[Bug c++/48562] [C++0x] warn about uses of initializer_list that will lead to dangling pointers

[fw at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=48562

Florian Weimer <fw at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |fw at gcc dot gnu.org
           See Also|                            |https://gcc.gnu.org/bugzill
                   |                            |a/show_bug.cgi?id=66476

--- Comment #8 from Florian Weimer <fw at gcc dot gnu.org> ---
It would also mention to warn about std::initializer_list references in
function arguments, I think.  We received a downstream bug report:

#include <initializer_list>
#include <iostream>

template <typename T> class ArrayRef {
public:
  using size_type = size_t;

private:
  /// The start of the array, in an external buffer.
  const T *Data = nullptr;

  /// The number of elements.
  size_type Length = 0;

public:
  /// Construct an ArrayRef from a std::initializer_list.
  /*implicit*/ ArrayRef(const std::initializer_list<T> &Vec)
      : Data(Vec.begin() == Vec.end() ? (T *)nullptr : Vec.begin()),
        Length(Vec.size()) {}

  const T &operator[](size_t Index) const { return Data[Index]; }
};

int main(int argc, char **argv) {
  const ArrayRef<int> Foo = {42};
  std::cout << "Foo " << Foo[0] << "\n";
  return 0;
}

https://bugzilla.redhat.com/show_bug.cgi?id=1561373

I believe this code is buggy, and it would be nice to warn about this.  Almost
any std::initializer_list object will be a temporary, after all, and the called
function should move the initializer elements, not copy them.