From: Valentin Gatien-Baron <vgatien-baron@janestreet.com>
To: Andreas Schwab <schwab@linux-m68k.org>
Cc: 29066@debbugs.gnu.org, Mark Shinwell <mshinwell@janestreet.com>
Subject: bug#29066: 26.0.90; crash in gc involving buffer local symbols
Date: Tue, 31 Oct 2017 10:52:44 -0400 [thread overview]
Message-ID: <CAFd54qPr9H1U5Buf+mB0ytf53ewaa3MaAScdRYwYuG=AjzoT-Q@mail.gmail.com> (raw)
In-Reply-To: <87efpjzv2p.fsf@linux-m68k.org>
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On Tue, Oct 31, 2017 at 2:32 AM, Andreas Schwab <schwab@linux-m68k.org>
wrote:
> On Okt 31 2017, Eli Zaretskii <eliz@gnu.org> wrote:
>
> >> I also checked the following works, and seems better to me (stop having
> dangling pointers, instead of being
> >> careful with them):
> >>
> >> diff --git a/src/alloc.c b/src/alloc.c
> >> index da0c3ad4b3..44dfa95cf5 100644
> >> --- a/src/alloc.c
> >> +++ b/src/alloc.c
> >> @@ -7030,8 +7030,10 @@ sweep_symbols (void)
> >> {
> >> if (!sym->s.gcmarkbit)
> >> {
> >> - if (sym->s.redirect == SYMBOL_LOCALIZED)
> >> + if (sym->s.redirect == SYMBOL_LOCALIZED) {
> >> xfree (SYMBOL_BLV (&sym->s));
> >> + sym->s.val.blv = NULL;
> >> + }
> >
> > That was my first attempt, but various macros like SYMBOL_BLV and
> > SET_SYMBOL_BLV insist on val.blv being non-NULL.
>
> SET_SYMBOL_BLV doesn't. And calling SYMBOL_BLV with a freed symbol is a
> bug anyway.
>
SET_SYMBOL_BLV insists that the new value is not NULL, even if it asserts
nothing about the current value.
We do call SYMBOL_BLV after freeing, when we re-sweep the symbol, which is
fine because free does nothing when given NULL, but triggers the assertion.
I would do this, to avoid the assertion failure:
diff --git a/src/alloc.c b/src/alloc.c
index da0c3ad4b3..72550e812b 100644
--- a/src/alloc.c
+++ b/src/alloc.c
@@ -7030,8 +7030,10 @@ sweep_symbols (void)
{
if (!sym->s.gcmarkbit)
{
- if (sym->s.redirect == SYMBOL_LOCALIZED)
+ if (sym->s.redirect == SYMBOL_LOCALIZED && sym->s.val.blv) {
xfree (SYMBOL_BLV (&sym->s));
+ sym->s.val.blv = NULL;
+ }
sym->s.next = symbol_free_list;
symbol_free_list = &sym->s;
symbol_free_list->function = Vdead;
Or changing the redirect type:
diff --git a/src/alloc.c b/src/alloc.c
index da0c3ad4b3..6966d96c6d 100644
--- a/src/alloc.c
+++ b/src/alloc.c
@@ -7030,8 +7030,11 @@ sweep_symbols (void)
{
if (!sym->s.gcmarkbit)
{
- if (sym->s.redirect == SYMBOL_LOCALIZED)
+ if (sym->s.redirect == SYMBOL_LOCALIZED) {
xfree (SYMBOL_BLV (&sym->s));
+ sym->s.redirect = SYMBOL_PLAINVAL;
+ SET_SYMBOL_VAL (&sym->s, Qunbound);
+ }
sym->s.next = symbol_free_list;
symbol_free_list = &sym->s;
symbol_free_list->function = Vdead;
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next prev parent reply other threads:[~2017-10-31 14:52 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-10-30 14:36 bug#29066: 26.0.90; crash in gc involving buffer local symbols Valentin Gatien-Baron
2017-10-30 20:38 ` Eli Zaretskii
2017-10-30 22:04 ` Valentin Gatien-Baron
2017-10-31 3:39 ` Eli Zaretskii
2017-10-31 6:32 ` Andreas Schwab
2017-10-31 14:52 ` Valentin Gatien-Baron [this message]
2017-10-31 19:10 ` Eli Zaretskii
2017-10-31 19:58 ` Valentin Gatien-Baron
2017-10-31 20:09 ` Eli Zaretskii
2017-10-31 20:13 ` Valentin Gatien-Baron
2017-10-31 18:59 ` Eli Zaretskii
2017-10-31 20:23 ` Andreas Schwab
2017-10-31 20:34 ` Eli Zaretskii
2017-10-31 21:03 ` Andreas Schwab
2017-10-31 21:08 ` Eli Zaretskii
2017-10-31 22:00 ` Andreas Schwab
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