New API function 'lua_closeslot'
Closing a to-be-closed variable with 'lua_settop' is too restrictive,
as it erases all slots above the variable. Moreover, it adds side
effects to 'lua_settop', which should be a fairly basic function.
diff --git a/lapi.c b/lapi.c
index 00e95a1..0f0e31a 100644
--- a/lapi.c
+++ b/lapi.c
@@ -187,9 +187,26 @@
api_check(L, -(idx+1) <= (L->top - (func + 1)), "invalid new top");
diff = idx + 1; /* will "subtract" index (as it is negative) */
}
+#if defined(LUA_COMPAT_5_4_0)
if (diff < 0 && hastocloseCfunc(ci->nresults))
luaF_close(L, L->top + diff, CLOSEKTOP);
- L->top += diff; /* correct top only after closing any upvalue */
+#endif
+ L->top += diff;
+ api_check(L, L->openupval == NULL || uplevel(L->openupval) < L->top,
+ "cannot pop an unclosed slot");
+ lua_unlock(L);
+}
+
+
+LUA_API void lua_closeslot (lua_State *L, int idx) {
+ StkId level;
+ lua_lock(L);
+ level = index2stack(L, idx);
+ api_check(L, hastocloseCfunc(L->ci->nresults) && L->openupval != NULL &&
+ uplevel(L->openupval) == level,
+ "no variable to close at given level");
+ luaF_close(L, level, CLOSEKTOP);
+ setnilvalue(s2v(level));
lua_unlock(L);
}
diff --git a/lauxlib.c b/lauxlib.c
index 074ff08..e8fc486 100644
--- a/lauxlib.c
+++ b/lauxlib.c
@@ -545,10 +545,8 @@
if (buffonstack(B)) /* buffer already has a box? */
newbuff = (char *)resizebox(L, boxidx, newsize); /* resize it */
else { /* no box yet */
- lua_pushnil(L); /* reserve slot for final result */
newbox(L); /* create a new box */
- /* move box (and slot) to its intended position */
- lua_rotate(L, boxidx - 1, 2);
+ lua_insert(L, boxidx); /* move box to its intended position */
lua_toclose(L, boxidx);
newbuff = (char *)resizebox(L, boxidx, newsize);
memcpy(newbuff, B->b, B->n * sizeof(char)); /* copy original content */
@@ -585,8 +583,8 @@
lua_State *L = B->L;
lua_pushlstring(L, B->b, B->n);
if (buffonstack(B)) {
- lua_copy(L, -1, -3); /* move string to reserved slot */
- lua_pop(L, 2); /* pop string and box (closing the box) */
+ lua_closeslot(L, -2); /* close the box */
+ lua_remove(L, -2); /* remove box from the stack */
}
}
diff --git a/ltests.c b/ltests.c
index 6920dd6..9c13338 100644
--- a/ltests.c
+++ b/ltests.c
@@ -1766,6 +1766,9 @@
else if EQ("toclose") {
lua_toclose(L1, getnum);
}
+ else if EQ("closeslot") {
+ lua_closeslot(L1, getnum);
+ }
else luaL_error(L, "unknown instruction %s", buff);
}
return 0;
diff --git a/lua.h b/lua.h
index c9d64d7..aec70da 100644
--- a/lua.h
+++ b/lua.h
@@ -347,7 +347,8 @@
LUA_API lua_Alloc (lua_getallocf) (lua_State *L, void **ud);
LUA_API void (lua_setallocf) (lua_State *L, lua_Alloc f, void *ud);
-LUA_API void (lua_toclose) (lua_State *L, int idx);
+LUA_API void (lua_toclose) (lua_State *L, int idx);
+LUA_API void (lua_closeslot) (lua_State *L, int idx);
/*
diff --git a/manual/manual.of b/manual/manual.of
index c538525..09297a6 100644
--- a/manual/manual.of
+++ b/manual/manual.of
@@ -3095,6 +3095,18 @@
}
+@APIEntry{void lua_closeslot (lua_State *L, int index);|
+@apii{0,0,e}
+
+Close the to-be-closed slot at the given index and set its value to @nil.
