where is the memory corruption?

[Jack via Digitalmars-d-learn]

I'm on linux/opensuse, trying to pass a wchar_* from C to D but 
I'm getting only the first letter of that string. Could someone 
help figure out why?

this is the piece of D code:
extern(C) export
void sayHello(const (wchar) *s)
{
        import std.stdio : writeln;
        import std.conv : to;

        import core.runtime : rt_init, rt_term;
        rt_init();
        scope(exit) rt_term();

        writeln("+sayHello()");
        auto s2 = to!string(s);
        writeln("s2 = ", s2);
        writeln("-sayHello()");
}

build with dub, using "targetType": "dynamicLibrary" in dub.json.

and below the piece of C code where I call the lib's function, 
compiled with clang -std=c11 -m64 dll.c -ldl


  const char *libpath = "path/to/library.so";
  void *lh = dlopen(libpath, RTLD_LAZY);
  if(!lh) {
    fprintf(stderr, "dlopen error: %s\n", dlerror());
    return EXIT_FAILURE;
  }

  const wchar_t *s2 = L"hello!";
  void (*fp)(const wchar_t*) = dlsym(lh, "sayHello");
  char *de = dlerror();
  if(de) {
    fprintf(stderr, "slsym error:%s\n", de);
    return EXIT_FAILURE;
  }
  fp(s2);

the output is "h" rather "hello". What am I missing?