/* Upvalues are tricky. Here's why.
*
* A particular upvalue may be either "open", in which case its member v
* points into a thread's stack, or "closed" in which case it points to the
* upvalue itself. An upvalue is closed under any of the following conditions:
* -- The function that initially declared the variable "local" returns
* -- The thread in which the closure was created is garbage collected
*
* To make things wackier, just because a thread is reachable by Lua doesn't
* mean it's in our root set. We need to be able to treat an open upvalue
* from an unreachable thread as a closed upvalue.
*
* The solution:
* (a) For the purposes of persisting, don't indicate whether an upvalue is
* closed or not.
* (b) When unpersisting, pretend that all upvalues are closed.
* (c) When persisting, persist all open upvalues referenced by a thread
* that is persisted, and tag each one with the corresponding stack position
* (d) When unpersisting, "reopen" each of these upvalues as the thread is
* unpersisted
*/
static void persistupval(PersistInfo *pi) {
/* perms reftbl ... upval */
UpVal *uv = toupval(pi->L, -1);
luaA_pushobject(pi->L, uv->v);
/* perms reftbl ... upval obj */
persist(pi);
lua_pop(pi->L, 1);
/* perms reftbl ... upval */
}
/* The GC is not fond of finding upvalues in tables. We get around this
* during persistence using a weakly keyed table, so that the GC doesn't
* bother to mark them. This won't work in unpersisting, however, since
* if we make the values weak they'll be collected (since nothing else
* references them). Our solution, during unpersisting, is to represent
* upvalues as dummy functions, each with one upvalue. */
static void boxupval(lua_State *L) {
/* ... upval */
LClosure *lcl;
UpVal *uv;
uv = toupval(L, -1);
lua_pop(L, 1);
/* ... */
lcl = (LClosure*)luaF_newLclosure(L, 1, &L->_gt);
pushclosure(L, (Closure*)lcl);
/* ... func */
lcl->p = makefakeproto(L, 1);
lcl->upvals[0] = uv;
}
/* Upvalues are tricky. Here's why.
*
* A particular upvalue may be either "open", in which case its member v
* points into a thread's stack, or "closed" in which case it points to the
* upvalue itself. An upvalue is closed under any of the following conditions:
* -- The function that initially declared the variable "local" returns
* -- The thread in which the closure was created is garbage collected
*
* To make things wackier, just because a thread is reachable by Lua doesn't
* mean it's in our root set. We need to be able to treat an open upvalue
* from an unreachable thread as a closed upvalue.
*
* The solution:
* (a) For the purposes of persisting, don't indicate whether an upvalue is
* closed or not.
* (b) When unpersisting, pretend that all upvalues are closed.
* (c) When persisting, persist all open upvalues referenced by a thread
* that is persisted, and tag each one with the corresponding stack position
* (d) When unpersisting, "reopen" each of these upvalues as the thread is
* unpersisted
*/
static void persistupval(PersistInfo *pi)
{
/* perms reftbl ... upval */
UpVal *uv = toupval(pi->L, -1);
lua_checkstack(pi->L, 1);
/* We can't permit the upval to linger around on the stack, as Lua
* will bail if its GC finds it. */
lua_pop(pi->L, 1);
/* perms reftbl ... */
LIF(A,pushobject)(pi->L, uv->v);
/* perms reftbl ... obj */
persist(pi);
/* perms reftbl ... obj */
}
static void unpersistfunction(int ref, UnpersistInfo *upi) {
/* perms reftbl ... */
LClosure *lcl;
int i;
lu_byte nupvalues;
verify(luaZ_read(&upi->zio, &nupvalues, sizeof(lu_byte)) == 0);
lcl = (LClosure*)luaF_newLclosure(upi->L, nupvalues, &upi->L->_gt);
pushclosure(upi->L, (Closure*)lcl);
/* perms reftbl ... func */
/* Put *some* proto in the closure, before the GC can find it */
