mirror of https://github.com/lua/lua
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.
This commit is contained in:
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ce101dcaf7
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cc1692515e
19
lapi.c
19
lapi.c
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@ -187,9 +187,26 @@ LUA_API void lua_settop (lua_State *L, int idx) {
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api_check(L, -(idx+1) <= (L->top - (func + 1)), "invalid new top");
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diff = idx + 1; /* will "subtract" index (as it is negative) */
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}
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#if defined(LUA_COMPAT_5_4_0)
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if (diff < 0 && hastocloseCfunc(ci->nresults))
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luaF_close(L, L->top + diff, CLOSEKTOP);
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L->top += diff; /* correct top only after closing any upvalue */
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#endif
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L->top += diff;
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api_check(L, L->openupval == NULL || uplevel(L->openupval) < L->top,
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"cannot pop an unclosed slot");
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lua_unlock(L);
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}
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LUA_API void lua_closeslot (lua_State *L, int idx) {
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StkId level;
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lua_lock(L);
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level = index2stack(L, idx);
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api_check(L, hastocloseCfunc(L->ci->nresults) && L->openupval != NULL &&
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uplevel(L->openupval) == level,
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"no variable to close at given level");
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luaF_close(L, level, CLOSEKTOP);
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setnilvalue(s2v(level));
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lua_unlock(L);
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}
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@ -545,10 +545,8 @@ static char *prepbuffsize (luaL_Buffer *B, size_t sz, int boxidx) {
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if (buffonstack(B)) /* buffer already has a box? */
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newbuff = (char *)resizebox(L, boxidx, newsize); /* resize it */
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else { /* no box yet */
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lua_pushnil(L); /* reserve slot for final result */
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newbox(L); /* create a new box */
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/* move box (and slot) to its intended position */
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lua_rotate(L, boxidx - 1, 2);
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lua_insert(L, boxidx); /* move box to its intended position */
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lua_toclose(L, boxidx);
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newbuff = (char *)resizebox(L, boxidx, newsize);
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memcpy(newbuff, B->b, B->n * sizeof(char)); /* copy original content */
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@ -585,8 +583,8 @@ LUALIB_API void luaL_pushresult (luaL_Buffer *B) {
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lua_State *L = B->L;
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lua_pushlstring(L, B->b, B->n);
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if (buffonstack(B)) {
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lua_copy(L, -1, -3); /* move string to reserved slot */
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lua_pop(L, 2); /* pop string and box (closing the box) */
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lua_closeslot(L, -2); /* close the box */
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lua_remove(L, -2); /* remove box from the stack */
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}
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}
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3
ltests.c
3
ltests.c
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@ -1766,6 +1766,9 @@ static struct X { int x; } x;
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else if EQ("toclose") {
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lua_toclose(L1, getnum);
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}
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else if EQ("closeslot") {
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lua_closeslot(L1, getnum);
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}
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else luaL_error(L, "unknown instruction %s", buff);
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}
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return 0;
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3
lua.h
3
lua.h
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@ -347,7 +347,8 @@ LUA_API size_t (lua_stringtonumber) (lua_State *L, const char *s);
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LUA_API lua_Alloc (lua_getallocf) (lua_State *L, void **ud);
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LUA_API void (lua_setallocf) (lua_State *L, lua_Alloc f, void *ud);
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LUA_API void (lua_toclose) (lua_State *L, int idx);
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LUA_API void (lua_toclose) (lua_State *L, int idx);
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LUA_API void (lua_closeslot) (lua_State *L, int idx);
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/*
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@ -3095,6 +3095,18 @@ will probably need to close states as soon as they are not needed.
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}
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@APIEntry{void lua_closeslot (lua_State *L, int index);|
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@apii{0,0,e}
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Close the to-be-closed slot at the given index and set its value to @nil.
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The index must be the last index previously marked to be closed
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@see{lua_toclose} that is still active (that is, not closed yet).
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(Exceptionally, this function was introduced in release 5.4.3.
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It is not present in previous 5.4 releases.)
