cannot inspect vector<string>

Debugging the following simple program

#include <string>
#include <vector>
using namespace std;

int main(int argc, char *argv[])
{
    string str = "Hello World!";
    vector<string> vec{str};
    return 0;
}

CMakeLists.txt

project(debug)
SET(CMAKE_CXX_STANDARD 11)
add_executable(debug "main.cpp")

does not show the contents of vec:
vec <notaccessible> vector<string>

while when building with GCC the contents are shown
vec <1 items> vector<string>

Load system GDB pretty printers is disabled (otherwise it would not work at all).

The problem does not occur with std::array, std::list and not with other element types (e.g. int, custom classes)