[PATCH 6/8] compat/zlib: provide stubs for `deflateSetHeader()`

From: Patrick Steinhardt <ps@pks.im>
Date: Jan 10, 2025, 12:55 UTC
Message-ID: <20250110-b4-pks-compat-drop-uncompress2-v1-6-965d0022a74d@pks.im>
In-Reply-To: <20250110-b4-pks-compat-drop-uncompress2-v1-0-965d0022a74d@pks.im>

The function `deflateSetHeader()` has been introduce with zlib v1.2.2.1, so we don't use it when linking against an older version of it. Refactor the code to instead provide a central stub via "compat/zlib.h" so that we can adapt it based on whether or not we use zlib-ng in a subsequent commit.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
---
 archive-tar.c        |  4 ----
 compat/zlib-compat.h | 13 +++++++++++++
 2 files changed, 13 insertions(+), 4 deletions(-)

diff --git a/archive-tar.c b/archive-tar.c
index e7b3489e1e6c826d8128cddb0c5be04042a65cec..0edf13fba7568b3950978a05a2f50299bb9b2f18 100644
--- a/archive-tar.c
+++ b/archive-tar.c
@@ -473,9 +473,7 @@ static const char internal_gzip_command[] = "git archive gzip";
 static int write_tar_filter_archive(const struct archiver *ar,
 				    struct archiver_args *args)
 {
-#if ZLIB_VERNUM >= 0x1221
 	struct gz_header_s gzhead = { .os = 3 }; /* Unix, for reproducibility */
-#endif
 	struct strbuf cmd = STRBUF_INIT;
 	struct child_process filter = CHILD_PROCESS_INIT;
 	int r;
@@ -486,10 +484,8 @@ static int write_tar_filter_archive(const struct archiver *ar,
 	if (!strcmp(ar->filter_command, internal_gzip_command)) {
 		write_block = tgz_write_block;
 		git_deflate_init_gzip(&gzstream, args->compression_level);
-#if ZLIB_VERNUM >= 0x1221
 		if (deflateSetHeader(&gzstream.z, &gzhead) != Z_OK)
 			BUG("deflateSetHeader() called too late");
-#endif
 		gzstream.next_out = outbuf;
 		gzstream.avail_out = sizeof(outbuf);
 
diff --git a/compat/zlib-compat.h b/compat/zlib-compat.h
index 96a08811a98ff7fa057f5682a5303a06cef40cd1..2690bfce41caab2e9af7a09663d620f0ee5136a0 100644
--- a/compat/zlib-compat.h
+++ b/compat/zlib-compat.h
@@ -7,4 +7,17 @@
 # define deflateBound(c,s)  ((s) + (((s) + 7) >> 3) + (((s) + 63) >> 6) + 11)
 #endif
 
+#if ZLIB_VERNUM < 0x1221
+struct gz_header_s {
+	int os;
+};
+
+static int deflateSetHeader(z_streamp strm, struct gz_header_s *head)
+{
+	(void)(strm);
+	(void)(head);
+	return Z_OK;
+}
+#endif
+
 #endif /* COMPAT_ZLIB_H */

-- 
2.48.0.rc2.279.g1de40edade.dirty