reftable: signal overflow

reflog entries have unbounded size. In theory, each log ('g') block in reftable
can have an arbitrary size, so the format allows for arbitrarily sized reflog
messages. However, in the implementation, we are not scaling the log blocks up
with the message, and writing a large message fails.

This triggers a failure for reftable in t7006-pager.sh.

Until this is fixed more structurally, report an error from within the reftable
library for easier debugging.

Signed-off-by: Han-Wen Nienhuys <hanwen@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 35 insertions, 0 deletions

diff --git a/reftable/readwrite_test.c b/reftable/readwrite_test.c
index 5f6bcc2f77..70c7aedba2 100644
--- a/reftable/readwrite_test.c
+++ b/reftable/readwrite_test.c
@@ -155,6 +155,40 @@ static void test_log_buffer_size(void)
 	strbuf_release(&buf);
 }
 
+static void test_log_overflow(void)
+{
+	struct strbuf buf = STRBUF_INIT;
+	char msg[256] = { 0 };
+	struct reftable_write_options opts = {
+		.block_size = ARRAY_SIZE(msg),
+	};
+	int err;
+	struct reftable_log_record
+		log = { .refname = "refs/heads/master",
+			.update_index = 0xa,
+			.value_type = REFTABLE_LOG_UPDATE,
+			.value = { .update = {
+					   .name = "Han-Wen Nienhuys",
+					   .email = "hanwen@google.com",
+					   .tz_offset = 100,
+					   .time = 0x5e430672,
+					   .message = msg,
+				   } } };
+	struct reftable_writer *w =
+		reftable_new_writer(&strbuf_add_void, &buf, &opts);
+
+	uint8_t hash1[GIT_SHA1_RAWSZ]  = {1}, hash2[GIT_SHA1_RAWSZ] = { 2 };
+
+	memset(msg, 'x', sizeof(msg) - 1);
+	log.value.update.old_hash = hash1;
+	log.value.update.new_hash = hash2;
+	reftable_writer_set_limits(w, update_index, update_index);
+	err = reftable_writer_add_log(w, &log);
+	EXPECT(err == REFTABLE_ENTRY_TOO_BIG_ERROR);
+	reftable_writer_free(w);
+	strbuf_release(&buf);
+}
+
 static void test_log_write_read(void)
 {
 	int N = 2;
@@ -648,5 +682,6 @@ int readwrite_test_main(int argc, const char *argv[])
 	RUN_TEST(test_table_refs_for_no_index);
 	RUN_TEST(test_table_refs_for_obj_index);
 	RUN_TEST(test_write_empty_table);
+	RUN_TEST(test_log_overflow);
 	return 0;
 }