Crash when including C code into mirageos

Ecosystem
1

I have problem described in https://github.com/mirage/mirage-skeleton/issues/251.
Addition of trivial C code work when compiling mirageOS for unix platform, but crashes when compiled and run as Xen VM. Example C code:

void read_int_real(int aa)
{
    asm(""); // will prevent optimization (e.g. removing whole function)?
    aa =  aa*2;
}

CAMLprim value read_int(value aa)
{
    CAMLparam1(aa);
    read_int_real(Int_val(aa));
    CAMLreturn(Val_unit);
}

Called as in

let bb = (read_int aa; 33) in
...

Any hint what is the cause?

2

Building same code in ubuntu 14.04 - it works on Xen too. The VM image compiled on ubuntu 16.04 - crash.