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To-be-closed variables must be closed on initialization

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When initializing a to-be-closed variable, check whether it has a
'__close' metamethod (or is a false value) and raise an error if
if it hasn't. This produces more accurate error messages. (The
check before closing still need to be done: in the C API, the value
is not constant; and the object may lose its '__close' metamethod
during the block.)
This commit is contained in:
Roberto Ierusalimschy
2019-07-31 10:43:51 -03:00
parent 35b4efc270
commit f645d31573
6 changed files with 70 additions and 41 deletions
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19
manual/manual.of
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@@ -1534,15 +1534,17 @@ or exiting by an error.
Here, to @emph{close} a value means
to call its @idx{__close} metamethod.
If the value is @nil, it is ignored;
otherwise,
if it does not have a @idx{__close} metamethod,
an error is raised.
When calling the metamethod,
the value itself is passed as the first argument
and the error object (if any) is passed as a second argument;
and the error object that caused the exit (if any)
is passed as a second argument;
if there was no error, the second argument is @nil.
The value assigned to a to-be-closed variable
must have a @idx{__close} metamethod
or be a false value.
(@nil and @false are ignored as to-be-closed values.)
If several to-be-closed variables go out of scope at the same event,
they are closed in the reverse order that they were declared.
@@ -2917,8 +2919,9 @@ it is left unchanged.
@APIEntry{void lua_close (lua_State *L);|
@apii{0,0,-}
Destroys all objects in the given Lua state
(calling the corresponding garbage-collection metamethods, if any)
Close all active to-be-closed variables in the main thread,
release all objects in the given Lua state
(calling the corresponding garbage-collection metamethods, if any),
and frees all dynamic memory used by this state.
On several platforms, you may not need to call this function,
@@ -4186,7 +4189,7 @@ 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}.
This function should not be called for an index
that is equal to or below an already marked to-be-closed index.
that is equal to or below an active to-be-closed index.
This function can raise an out-of-memory error.
In that case, the value in the given index is immediately closed,