reftable/merged: handle allocation failures in `merged_table_init_iter()`

Handle allocation failures in `merged_table_init_iter()`. While at it,
merge `merged_iter_init()` into the function. It only has a single
caller and merging them makes it easier to handle allocation failures
consistently.

This change also requires us to adapt `reftable_stack_init_*_iterator()`
to bubble up the new error codes of `merged_table_iter_init()`. Adapt
callsites accordingly.

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

9 files changed, 131 insertions, 64 deletions

diff --git a/refs/reftable-backend.c b/refs/reftable-backend.c
index 3e63833ce4..9c2c695b13 100644
--- a/refs/reftable-backend.c
+++ b/refs/reftable-backend.c
@@ -1307,7 +1307,9 @@ static int write_transaction_table(struct reftable_writer *writer, void *cb_data
 			struct reftable_log_record log = {0};
 			struct reftable_iterator it = {0};
 
-			reftable_stack_init_log_iterator(arg->stack, &it);
+			ret = reftable_stack_init_log_iterator(arg->stack, &it);
+			if (ret < 0)
+				goto done;
 
 			/*
 			 * When deleting refs we also delete all reflog entries
@@ -1677,7 +1679,10 @@ static int write_copy_table(struct reftable_writer *writer, void *cb_data)
 	 * copy over all log entries from the old reflog. Last but not least,
 	 * when renaming we also have to delete all the old reflog entries.
 	 */
-	reftable_stack_init_log_iterator(arg->stack, &it);
+	ret = reftable_stack_init_log_iterator(arg->stack, &it);
+	if (ret < 0)
+		goto done;
+
 	ret = reftable_iterator_seek_log(&it, arg->oldname);
 	if (ret < 0)
 		goto done;
@@ -1898,7 +1903,10 @@ static struct reftable_reflog_iterator *reflog_iterator_for_stack(struct reftabl
 	if (ret < 0)
 		goto done;
 
-	reftable_stack_init_log_iterator(stack, &iter->iter);
+	ret = reftable_stack_init_log_iterator(stack, &iter->iter);
+	if (ret < 0)
+		goto done;
+
 	ret = reftable_iterator_seek_log(&iter->iter, "");
 	if (ret < 0)
 		goto done;
@@ -1965,7 +1973,10 @@ static int reftable_be_for_each_reflog_ent_reverse(struct ref_store *ref_store,
 	if (refs->err < 0)
 		return refs->err;
 
-	reftable_stack_init_log_iterator(stack, &it);
+	ret = reftable_stack_init_log_iterator(stack, &it);
+	if (ret < 0)
+		goto done;
+
 	ret = reftable_iterator_seek_log(&it, refname);
 	while (!ret) {
 		ret = reftable_iterator_next_log(&it, &log);
@@ -1981,6 +1992,7 @@ static int reftable_be_for_each_reflog_ent_reverse(struct ref_store *ref_store,
 			break;
 	}
 
+done:
 	reftable_log_record_release(&log);
 	reftable_iterator_destroy(&it);
 	return ret;
@@ -2002,7 +2014,10 @@ static int reftable_be_for_each_reflog_ent(struct ref_store *ref_store,
 	if (refs->err < 0)
 		return refs->err;
 
-	reftable_stack_init_log_iterator(stack, &it);
+	ret = reftable_stack_init_log_iterator(stack, &it);
+	if (ret < 0)
+		goto done;
+
 	ret = reftable_iterator_seek_log(&it, refname);
 	while (!ret) {
 		struct reftable_log_record log = {0};
@@ -2052,7 +2067,10 @@ static int reftable_be_reflog_exists(struct ref_store *ref_store,
 	if (ret < 0)
 		goto done;
 
-	reftable_stack_init_log_iterator(stack, &it);
+	ret = reftable_stack_init_log_iterator(stack, &it);
+	if (ret < 0)
+		goto done;
+
 	ret = reftable_iterator_seek_log(&it, refname);
 	if (ret < 0)
 		goto done;
@@ -2158,7 +2176,9 @@ static int write_reflog_delete_table(struct reftable_writer *writer, void *cb_da
 
 	reftable_writer_set_limits(writer, ts, ts);
 
-	reftable_stack_init_log_iterator(arg->stack, &it);
+	ret = reftable_stack_init_log_iterator(arg->stack, &it);
+	if (ret < 0)
+		goto out;
 
 	/*
 	 * In order to delete a table we need to delete all reflog entries one
@@ -2182,6 +2202,7 @@ static int write_reflog_delete_table(struct reftable_writer *writer, void *cb_da
 		ret = reftable_writer_add_log(writer, &tombstone);
 	}
 
+out:
 	reftable_log_record_release(&log);
 	reftable_iterator_destroy(&it);
 	return ret;
@@ -2320,7 +2341,9 @@ static int reftable_be_reflog_expire(struct ref_store *ref_store,
 	if (ret < 0)
 		goto done;
 
