lua/lfunc.c
Roberto Ierusalimschy 9e6807c3c9 Do not collect open upvalues
Open upvalues are kept alive together with their corresponding
stack. This change makes a simpler and safer fix to the issue in
commit 440a5ee78c, about upvalues in the list of open upvalues
being collected while others are being created. (That previous fix
may not be correct.)
2019-07-22 09:41:10 -03:00

281 lines
8.2 KiB
C

/*
** $Id: lfunc.c $
** Auxiliary functions to manipulate prototypes and closures
** See Copyright Notice in lua.h
*/
#define lfunc_c
#define LUA_CORE
#include "lprefix.h"
#include <stddef.h>
#include "lua.h"
#include "ldebug.h"
#include "ldo.h"
#include "lfunc.h"
#include "lgc.h"
#include "lmem.h"
#include "lobject.h"
#include "lstate.h"
CClosure *luaF_newCclosure (lua_State *L, int n) {
GCObject *o = luaC_newobj(L, LUA_TCCL, sizeCclosure(n));
CClosure *c = gco2ccl(o);
c->nupvalues = cast_byte(n);
return c;
}
LClosure *luaF_newLclosure (lua_State *L, int n) {
GCObject *o = luaC_newobj(L, LUA_TLCL, sizeLclosure(n));
LClosure *c = gco2lcl(o);
c->p = NULL;
c->nupvalues = cast_byte(n);
while (n--) c->upvals[n] = NULL;
return c;
}
/*
** fill a closure with new closed upvalues
*/
void luaF_initupvals (lua_State *L, LClosure *cl) {
int i;
for (i = 0; i < cl->nupvalues; i++) {
GCObject *o = luaC_newobj(L, LUA_TUPVAL, sizeof(UpVal));
UpVal *uv = gco2upv(o);
uv->v = &uv->u.value; /* make it closed */
setnilvalue(uv->v);
cl->upvals[i] = uv;
luaC_objbarrier(L, cl, o);
}
}
/*
** Create a new upvalue at the given level, and link it to the list of
** open upvalues of 'L' after entry 'prev'.
**/
static UpVal *newupval (lua_State *L, int tbc, StkId level, UpVal **prev) {
GCObject *o = luaC_newobj(L, LUA_TUPVAL, sizeof(UpVal));
UpVal *uv = gco2upv(o);
UpVal *next = *prev;
uv->v = s2v(level); /* current value lives in the stack */
uv->tbc = tbc;
uv->u.open.next = next; /* link it to list of open upvalues */
uv->u.open.previous = prev;
if (next)
next->u.open.previous = &uv->u.open.next;
*prev = uv;
if (!isintwups(L)) { /* thread not in list of threads with upvalues? */
L->twups = G(L)->twups; /* link it to the list */
G(L)->twups = L;
}
return uv;
}
/*
** Find and reuse, or create if it does not exist, an upvalue
** at the given level.
*/
UpVal *luaF_findupval (lua_State *L, StkId level) {
UpVal **pp = &L->openupval;
UpVal *p;
lua_assert(isintwups(L) || L->openupval == NULL);
while ((p = *pp) != NULL && uplevel(p) >= level) { /* search for it */
lua_assert(!isdead(G(L), p));
if (uplevel(p) == level) /* corresponding upvalue? */
return p; /* return it */
pp = &p->u.open.next;
}
/* not found: create a new upvalue after 'pp' */
return newupval(L, 0, level, pp);
}
static void callclose (lua_State *L, void *ud) {
UNUSED(ud);
luaD_callnoyield(L, L->top - 3, 0);
}
/*
** Prepare closing method plus its arguments for object 'obj' with
** error message 'err'. (This function assumes EXTRA_STACK.)
*/
static int prepclosingmethod (lua_State *L, TValue *obj, TValue *err) {
StkId top = L->top;
const TValue *tm = luaT_gettmbyobj(L, obj, TM_CLOSE);
if (ttisnil(tm)) /* no metamethod? */
return 0; /* nothing to call */
setobj2s(L, top, tm); /* will call metamethod... */
setobj2s(L, top + 1, obj); /* with 'self' as the 1st argument */
setobj2s(L, top + 2, err); /* and error msg. as 2nd argument */
L->top = top + 3; /* add function and arguments */
return 1;