+The index must be the last index previously marked to be closed
+@see{lua_toclose} that is still active (that is, not closed yet).
+
+(Exceptionally, this function was introduced in release 5.4.3.
+It is not present in previous 5.4 releases.)
+
+}
+
@APIEntry{int lua_compare (lua_State *L, int index1, int index2, int op);|
@apii{0,0,e}
@@ -3747,9 +3759,7 @@
@apii{n,0,e}
Pops @id{n} elements from the stack.
-
-This function can run arbitrary code when removing an index
-marked as to-be-closed from the stack.
+It is implemented as a macro over @Lid{lua_settop}.
}
@@ -4240,8 +4250,12 @@
then the new elements are filled with @nil.
If @id{index} @N{is 0}, then all stack elements are removed.
-This function can run arbitrary code when removing an index
-marked as to-be-closed from the stack.
+For compatibility reasons,
+this function may close slots marked as to-be-closed @see{lua_toclose},
+and therefore it can run arbitrary code.
+You should not rely on this behavior:
+Instead, always close to-be-closed slots explicitly,
+with @Lid{lua_closeslot}, before removing them from the stack.
}
@@ -4337,10 +4351,9 @@
Here, in the context of a C function,
to go out of scope means that the running function returns to Lua,
there is an error,
-or the index is removed from the stack through
-@Lid{lua_settop} or @Lid{lua_pop}.
-An index marked as to-be-closed should not be removed from the stack
-by any other function in the API except @Lid{lua_settop} or @Lid{lua_pop}.
+or there is a call to @Lid{lua_closeslot}.
+An index marked as to-be-closed should neither be removed from the stack
+nor modified before a corresponding call to @Lid{lua_closeslot}.
This function should not be called for an index
that is equal to or below an active to-be-closed index.
@@ -4353,7 +4366,7 @@
by the time the @idx{__close} metamethod runs,
the @N{C stack} was already unwound,
so that any automatic @N{C variable} declared in the calling function
-will be out of scope.
+(e.g., a buffer) will be out of scope.
}
diff --git a/testes/api.lua b/testes/api.lua
index 9555148..fb7e708 100644
--- a/testes/api.lua
+++ b/testes/api.lua
@@ -507,10 +507,12 @@
end
if not _soft then
+ collectgarbage("stop") -- avoid __gc with full stack
checkerrnopro("pushnum 3; call 0 0", "attempt to call")
print"testing stack overflow in unprotected thread"
function f () f() end
checkerrnopro("getglobal 'f'; call 0 0;", "stack overflow")
+ collectgarbage("restart")
end
print"+"
@@ -1125,26 +1127,29 @@
assert(#openresource == n)
end
- -- closing resources with 'settop'
+ -- closing resources with 'closeslot'
+ _ENV.xxx = true
local a = T.testC([[
- pushvalue 2
- call 0 1 # create resource
+ pushvalue 2 # stack: S, NR, CH
+ call 0 1 # create resource; stack: S, NR, CH, R
toclose -1 # mark it to be closed
- pushvalue 2
- call 0 1 # create another resource
+ pushvalue 2 # stack: S, NR, CH, R, NR
+ call 0 1 # create another resource; stack: S, NR, CH, R, R
toclose -1 # mark it to be closed
- pushvalue 3
+ pushvalue 3 # stack: S, NR, CH, R, R, CH
pushint 2 # there should be two open resources
- call 1 0
- pop 1 # pop second resource from the stack
- pushvalue 3
+ call 1 0 # stack: S, NR, CH, R, R
+ closeslot -1 # close second resource
+ pushvalue 3 # stack: S, NR, CH, R, R, CH
pushint 1 # there should be one open resource
- call 1 0
- pop 1 # pop second resource from the stack
+ call 1 0 # stack: S, NR, CH, R, R
+ closeslot 4
+ setglobal "xxx" # previous op. erased the slot
+ pop 1 # pop other resource from the stack
pushint *
return 1 # return stack size
]], newresource, check)
- assert(a == 3) -- no extra items left in the stack
+ assert(a == 3 and _ENV.xxx == nil) -- no extra items left in the stack
-- non-closable value
local a, b = pcall(T.makeCfunc[[