-	reftable_stack_init_log_iterator(stack, &it);
+	ret = reftable_stack_init_log_iterator(stack, &it);
+	if (ret < 0)
+		goto done;
 
 	ret = reftable_iterator_seek_log(&it, refname);
 	if (ret < 0)
diff --git a/reftable/merged.c b/reftable/merged.c
index 128a810c55..de4f81abaf 100644
--- a/reftable/merged.c
+++ b/reftable/merged.c
@@ -30,22 +30,6 @@ struct merged_iter {
 	ssize_t advance_index;
 };
 
-static void merged_iter_init(struct merged_iter *mi,
-			     struct reftable_merged_table *mt,
-			     uint8_t typ)
-{
-	memset(mi, 0, sizeof(*mi));
-	mi->advance_index = -1;
-	mi->suppress_deletions = mt->suppress_deletions;
-
-	REFTABLE_CALLOC_ARRAY(mi->subiters, mt->readers_len);
-	for (size_t i = 0; i < mt->readers_len; i++) {
-		reftable_record_init(&mi->subiters[i].rec, typ);
-		reader_init_iter(mt->readers[i], &mi->subiters[i].iter, typ);
-	}
-	mi->subiters_len = mt->readers_len;
-}
-
 static void merged_iter_close(void *p)
 {
 	struct merged_iter *mi = p;
@@ -244,25 +228,61 @@ reftable_merged_table_min_update_index(struct reftable_merged_table *mt)
 	return mt->min;
 }
 
-void merged_table_init_iter(struct reftable_merged_table *mt,
-			    struct reftable_iterator *it,
-			    uint8_t typ)
+int merged_table_init_iter(struct reftable_merged_table *mt,
+			   struct reftable_iterator *it,
+			   uint8_t typ)
 {
-	struct merged_iter *mi = reftable_malloc(sizeof(*mi));
-	merged_iter_init(mi, mt, typ);
+	struct merged_subiter *subiters;
+	struct merged_iter *mi = NULL;
+	int ret;
+
+	REFTABLE_CALLOC_ARRAY(subiters, mt->readers_len);
+	if (!subiters) {
+		ret = REFTABLE_OUT_OF_MEMORY_ERROR;
+		goto out;
+	}
+
+	for (size_t i = 0; i < mt->readers_len; i++) {
+		reftable_record_init(&subiters[i].rec, typ);
+		reader_init_iter(mt->readers[i], &subiters[i].iter, typ);
+	}
+
+	REFTABLE_CALLOC_ARRAY(mi, 1);
+	if (!mi) {
+		ret = REFTABLE_OUT_OF_MEMORY_ERROR;
+		goto out;
+	}
+	mi->advance_index = -1;
+	mi->suppress_deletions = mt->suppress_deletions;
+	mi->subiters = subiters;
+	mi->subiters_len = mt->readers_len;
+
 	iterator_from_merged_iter(it, mi);
+	ret = 0;
+
+out:
+	if (ret < 0) {
+		for (size_t i = 0; subiters && i < mt->readers_len; i++) {
+			reftable_iterator_destroy(&subiters[i].iter);
+			reftable_record_release(&subiters[i].rec);
+		}
+		reftable_free(subiters);
+		reftable_free(mi);
+	}
+
+	return ret;
 }
 
-void reftable_merged_table_init_ref_iterator(struct reftable_merged_table *mt,
-					     struct reftable_iterator *it)
+int reftable_merged_table_init_ref_iterator(struct reftable_merged_table *mt,
+					    struct reftable_iterator *it)
 {
-	merged_table_init_iter(mt, it, BLOCK_TYPE_REF);
+	return merged_table_init_iter(mt, it, BLOCK_TYPE_REF);
 }
 
-void reftable_merged_table_init_log_iterator(struct reftable_merged_table *mt,
-					     struct reftable_iterator *it)
+int reftable_merged_table_init_log_iterator(struct reftable_merged_table *mt,
+					    struct reftable_iterator *it)
 {
-	merged_table_init_iter(mt, it, BLOCK_TYPE_LOG);
+	return merged_table_init_iter(mt, it, BLOCK_TYPE_LOG);
 }
 
 uint32_t reftable_merged_table_hash_id(struct reftable_merged_table *mt)
diff --git a/reftable/merged.h b/reftable/merged.h
index de5fd33f01..89bd0c4b35 100644
--- a/reftable/merged.h
+++ b/reftable/merged.h
@@ -26,8 +26,8 @@ struct reftable_merged_table {
 
 struct reftable_iterator;
 
-void merged_table_init_iter(struct reftable_merged_table *mt,
-			    struct reftable_iterator *it,
-			    uint8_t typ);
+int merged_table_init_iter(struct reftable_merged_table *mt,
+			   struct reftable_iterator *it,
+			   uint8_t typ);
 
