[PATCH] Fix maybe-uninitialized warnings found by gcc 9 -flto

[Stephan Beyer <s-beyer@gmx.net>]

Compiler heuristics for detection of potentially uninitialized variables
may change between compiler versions and enabling link-time optimization
may find new warnings.  Indeed, compiling with gcc 9.2.1 and enabled
link-time optimization feature resulted in a few hits that are fixed by
this patch in the most naïve way.  This allows to compile git using the
DEVELOPER=1 switch (which sets -Werror) and using the -flto flag.

Signed-off-by: Stephan Beyer <s-beyer@gmx.net>
---
 builtin/am.c               | 2 +-
 builtin/pack-objects.c     | 2 +-
 bulk-checkin.c             | 2 ++
 fast-import.c              | 3 ++-
 t/helper/test-read-cache.c | 2 +-
 5 files changed, 7 insertions(+), 4 deletions(-)

diff --git a/builtin/am.c b/builtin/am.c
index 1aea657a7f..ab914fd46e 100644
--- a/builtin/am.c
+++ b/builtin/am.c
@@ -1266,7 +1266,7 @@ static int get_mail_commit_oid(struct object_id *commit_id, const char *mail)
 static void get_commit_info(struct am_state *state, struct commit *commit)
 {
 	const char *buffer, *ident_line, *msg;
-	size_t ident_len;
+	size_t ident_len = 0;
 	struct ident_split id;

 	buffer = logmsg_reencode(commit, NULL, get_commit_output_encoding());
diff --git a/builtin/pack-objects.c b/builtin/pack-objects.c
index 76ce906946..d0c03b0e9b 100644
--- a/builtin/pack-objects.c
+++ b/builtin/pack-objects.c
@@ -1171,7 +1171,7 @@ static int add_object_entry(const struct object_id *oid, enum object_type type,
 {
 	struct packed_git *found_pack = NULL;
 	off_t found_offset = 0;
-	uint32_t index_pos;
+	uint32_t index_pos = 0;

 	display_progress(progress_state, ++nr_seen);

diff --git a/bulk-checkin.c b/bulk-checkin.c
index 39ee7d6107..87fa28c227 100644
--- a/bulk-checkin.c
+++ b/bulk-checkin.c
@@ -200,6 +200,8 @@ static int deflate_to_pack(struct bulk_checkin_state *state,
 	struct hashfile_checkpoint checkpoint;
 	struct pack_idx_entry *idx = NULL;

+	checkpoint.offset = 0;
+
 	seekback = lseek(fd, 0, SEEK_CUR);
 	if (seekback == (off_t) -1)
 		return error("cannot find the current offset");
diff --git a/fast-import.c b/fast-import.c
index b44d6a467e..58f73f9105 100644
--- a/fast-import.c
+++ b/fast-import.c
@@ -903,7 +903,8 @@ static int store_object(
 	struct object_entry *e;
 	unsigned char hdr[96];
 	struct object_id oid;
-	unsigned long hdrlen, deltalen;
+	unsigned long hdrlen;
+	unsigned long deltalen = 0;
 	git_hash_ctx c;
 	git_zstream s;

diff --git a/t/helper/test-read-cache.c b/t/helper/test-read-cache.c
index 7e79b555de..ef0963e2f4 100644
--- a/t/helper/test-read-cache.c
+++ b/t/helper/test-read-cache.c
@@ -4,7 +4,7 @@

 int cmd__read_cache(int argc, const char **argv)
 {
-	int i, cnt = 1, namelen;
+	int i, cnt = 1, namelen = 0;
 	const char *name = NULL;

 	if (argc > 1 && skip_prefix(argv[1], "--print-and-refresh=", &name)) {
--
2.23.0.38.g7ab3f3815a