Handling of memory errors when creating to-be-closed upvalues
diff --git a/lfunc.c b/lfunc.c
index fde72b8..4f9362f 100644
--- a/lfunc.c
+++ b/lfunc.c
@@ -40,6 +40,7 @@
return c;
}
+
/*
** fill a closure with new closed upvalues
*/
@@ -56,26 +57,20 @@
}
-UpVal *luaF_findupval (lua_State *L, StkId level) {
- UpVal **pp = &L->openupval;
- GCObject *o;
- UpVal *p;
- UpVal *uv;
- lua_assert(isintwups(L) || L->openupval == NULL);
- while ((p = *pp) != NULL && uplevel(p) >= level) {
- if (uplevel(p) == level && !isdead(G(L), p)) /* corresponding upvalue? */
- return p; /* return it */
- pp = &p->u.open.next;
- }
- /* not found: create a new upvalue between 'pp' and 'p' */
- o = luaC_newobj(L, LUA_TUPVAL, sizeof(UpVal));
- uv = gco2upv(o);
- uv->u.open.next = p; /* link it to list of open upvalues */
- uv->u.open.previous = pp;
- if (p)
- p->u.open.previous = &uv->u.open.next;
- *pp = uv;
+/*
+** Create a new upvalue with the given tag 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 tag, StkId level, UpVal **prev) {
+ GCObject *o = luaC_newobj(L, tag, sizeof(UpVal));
+ UpVal *uv = gco2upv(o);
+ UpVal *next = *prev;
uv->v = s2v(level); /* current value lives in the stack */
+ 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;
@@ -84,30 +79,67 @@
}
+/*
+** Find and reuse, or create if it does not exist, a regular 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 */
+ if (uplevel(p) == level && !isdead(G(L), p)) /* corresponding upvalue? */
+ return p; /* return it */
+ pp = &p->u.open.next;
+ }
+ /* not found: create a new upvalue after 'pp' */
+ return newupval(L, LUA_TUPVAL, level, pp);
+}
+
+
static void callclose (lua_State *L, void *ud) {
luaD_callnoyield(L, cast(StkId, ud), 0);
}
-static int closeupval (lua_State *L, UpVal *uv, StkId level, int status) {
- StkId func = level + 1; /* save slot for old error message */
- if (status != LUA_OK) /* was there an error? */
- luaD_seterrorobj(L, status, level); /* save error message */
- else
- setnilvalue(s2v(level));
- if (ttisfunction(uv->v)) { /* object to-be-closed is a function? */
- setobj2s(L, func, uv->v); /* will call it */
- setobjs2s(L, func + 1, level); /* error msg. as argument */
+/*
+** Prepare closing method with its argument for object at
+** index 'func' in the stack. Assume there is an error message
+** (or nil) just below the object.
+*/
+static int prepclosingmethod (lua_State *L, StkId func) {
+ if (ttisfunction(s2v(func))) { /* object to-be-closed is a function? */
+ setobjs2s(L, func + 1, func - 1); /* push error msg. as argument */
}
else { /* try '__close' metamethod */
- const TValue *tm = luaT_gettmbyobj(L, uv->v, TM_CLOSE);
- if (ttisnil(tm))
- return status; /* no metamethod */
+ const TValue *tm = luaT_gettmbyobj(L, s2v(func), TM_CLOSE);
+ if (ttisnil(tm)) /* no metamethod? */
+ return 0; /* nothing to call */
+ setobjs2s(L, func + 1, func); /* 'self' is the argument */
setobj2s(L, func, tm); /* will call metamethod */
- setobj2s(L, func + 1, uv->v); /* with 'self' as argument */
}
L->top = func + 2; /* add function and argument */
- if (status == LUA_OK) /* not in "error mode"? */
+ 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.
