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>

5 files changed, 81 insertions, 49 deletions

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;