Re: Bug in Lua 5.4-work2's generational GC with LPEG
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- Subject: Re: Bug in Lua 5.4-work2's generational GC with LPEG
- From: Roberto Ierusalimschy <roberto@...>
- Date: 2018年9月11日 08:30:26 -0300
> Bruce> While working on a project, I encountered what I think is a bug
> Bruce> in Lua 5.4-work2's generational garbage collection as it
> Bruce> interacts with LPEG.
>
> A while back (July?) I posted an analysis of a bug in work2's
> generational GC that applied to all uses of the uservalue slots of
> userdata objects. I haven't checked that this is the same bug, but I'd
> bet that it is; the issue is easily triggered with the 're' module of
> LPEG.
>
> Roberto is aware of it, so I guess we can hope for it to be fixed in
> work3 or whatever the next release is.
I guess this fixes the bug (following Gierth's analysis):
In lgc.c:
static int traverseudata (global_State *g, Udata *u) {
int i;
markobjectN(g, u->metatable); /* mark its metatable */
for (i = 0; i < u->nuvalue; i++)
markvalue(g, &u->uv[i].uv);
+ if (g->gckind == KGC_GEN) {
+ linkgclist(u, g->grayagain); /* keep it in some gray list */
+ black2gray(u);
+ }
return 1 + u->nuvalue;
}
-- Roberto