+*/
+static int closeupval (lua_State *L, TValue *uv, StkId level, int status) {
+ StkId func = level + 1; /* save slot for old error message */
+ if (unlikely(status != LUA_OK)) /* was there an error? */
+ luaD_seterrorobj(L, status, level); /* save error message */
+ else
+ setnilvalue(s2v(level)); /* no error message */
+ setobj2s(L, func, uv); /* put object on top of error message */
+ if (!prepclosingmethod(L, func))
+ return status; /* nothing to call */
+ if (likely(status == LUA_OK)) /* not in "error mode"? */
callclose(L, func); /* call closing method */
else { /* already inside error handler; cannot raise another error */
int newstatus = luaD_pcall(L, callclose, func, savestack(L, level), 0);
@@ -118,6 +150,36 @@
}
+/*
+** 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, LUA_TUPVALTBC, 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? */
+ StkId func = level + 1;
+ lua_assert(status == LUA_ERRMEM);
+ setobjs2s(L, func, level); /* open space for error message */
+ luaD_seterrorobj(L, status, level); /* save error message */
+ if (prepclosingmethod(L, func))
+ callclose(L, func); /* 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;
@@ -139,7 +201,7 @@
luaC_barrier(L, uv, slot);
if (status >= 0 && uv->tt == LUA_TUPVALTBC) { /* must be closed? */
ptrdiff_t levelrel = savestack(L, level);
- status = closeupval(L, uv, upl, status); /* may reallocate the stack */
+ status = closeupval(L, uv->v, upl, status); /* may reallocate the stack */
level = restorestack(L, levelrel);
}
}
diff --git a/lfunc.h b/lfunc.h
index 4c78800..c9fe131 100644
--- a/lfunc.h
+++ b/lfunc.h
@@ -47,6 +47,7 @@
LUAI_FUNC LClosure *luaF_newLclosure (lua_State *L, int nelems);
LUAI_FUNC void luaF_initupvals (lua_State *L, LClosure *cl);
LUAI_FUNC UpVal *luaF_findupval (lua_State *L, StkId level);
+LUAI_FUNC void luaF_newtbcupval (lua_State *L, StkId level);
LUAI_FUNC int luaF_close (lua_State *L, StkId level, int status);
LUAI_FUNC void luaF_unlinkupval (UpVal *uv);
LUAI_FUNC void luaF_freeproto (lua_State *L, Proto *f);
diff --git a/lvm.c b/lvm.c
index e2994aa..0d82756 100644
--- a/lvm.c
+++ b/lvm.c
@@ -1456,8 +1456,7 @@
vmbreak;
}
vmcase(OP_TBC) {
- UpVal *up = luaF_findupval(L, ra); /* create new upvalue */
- up->tt = LUA_TUPVALTBC; /* mark it to be closed */
+ luaF_newtbcupval(L, ra); /* create new to-be-closed upvalue */
vmbreak;
}
vmcase(OP_JMP) {
diff --git a/testes/locals.lua b/testes/locals.lua
index 8d55e9f..d12c70a 100644
--- a/testes/locals.lua
+++ b/testes/locals.lua
@@ -180,7 +180,7 @@
do
local scoped x = setmetatable({"x"}, {__close = function (self)
a[#a + 1] = self[1] end})
- local scoped y = function () a[#a + 1] = "y" end
+ local scoped y = function (x) assert(x == nil); a[#a + 1] = "y" end
a[#a + 1] = "in"
end
a[#a + 1] = "out"
@@ -210,27 +210,73 @@
and #log == 4)
end
-do
+if rawget(_G, "T") then
+ local function stack(n) n = (n == 0) or stack(n - 1); end;
-- memory error inside closing function
local function foo ()
- local scoped y = function () io.write(2); T.alloccount() end
+ local scoped y = function () T.alloccount() end
local scoped x = setmetatable({}, {__close = function ()
T.alloccount(0); local x = {} -- force a memory error
end})
- io.write("1\n")
error("a") -- common error inside the function's body
end
+ stack(5) -- ensure a minimal number of CI structures
+
+ -- despite memory error, 'y' will be executed and
+ -- memory limit will be lifted
local _, msg = pcall(foo)
-T.alloccount()
assert(msg == "not enough memory")
+ local function close (msg)
+ T.alloccount()
+ assert(msg == "not enough memory")
+ end
+
+ -- set a memory limit and return a closing function to remove the limit
+ local function enter (count)
+ stack(10) -- reserve some stack space
+ T.alloccount(count)
+ return close
+ end
+
+ local function test ()
+ local scoped x = enter(0) -- set a memory limit
+ -- creation of previous upvalue will raise a memory error
+ os.exit(false) -- should not run
+ end
+
+ local _, msg = pcall(test)
+ assert(msg == "not enough memory")
+
+ -- now use metamethod for closing
+ close = setmetatable({}, {__close = function ()
+ T.alloccount()
+ end})
+
+ -- repeat test with extra closing upvalues
+ local function test ()
+ local scoped xxx = function (msg)
+ assert(msg == "not enough memory");
+ error(1000) -- raise another error
+ end
+ local scoped xx = function (msg)
+ assert(msg == "not enough memory");
+ end
+ local scoped x = enter(0) -- set a memory limit
+ -- creation of previous upvalue will raise a memory error
+ os.exit(false) -- should not run
+ end
+
+ local _, msg = pcall(test)
+ assert(msg == 1000)
+
end
-- a suspended coroutine should not close its variables when collected
local co = coroutine.wrap(function()
- local scoped x = function () os.exit(1) end -- should not run
+ local scoped x = function () os.exit(false) end -- should not run
coroutine.yield()
end)
co()