}
/*
** Prepare and call a closing method. If status is OK, code is still
** inside the original protected call, and so any error will be handled
** there. Otherwise, a previous error already activated original
** protected call, and so the call to the closing method must be
** protected here. (A status = CLOSEPROTECT behaves like a previous
** error, to also run the closing method in protected mode).
** If status is OK, the call to the closing method will be pushed
** at the top of the stack. Otherwise, values are pushed after
** the 'level' of the upvalue being closed, as everything after
** that won't be used again.
*/
static int callclosemth (lua_State *L, StkId level, int status) {
TValue *uv = s2v(level); /* value being closed */
if (likely(status == LUA_OK)) {
if (prepclosingmethod(L, uv, &G(L)->nilvalue)) /* something to call? */
callclose(L, NULL); /* call closing method */
else if (!ttisnil(uv)) { /* non-closable non-nil value? */
int idx = cast_int(level - L->ci->func);
const char *vname = luaG_findlocal(L, L->ci, idx, NULL);
if (vname == NULL) vname = "?";
luaG_runerror(L, "attempt to close non-closable variable '%s'", vname);
}
}
else { /* must close the object in protected mode */
ptrdiff_t oldtop;
level++; /* space for error message */
oldtop = savestack(L, level + 1); /* top will be after that */
luaD_seterrorobj(L, status, level); /* set error message */
if (prepclosingmethod(L, uv, s2v(level))) { /* something to call? */
int newstatus = luaD_pcall(L, callclose, NULL, oldtop, 0);
if (newstatus != LUA_OK && status == CLOSEPROTECT) /* first error? */
status = newstatus; /* this will be the new error */
else /* leave original error (or nil) on top */
L->top = restorestack(L, oldtop);
}
/* else no metamethod; ignore this case and keep original error */
}
return status;
}
/*
** Try to create a to-be-closed upvalue
** (can raise a memory-allocation error)
*/
static void trynewtbcupval (lua_State *L, void *ud) {
StkId level = cast(StkId, ud);
lua_assert(L->openupval == NULL || uplevel(L->openupval) < level);
newupval(L, 1, level, &L->openupval);
}
/*
** Create a to-be-closed upvalue. If there is a memory error
** when creating the upvalue, the closing method must be called here,
** as there is no upvalue to call it later.
*/
void luaF_newtbcupval (lua_State *L, StkId level) {
int status = luaD_rawrunprotected(L, trynewtbcupval, level);
if (unlikely(status != LUA_OK)) { /* memory error creating upvalue? */
lua_assert(status == LUA_ERRMEM);
luaD_seterrorobj(L, LUA_ERRMEM, level + 1); /* save error message */
if (prepclosingmethod(L, s2v(level), s2v(level + 1)))
callclose(L, NULL); /* call closing method */
luaD_throw(L, LUA_ERRMEM); /* throw memory error */
}
}
void luaF_unlinkupval (UpVal *uv) {
lua_assert(upisopen(uv));
*uv->u.open.previous = uv->u.open.next;
if (uv->u.open.next)
uv->u.open.next->u.open.previous = uv->u.open.previous;
}
int luaF_close (lua_State *L, StkId level, int status) {
UpVal *uv;
while ((uv = L->openupval) != NULL && uplevel(uv) >= level) {
TValue *slot = &uv->u.value; /* new position for value */
lua_assert(uplevel(uv) < L->top);
if (uv->tbc && status != NOCLOSINGMETH) {
/* must run closing method, which may change the stack */
ptrdiff_t levelrel = savestack(L, level);
status = callclosemth(L, uplevel(uv), status);
level = restorestack(L, levelrel);
}
luaF_unlinkupval(uv);
setobj(L, slot, uv->v); /* move value to upvalue slot */
uv->v = slot; /* now current value lives here */
if (!iswhite(uv))
gray2black(uv); /* closed upvalues cannot be gray */
luaC_barrier(L, uv, slot);
}
return status;
}
Proto *luaF_newproto (lua_State *L) {
GCObject *o = luaC_newobj(L, LUA_TPROTO, sizeof(Proto));
Proto *f = gco2p(o);
f->k = NULL;
f->sizek = 0;
f->p = NULL;
f->sizep = 0;
f->code = NULL;
f->sizecode = 0;
f->lineinfo = NULL;
f->sizelineinfo = 0;
f->abslineinfo = NULL;
f->sizeabslineinfo = 0;
f->upvalues = NULL;
f->sizeupvalues = 0;
f->numparams = 0;
f->is_vararg = 0;
f->maxstacksize = 0;
f->locvars = NULL;
f->sizelocvars = 0;
f->linedefined = 0;
f->lastlinedefined = 0;
f->source = NULL;
return f;
}
void luaF_freeproto (lua_State *L, Proto *f) {
luaM_freearray(L, f->code, f->sizecode);
luaM_freearray(L, f->p, f->sizep);
luaM_freearray(L, f->k, f->sizek);
luaM_freearray(L, f->lineinfo, f->sizelineinfo);
luaM_freearray(L, f->abslineinfo, f->sizeabslineinfo);
luaM_freearray(L, f->locvars, f->sizelocvars);
luaM_freearray(L, f->upvalues, f->sizeupvalues);
luaM_free(L, f);
}
/*
** Look for n-th local variable at line 'line' in function 'func'.
** Returns NULL if not found.
*/
const char *luaF_getlocalname (const Proto *f, int local_number, int pc) {
int i;
for (i = 0; i<f->sizelocvars && f->locvars[i].startpc <= pc; i++) {
if (pc < f->locvars[i].endpc) { /* is variable active? */
local_number--;
if (local_number == 0)
return getstr(f->locvars[i].varname);
}
}
return NULL; /* not found */
}