From: Jakub Jelinek <jakub@redhat.com>
To: Nathan Sidwell <nathan@acm.org>, Jason Merrill <jason@redhat.com>
Cc: gcc-patches@gcc.gnu.org
Subject: [PATCH] c++: Fix ICE on g++.dg/modules/adl-3_c.C [PR107379]
Date: Thu, 27 Oct 2022 10:17:09 +0200 [thread overview]
Message-ID: <Y1o+hfO6L6AGXcE4@tucnak> (raw)
Hi!
As mentioned in the PR, apparently my r13-2887 P1467R9 changes
regressed these tests on powerpc64le-linux with IEEE quad by default.
I believe my changes just uncovered a latent bug.
The problem is that push_namespace calls find_namespace_slot,
which does:
tree *slot = DECL_NAMESPACE_BINDINGS (ns)
->find_slot_with_hash (name, name ? IDENTIFIER_HASH_VALUE (name) : 0,
create_p ? INSERT : NO_INSERT);
In the <identifier_node 0x7fffe9f55ac0 details> ns case, slot is non-NULL
above with a binding_vector in it.
Then pushdecl is called and this does:
slot = find_namespace_slot (ns, name, ns == current_namespace);
where ns == current_namespace (ns is :: and name is details) is true.
So this again calls
tree *slot = DECL_NAMESPACE_BINDINGS (ns)
->find_slot_with_hash (name, name ? IDENTIFIER_HASH_VALUE (name) : 0,
create_p ? INSERT : NO_INSERT);
but this time with create_p and so INSERT.
At this point we reach
if (insert == INSERT && m_size * 3 <= m_n_elements * 4)
expand ();
and when we are unlucky and the occupancy of the hash table just reached 3/4,
expand () is called and the hash table is reallocated. But when that happens,
it means the slot pointer in the pushdecl caller (push_namespace) points to
freed memory and so any accesses to it in make_namespace_finish will be UB.
The following patch fixes it by calling find_namespace_slot again even if it
was non-NULL, just doesn't assert it is *slot == ns in that case (because
it often is not).
Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
2022-10-27 Jakub Jelinek <jakub@redhat.com>
PR c++/107379
* name-lookup.cc (push_namespace): Call find_namespace_slot again
after pushdecl as the hash table might be expanded during pushdecl.
--- gcc/cp/name-lookup.cc.jj 2022-10-12 17:51:00.912944731 +0200
+++ gcc/cp/name-lookup.cc 2022-10-26 12:06:38.177590655 +0200
@@ -8596,6 +8596,13 @@ push_namespace (tree name, bool make_inl
/* This should find the slot created by pushdecl. */
gcc_checking_assert (slot && *slot == ns);
}
+ else
+ {
+ /* pushdecl could have expanded the hash table, so
+ slot might be invalid. */
+ slot = find_namespace_slot (current_namespace, name);
+ gcc_checking_assert (slot);
+ }
make_namespace_finish (ns, slot);
/* Add the anon using-directive here, we don't do it in
Jakub
next reply other threads:[~2022-10-27 8:17 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-10-27 8:17 Jakub Jelinek [this message]
2022-10-27 10:21 ` Nathan Sidwell
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=Y1o+hfO6L6AGXcE4@tucnak \
--to=jakub@redhat.com \
--cc=gcc-patches@gcc.gnu.org \
--cc=jason@redhat.com \
--cc=nathan@acm.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).