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}
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@APIEntry{int lua_compare (lua_State *L, int index1, int index2, int op);|
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@apii{0,0,e}
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@ -3747,9 +3759,7 @@ except that it allows the called function to yield @see{continuations}.
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@apii{n,0,e}
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Pops @id{n} elements from the stack.
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This function can run arbitrary code when removing an index
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marked as to-be-closed from the stack.
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It is implemented as a macro over @Lid{lua_settop}.
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}
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@ -4240,8 +4250,12 @@ If the new top is greater than the old one,
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then the new elements are filled with @nil.
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If @id{index} @N{is 0}, then all stack elements are removed.
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This function can run arbitrary code when removing an index
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marked as to-be-closed from the stack.
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For compatibility reasons,
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this function may close slots marked as to-be-closed @see{lua_toclose},
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and therefore it can run arbitrary code.
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You should not rely on this behavior:
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Instead, always close to-be-closed slots explicitly,
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with @Lid{lua_closeslot}, before removing them from the stack.
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}
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@ -4337,10 +4351,9 @@ when it goes out of scope.
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Here, in the context of a C function,
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to go out of scope means that the running function returns to Lua,
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there is an error,
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or the index is removed from the stack through
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@Lid{lua_settop} or @Lid{lua_pop}.
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An index marked as to-be-closed should not be removed from the stack
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by any other function in the API except @Lid{lua_settop} or @Lid{lua_pop}.
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or there is a call to @Lid{lua_closeslot}.
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An index marked as to-be-closed should neither be removed from the stack
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nor modified before a corresponding call to @Lid{lua_closeslot}.
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This function should not be called for an index
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that is equal to or below an active to-be-closed index.
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@ -4353,7 +4366,7 @@ Note that, both in case of errors and of a regular return,
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by the time the @idx{__close} metamethod runs,
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the @N{C stack} was already unwound,
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so that any automatic @N{C variable} declared in the calling function
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will be out of scope.
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(e.g., a buffer) will be out of scope.
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}
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@ -507,10 +507,12 @@ function checkerrnopro (code, msg)
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end
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if not _soft then
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collectgarbage("stop") -- avoid __gc with full stack
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checkerrnopro("pushnum 3; call 0 0", "attempt to call")
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print"testing stack overflow in unprotected thread"
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function f () f() end
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checkerrnopro("getglobal 'f'; call 0 0;", "stack overflow")
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collectgarbage("restart")
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end
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print"+"
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@ -1125,26 +1127,29 @@ do
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assert(#openresource == n)
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end
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-- closing resources with 'settop'
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-- closing resources with 'closeslot'
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_ENV.xxx = true
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local a = T.testC([[
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pushvalue 2
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call 0 1 # create resource
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pushvalue 2 # stack: S, NR, CH
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call 0 1 # create resource; stack: S, NR, CH, R
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toclose -1 # mark it to be closed
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pushvalue 2
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call 0 1 # create another resource
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pushvalue 2 # stack: S, NR, CH, R, NR
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call 0 1 # create another resource; stack: S, NR, CH, R, R
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toclose -1 # mark it to be closed
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pushvalue 3
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pushvalue 3 # stack: S, NR, CH, R, R, CH
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pushint 2 # there should be two open resources
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call 1 0
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pop 1 # pop second resource from the stack
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pushvalue 3
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call 1 0 # stack: S, NR, CH, R, R
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closeslot -1 # close second resource
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pushvalue 3 # stack: S, NR, CH, R, R, CH
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pushint 1 # there should be one open resource
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call 1 0
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pop 1 # pop second resource from the stack
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call 1 0 # stack: S, NR, CH, R, R
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closeslot 4
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setglobal "xxx" # previous op. erased the slot
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pop 1 # pop other resource from the stack
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pushint *
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return 1 # return stack size
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]], newresource, check)
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assert(a == 3) -- no extra items left in the stack
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assert(a == 3 and _ENV.xxx == nil) -- no extra items left in the stack
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-- non-closable value
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local a, b = pcall(T.makeCfunc[[
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