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Finalizers must be callable

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Non-function __gc metamethods are not ignored; if present, the
metamethod will be called even if it is not a function.
This commit is contained in:
Roberto Ierusalimschy 2019-03-14 15:53:42 -03:00
parent b56d4e570a
commit 8fa4f1380b
2 changed files with 20 additions and 5 deletions
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2
lgc.c
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@ -832,7 +832,7 @@ static void GCTM (lua_State *L) {
lua_assert(!g->gcemergency);
setgcovalue(L, &v, udata2finalize(g));
tm = luaT_gettmbyobj(L, &v, TM_GC);
if (ttisfunction(tm)) { /* is the finalizer a function? */
if (!notm(tm)) { /* is there a finalizer? */
int status;
lu_byte oldah = L->allowhook;
int running = g->gcrunning;

23
manual/manual.of
View File

@ -689,10 +689,8 @@ After the collection,
Lua goes through that list.
For each object in the list,
it checks the object's @idx{__gc} metamethod:
If it is a function,
Lua calls it with the object as its single argument;
if the metamethod is not a function,
Lua simply ignores it.
If it is present,
Lua calls it with the object as its single argument.
At the end of each garbage-collection cycle,
the finalizers for objects are called in
@ -726,6 +724,9 @@ these marks have no effect.
Finalizers cannot yield.
Any error while running a finalizer generates a warning;
it is not propagated.
}
@sect3{weak-table| @title{Weak Tables}
@ -7279,6 +7280,11 @@ that is,
with maximum alignment of 1 (no alignment)
and native endianness.
Native endianness assumes that the whole system is
either big or little endian.
The packing functions will not emulate correctly the behavior
of mixed-endian formats.
Alignment works as follows:
For each option,
the format gets extra padding until the data starts
@ -7288,6 +7294,7 @@ this minimum must be a power of 2.
Options @St{c} and @St{z} are not aligned;
option @St{s} follows the alignment of its starting integer.
All padding is filled with zeros by @Lid{string.pack}
(and ignored by @Lid{string.unpack}).
@ -8720,6 +8727,14 @@ name is visible, even if this other label is declared in an enclosing
block.
}
@item{
When finalizing an object,
Lua does not ignore @idx{__gc} metamethods that are not functions.
Any value will be called, if present.
(Non-callable values will generate a warning,
like any other error when calling a finalizer.)
}
}
}