unwrapped which means the A(int) overload is the best viable alternative since
the other one needs a user-defined conversion.


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