From: Patrick Steinhardt <ps@pks.im>
Date: Thu, 23 Oct 2025 07:16:12 +0000 (+0200)
Subject: refs: fully reset `struct ref_iterator::ref` on iteration
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=4cea0422879f6a64c0f7ad0ddac6d43897a53e94;p=thirdparty%2Fgit.git

refs: fully reset `struct ref_iterator::ref` on iteration

With the introduction of the `struct ref_iterator::ref` field it now is
a whole lot easier to introduce new fields that become accessible to the
caller without having to adapt every single callsite. But there's a
downside: when a new field is introduced we always have to adapt all
backends to set that field.

This isn't something we can avoid in the general case: when the new
field is expected to be populated by all backends we of course cannot
avoid doing so. But new fields may be entirely optional, in which case
we'd still have such churn. And furthermore, it is very easy right now
to leak state from a previous iteration into the next iteration.

Address this issue by ensuring that the reference backends all fully
reset the field on every single iteration. This ensures that no state
from previous iterations can leak into the next one. And it ensures that
any newly introduced fields will be zeroed out by default.

Note that we don't have to explicitly adapt the "files" backend, as it
uses the `cache_ref_iterator` internally. Furthermore, other "wrapping"
iterators like for example the `prefix_ref_iterator` copy around the
whole reference, so these don't need to be adapted either.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
---

diff --git a/refs/packed-backend.c b/refs/packed-backend.c
index 7987acdc96..711e07f832 100644
--- a/refs/packed-backend.c
+++ b/refs/packed-backend.c
@@ -882,6 +882,7 @@ static int next_record(struct packed_ref_iterator *iter)
 {
 	const char *p, *eol;
 
+	memset(&iter->base.ref, 0, sizeof(iter->base.ref));
 	strbuf_reset(&iter->refname_buf);
 
 	/*
@@ -916,6 +917,7 @@ static int next_record(struct packed_ref_iterator *iter)
 	    !isspace(*p++))
 		die_invalid_line(iter->snapshot->refs->path,
 				 iter->pos, iter->eof - iter->pos);
+	iter->base.ref.oid = &iter->oid;
 
 	eol = memchr(p, '\n', iter->eof - p);
 	if (!eol)
@@ -1194,7 +1196,6 @@ static struct ref_iterator *packed_ref_iterator_begin(
 	iter->snapshot = snapshot;
 	acquire_snapshot(snapshot);
 	strbuf_init(&iter->refname_buf, 0);
-	iter->base.ref.oid = &iter->oid;
 	iter->repo = ref_store->repo;
 	iter->flags = flags;
 
diff --git a/refs/ref-cache.c b/refs/ref-cache.c
index f1abc39624..e427848879 100644
--- a/refs/ref-cache.c
+++ b/refs/ref-cache.c
@@ -425,6 +425,7 @@ static int cache_ref_iterator_advance(struct ref_iterator *ref_iterator)
 			level->prefix_state = entry_prefix_state;
 			level->index = -1;
 		} else {
+			memset(&iter->base.ref, 0, sizeof(iter->base.ref));
 			iter->base.ref.name = entry->name;
 			iter->base.ref.target = entry->u.value.referent;
 			iter->base.ref.oid = &entry->u.value.oid;
diff --git a/refs/reftable-backend.c b/refs/reftable-backend.c
index 0e47986cb5..728886eafd 100644
--- a/refs/reftable-backend.c
+++ b/refs/reftable-backend.c
@@ -704,6 +704,7 @@ static int reftable_ref_iterator_advance(struct ref_iterator *ref_iterator)
 					    &iter->oid, flags))
 				continue;
 
+		memset(&iter->base.ref, 0, sizeof(iter->base.ref));
 		iter->base.ref.name = iter->ref.refname;
 		iter->base.ref.target = referent;
 		iter->base.ref.oid = &iter->oid;