 #endif
diff --git a/reftable/reftable-merged.h b/reftable/reftable-merged.h
index 16d19f8df2..a970d5dd89 100644
--- a/reftable/reftable-merged.h
+++ b/reftable/reftable-merged.h
@@ -37,12 +37,12 @@ int reftable_merged_table_new(struct reftable_merged_table **dest,
 			      uint32_t hash_id);
 
 /* Initialize a merged table iterator for reading refs. */
-void reftable_merged_table_init_ref_iterator(struct reftable_merged_table *mt,
-					     struct reftable_iterator *it);
+int reftable_merged_table_init_ref_iterator(struct reftable_merged_table *mt,
+					    struct reftable_iterator *it);
 
 /* Initialize a merged table iterator for reading logs. */
-void reftable_merged_table_init_log_iterator(struct reftable_merged_table *mt,
-					     struct reftable_iterator *it);
+int reftable_merged_table_init_log_iterator(struct reftable_merged_table *mt,
+					    struct reftable_iterator *it);
 
 /* returns the max update_index covered by this merged table. */
 uint64_t
diff --git a/reftable/reftable-stack.h b/reftable/reftable-stack.h
index f4f8cabc7f..e958f911b4 100644
--- a/reftable/reftable-stack.h
+++ b/reftable/reftable-stack.h
@@ -73,16 +73,16 @@ struct reftable_iterator;
  * be used to iterate through refs. The iterator is valid until the next reload
  * or write.
  */
-void reftable_stack_init_ref_iterator(struct reftable_stack *st,
-				      struct reftable_iterator *it);
+int reftable_stack_init_ref_iterator(struct reftable_stack *st,
+				     struct reftable_iterator *it);
 
 /*
  * Initialize an iterator for the merged tables contained in the stack that can
  * be used to iterate through logs. The iterator is valid until the next reload
  * or write.
  */
-void reftable_stack_init_log_iterator(struct reftable_stack *st,
-				      struct reftable_iterator *it);
+int reftable_stack_init_log_iterator(struct reftable_stack *st,
+				     struct reftable_iterator *it);
 
 /* returns the merged_table for seeking. This table is valid until the
  * next write or reload, and should not be closed or deleted.
diff --git a/reftable/stack.c b/reftable/stack.c
index ea21ca6e5f..bb4d230918 100644
--- a/reftable/stack.c
+++ b/reftable/stack.c
@@ -136,18 +136,18 @@ int read_lines(const char *filename, char ***namesp)
 	return err;
 }
 
-void reftable_stack_init_ref_iterator(struct reftable_stack *st,
+int reftable_stack_init_ref_iterator(struct reftable_stack *st,
 				      struct reftable_iterator *it)
 {
-	merged_table_init_iter(reftable_stack_merged_table(st),
-			       it, BLOCK_TYPE_REF);
+	return merged_table_init_iter(reftable_stack_merged_table(st),
+				      it, BLOCK_TYPE_REF);
 }
 
-void reftable_stack_init_log_iterator(struct reftable_stack *st,
-				      struct reftable_iterator *it)
+int reftable_stack_init_log_iterator(struct reftable_stack *st,
+				     struct reftable_iterator *it)
 {
-	merged_table_init_iter(reftable_stack_merged_table(st),
-			       it, BLOCK_TYPE_LOG);
+	return merged_table_init_iter(reftable_stack_merged_table(st),
+				      it, BLOCK_TYPE_LOG);
 }
 
 struct reftable_merged_table *
@@ -952,7 +952,10 @@ static int stack_write_compact(struct reftable_stack *st,
 	if (err < 0)
 		goto done;
 
-	merged_table_init_iter(mt, &it, BLOCK_TYPE_REF);
+	err = merged_table_init_iter(mt, &it, BLOCK_TYPE_REF);
+	if (err < 0)
+		goto done;
+
 	err = reftable_iterator_seek_ref(&it, "");
 	if (err < 0)
 		goto done;
@@ -977,7 +980,10 @@ static int stack_write_compact(struct reftable_stack *st,
 	}
 	reftable_iterator_destroy(&it);
 
-	merged_table_init_iter(mt, &it, BLOCK_TYPE_LOG);
+	err = merged_table_init_iter(mt, &it, BLOCK_TYPE_LOG);
+	if (err < 0)
+		goto done;
+
 	err = reftable_iterator_seek_log(&it, "");
 	if (err < 0)
 		goto done;
@@ -1496,7 +1502,10 @@ int reftable_stack_read_ref(struct reftable_stack *st, const char *refname,
 	struct reftable_iterator it = { 0 };
 	int ret;
 
