Is initializer list like this legal in C++11?

Question

I read the C++ primer 5th edition, which says that newest standard support list initializer.

My test code is like this:

#include <iostream>
#include <string>
#include <cctype>
#include <vector>
using std::cin;
using std::cout;
using std::endl;
using std::string;
using std::vector;
using std::ispunct;
int main(int argc, char *argv[])
{
    vector<int> a1 = {0,1,2};
    vector<int> a2{0,1,2}; // should be equal to a1
    return 0;
}

Then I use Clang 4.0:

bash-3.2$ c++ --version
Apple clang version 4.0 (tags/Apple/clang-421.0.60) (based on LLVM 3.1svn)
Target: x86_64-apple-darwin12.2.0
Thread model: posix

And compile it like this:

c++ -std=c++11 -Wall    playground.cc   -o playground

However, it complains like this:

playground.cc:13:17: error: no matching constructor for initialization of
      'vector<int>'
    vector<int> a1 = {0,1,2};
                ^    ~~~~~~~

 /usr/include/c++/4.2.1/bits/stl_vector.h:255:9: note: candidate constructor
  [with _InputIterator = int] not viable: no known conversion from 'int'
  to 'const allocator_type' (aka 'const std::allocator<int>') for 3rd
  argument;
    vector(_InputIterator __first, _InputIterator __last,
    ^
/usr/include/c++/4.2.1/bits/stl_vector.h:213:7: note: candidate constructor
  not viable: no known conversion from 'int' to 'const allocator_type'
  (aka 'const std::allocator<int>') for 3rd argument;
  vector(size_type __n, const value_type& __value = value_type(),

I checked the C++ support status of Clang , and it looks that it should already support Initializer lists in Clang 3.1. But why does my codes doesn't work. Does anyone have ideas about this?

Answer 1

The code is legal, the problem is with your compiler+stdlib setup.

Apple's Xcode ships with the ancient version 4.2.1 of the GNU C++ standard library, libstdc++ (see https://stackoverflow.com/a/14150421/981959 for details) and that version pre-dates C++11 by many years so its std::vector doesn't have an initializer-list constructor.

To use C++11 features you either need to install and use a newer libstdc++, or tell clang to use Apple's own libc++ library, which you do with the -stdlib=libc++ option.