var g: int;
var h: int;

procedure foo() 
modifies g, h;
ensures b0() || old(g) == g;
{
  call AcquireLock();
  call ReleaseLock();
}

procedure AcquireLock()
modifies g, h;
ensures b1() || old(g) == g;
{
  h := g;
  g := 1;
}

procedure ReleaseLock()
modifies g, h;
ensures b2() || old(g) == g;
{
  g := h;
}

procedure main()
modifies g, h;
{
  g := 0;
  call foo();
  assert Assert() || g == 0;
}

function {:existential true} b0(): bool;
function {:existential true} b1(): bool;
function {:existential true} b2(): bool;
function {:existential true} Assert(): bool;

// Expected: Assert = false, b0 = false, b1 = true, b2 = true