-	reftable_merged_table_init_ref_iterator(st->merged, &it);
+	ret = reftable_merged_table_init_ref_iterator(st->merged, &it);
+	if (ret)
+		goto out;
+
 	ret = reftable_iterator_seek_ref(&it, refname);
 	if (ret)
 		goto out;
@@ -1523,7 +1532,10 @@ int reftable_stack_read_log(struct reftable_stack *st, const char *refname,
 	struct reftable_iterator it = {0};
 	int err;
 
-	reftable_stack_init_log_iterator(st, &it);
+	err = reftable_stack_init_log_iterator(st, &it);
+	if (err)
+		goto done;
+
 	err = reftable_iterator_seek_log(&it, refname);
 	if (err)
 		goto done;
diff --git a/t/helper/test-reftable.c b/t/helper/test-reftable.c
index 29d4e9a755..5c8849d115 100644
--- a/t/helper/test-reftable.c
+++ b/t/helper/test-reftable.c
@@ -28,7 +28,10 @@ static int dump_table(struct reftable_merged_table *mt)
 	const struct git_hash_algo *algop;
 	int err;
 
-	reftable_merged_table_init_ref_iterator(mt, &it);
+	err = reftable_merged_table_init_ref_iterator(mt, &it);
+	if (err < 0)
+		return err;
+
 	err = reftable_iterator_seek_ref(&it, "");
 	if (err < 0)
 		return err;
@@ -63,7 +66,10 @@ static int dump_table(struct reftable_merged_table *mt)
 	reftable_iterator_destroy(&it);
 	reftable_ref_record_release(&ref);
 
-	reftable_merged_table_init_log_iterator(mt, &it);
+	err = reftable_merged_table_init_log_iterator(mt, &it);
+	if (err < 0)
+		return err;
+
 	err = reftable_iterator_seek_log(&it, "");
 	if (err < 0)
 		return err;
diff --git a/t/unit-tests/t-reftable-merged.c b/t/unit-tests/t-reftable-merged.c
index 19e54bdfb8..3d2848632d 100644
--- a/t/unit-tests/t-reftable-merged.c
+++ b/t/unit-tests/t-reftable-merged.c
@@ -82,7 +82,8 @@ static void t_merged_single_record(void)
 	struct reftable_iterator it = { 0 };
 	int err;
 
-	merged_table_init_iter(mt, &it, BLOCK_TYPE_REF);
+	err = merged_table_init_iter(mt, &it, BLOCK_TYPE_REF);
+	check(!err);
 	err = reftable_iterator_seek_ref(&it, "a");
 	check(!err);
 
@@ -161,7 +162,8 @@ static void t_merged_refs(void)
 	size_t cap = 0;
 	size_t i;
 
-	merged_table_init_iter(mt, &it, BLOCK_TYPE_REF);
+	err = merged_table_init_iter(mt, &it, BLOCK_TYPE_REF);
+	check(!err);
 	err = reftable_iterator_seek_ref(&it, "a");
 	check(!err);
 	check_int(reftable_merged_table_hash_id(mt), ==, GIT_SHA1_FORMAT_ID);
@@ -367,7 +369,8 @@ static void t_merged_logs(void)
 	size_t cap = 0;
 	size_t i;
 
-	merged_table_init_iter(mt, &it, BLOCK_TYPE_LOG);
+	err = merged_table_init_iter(mt, &it, BLOCK_TYPE_LOG);
+	check(!err);
 	err = reftable_iterator_seek_log(&it, "a");
 	check(!err);
 	check_int(reftable_merged_table_hash_id(mt), ==, GIT_SHA1_FORMAT_ID);
@@ -390,7 +393,8 @@ static void t_merged_logs(void)
 		check(reftable_log_record_equal(want[i], &out[i],
 						 GIT_SHA1_RAWSZ));
 
-	merged_table_init_iter(mt, &it, BLOCK_TYPE_LOG);
+	err = merged_table_init_iter(mt, &it, BLOCK_TYPE_LOG);
+	check(!err);
 	err = reftable_iterator_seek_log_at(&it, "a", 2);
 	check(!err);
 	reftable_log_record_release(&out[0]);
diff --git a/t/unit-tests/t-reftable-stack.c b/t/unit-tests/t-reftable-stack.c
index 65e513d5ec..6e41a4cf7e 100644
--- a/t/unit-tests/t-reftable-stack.c
+++ b/t/unit-tests/t-reftable-stack.c
@@ -599,7 +599,9 @@ static void t_reftable_stack_iterator(void)
 
 	reftable_iterator_destroy(&it);
 
-	reftable_stack_init_log_iterator(st, &it);
+	err = reftable_stack_init_log_iterator(st, &it);
+	check(!err);
+
 	reftable_iterator_seek_log(&it, logs[0].refname);
 	for (i = 0; ; i++) {
 		struct reftable_log_record log = { 0 };