Assert in VM

["Nick Trout" <nick@...>]

What does it mean when this assertion fails in the VM? (I chopped it up
for clarity)

          lua_assert(ci->u.l.pc == &pc);

I assume this is bad, something like the function returning is trying to
return to a different place in the previous frame? This is a coroutine
BTW.

--nick




    case OP_RETURN: {
        CallInfo *ci = L->ci - 1;  /* previous function frame */
        int b = GETARG_B(i);
        if (b != 0) L->top = ra+b-1;
        lua_assert(L->ci->state & CI_HASFRAME);
        if (L->openupval) luaF_close(L, base);
        L->ci->state = CI_SAVEDPC;  /* deactivate current function */
        L->ci->u.l.savedpc = pc;
        /* previous function was running `here'? */
        if (!(ci->state & CI_CALLING)) {
          lua_assert((ci->state & CI_C) || ci->u.l.pc != &pc);
          return ra;  /* no: return */
        }
        else {  /* yes: continue its execution */
          int nresults;
          lua_assert(ci->u.l.pc == &pc);
          lua_assert(ttisfunction(ci->base - 1));
          lua_assert(ci->state & CI_SAVEDPC);
          lua_assert(GET_OPCODE(*(ci->u.l.savedpc - 1)) == OP_CALL);
          nresults = GETARG_C(*(ci->u.l.savedpc - 1)) - 1;
          luaD_poscall(L, nresults, ra);
          if (nresults >= 0) L->top = L->ci->top;
          goto retentry;
        }
      }