lcl->p = makefakeproto(upi->L, nupvalues);
/* Also, we need to temporarily fill the upvalues */
lua_pushnil(upi->L);
/* perms reftbl ... func nil */
for(i=0; i<nupvalues; i++) {
lcl->upvals[i] = makeupval(upi->L, -1);
}
lua_pop(upi->L, 1);
/* perms reftbl ... func */
/* I can't see offhand how a function would ever get to be self-
* referential, but just in case let's register it early */
registerobject(ref, upi);
/* Now that it's safe, we can get the real proto */
unpersist(upi);
/* perms reftbl ... func proto? */
lua_assert(lua_type(upi->L, -1) == LUA_TPROTO);
/* perms reftbl ... func proto */
lcl->p = toproto(upi->L, -1);
lua_pop(upi->L, 1);
/* perms reftbl ... func */
for(i=0; i<nupvalues; i++) {
/* perms reftbl ... func */
unpersist(upi);
/* perms reftbl ... func func2 */
unboxupval(upi->L);
/* perms reftbl ... func upval */
lcl->upvals[i] = toupval(upi->L, -1);
lua_pop(upi->L, 1);
/* perms reftbl ... func */
}
/* perms reftbl ... func */
/* Finally, the fenv */
unpersist(upi);
/* perms reftbl ... func fenv/nil? */
lua_assert(lua_type(upi->L, -1) == LUA_TNIL ||
lua_type(upi->L, -1) == LUA_TTABLE);
/* perms reftbl ... func fenv/nil */
if(!lua_isnil(upi->L, -1)) {
/* perms reftbl ... func fenv */
lua_setfenv(upi->L, -2);
/* perms reftbl ... func */
} else {
/* perms reftbl ... func nil */
lua_pop(upi->L, 1);
/* perms reftbl ... func */
}
/* perms reftbl ... func */
}
static void unpersistthread(int ref, UnpersistInfo *upi) {
/* perms reftbl ... */
lua_State *L2;
L2 = lua_newthread(upi->L);
/* L1: perms reftbl ... thr */
/* L2: (empty) */
registerobject(ref, upi);
/* First, deserialize the object stack. */
{
int i, stacksize;
verify(luaZ_read(&upi->zio, &stacksize, sizeof(int)) == 0);
luaD_growstack(L2, stacksize);
/* Make sure that the first stack element (a nil, representing
* the imaginary top-level C function) is written to the very,
* very bottom of the stack */
L2->top--;
for(i=0; i<stacksize; i++) {
unpersist(upi);
/* L1: perms reftbl ... thr obj* */
}
lua_xmove(upi->L, L2, stacksize);
/* L1: perms reftbl ... thr */
/* L2: obj* */
}
/* Now, deserialize the CallInfo stack. */
{
int i, numframes;
verify(luaZ_read(&upi->zio, &numframes, sizeof(int)) == 0);
luaD_reallocCI(L2,numframes*2);
for(i=0; i<numframes; i++) {
CallInfo *ci = L2->base_ci + i;
int stackbase, stacktop, pc;
verify(luaZ_read(&upi->zio, &stackbase, sizeof(int)) == 0);
verify(luaZ_read(&upi->zio, &stacktop, sizeof(int)) == 0);
verify(luaZ_read(&upi->zio, &pc, sizeof(int)) == 0);
verify(luaZ_read(&upi->zio, &(ci->state), sizeof(int)) == 0);
ci->base = L2->stack+stackbase;
ci->top = L2->stack+stacktop;
if(!(ci->state & CI_C)) {
ci->u.l.savedpc = ci_func(ci)->l.p->code + pc;
}
ci->u.l.tailcalls = 0;
/* Update the pointer each time, to keep the GC
* happy*/
L2->ci = ci;
}
}
/* L1: perms reftbl ... thr */
{
int stackbase, stacktop;
verify(luaZ_read(&upi->zio, &stackbase, sizeof(int)) == 0);
verify(luaZ_read(&upi->zio, &stacktop, sizeof(int)) == 0);
L2->base = L2->stack + stackbase;
L2->top = L2->stack + stacktop;
}
/* Finally, "reopen" upvalues (see persistupval() for why) */
{
UpVal* uv;
GCObject **nextslot = &L2->openupval;
while(1) {
int stackpos;
unpersist(upi);
/* perms reftbl ... thr uv/nil */
if(lua_isnil(upi->L, -1)) {
/* perms reftbl ... thr nil */
lua_pop(upi->L, 1);
/* perms reftbl ... thr */
break;
}
/* perms reftbl ... thr boxeduv */
unboxupval(upi->L);
/* perms reftbl ... thr uv */
uv = toupval(upi->L, -1);
lua_pop(upi->L, 1);
/* perms reftbl ... thr */
verify(luaZ_read(&upi->zio, &stackpos, sizeof(int)) == 0);
uv->v = L2->stack + stackpos;
gcunlink(upi->L, valtogco(uv));
uv->marked = 1;
*nextslot = valtogco(uv);
nextslot = &uv->next;
}
*nextslot = NULL;
}
}
