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lua_settop/lua_pop closes to-be-closed variables

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The existence of 'lua_closeslot' is no reason for lua_pop not to close
to-be-closed variables too.  It is too error-prone for lua_pop not to
close tbc variables being popped from the stack.
This commit is contained in:
Roberto Ierusalimschy
2021-03-09 11:42:45 -03:00
parent f5df7f91f7
commit 511d53a826
3 changed files with 44 additions and 20 deletions
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23
manual/manual.of
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@@ -4253,12 +4253,8 @@ If the new top is greater than the old one,
then the new elements are filled with @nil.
If @id{index} @N{is 0}, then all stack elements are removed.
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.
This function can run arbitrary code when removing an index
marked as to-be-closed from the stack.
}
@@ -4347,19 +4343,22 @@ otherwise, returns @id{NULL}.
@apii{0,0,m}
Marks the given index in the stack as a
to-be-closed @Q{variable} @see{to-be-closed}.
to-be-closed slot @see{to-be-closed}.
Like a to-be-closed variable in Lua,
the value at that index in the stack will be closed
the value at that slot in the stack will be closed
when it goes out of scope.
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 there is an error,
or the slot is removed from the stack through
@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}.
A slot 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},
unless previously deactivated by @Lid{lua_closeslot}.
This function should not be called for an index
that is equal to or below an active to-be-closed index.
that is equal to or below an active to-be-closed slot.
Note that, both in case of errors and of a regular return,
by the time the @idx{__close} metamethod runs,