[PATCH] repack: free geometry struct

From: Jeff King <peff@peff.net>
Date: Aug 8, 2023, 18:50 UTC
Message-ID: <20230808185023.GA3498623@coredump.intra.peff.net>

When the program is ending, we call clear_pack_geometry() to free any resources in the pack_geometry struct. But the struct itself is allocated on the heap, and leak-checkers will complain about the resulting small leak.

This one was marked by Coverity as a "new" leak, though it has existed since 0fabafd0b9 (builtin/repack.c: add '--geometric' option, 2021-02-22). This might be because recent unrelated changes in the file confused it about what is new and what is not. But regardless, it is worth addressing.

We can fix it easily by free-ing the struct. We'll convert our "clear" function to "free", since the allocation happens in the matching init() function (though since there is only one call to each, and the struct is local to this file, it's mostly academic).

Another option would be to put the struct on the stack rather than the heap. However, this gets tricky, as we check the pointer against NULL in several places to decide whether we're in geometric mode.

Signed-off-by: Jeff King <peff@peff.net>
---
I did actually put together the "put it on the stack" patch, which swaps
out:

  if (geometry)

for:

  if (geometric_factor)

to get around the NULL checks. But besides being noisy for little gain, it ends up with some subtle gotchas, because we pass "&geometry" into some functions which don't have access to "geometric_factor" (so now extra call-sites have to keep track of "is this struct valid enough to pass").

 builtin/repack.c | 8 +++-----
 1 file changed, 3 insertions(+), 5 deletions(-)

diff --git a/builtin/repack.c b/builtin/repack.c
index aea5ca9d44..97051479e4 100644
--- a/builtin/repack.c
+++ b/builtin/repack.c
@@ -492,15 +492,13 @@ static struct packed_git *get_preferred_pack(struct pack_geometry *geometry)
 	return NULL;
 }
 
-static void clear_pack_geometry(struct pack_geometry *geometry)
+static void free_pack_geometry(struct pack_geometry *geometry)
 {
 	if (!geometry)
 		return;
 
 	free(geometry->pack);
-	geometry->pack_nr = 0;
-	geometry->pack_alloc = 0;
-	geometry->split = 0;
+	free(geometry);
 }
 
 struct midx_snapshot_ref_data {
@@ -1228,7 +1226,7 @@ int cmd_repack(int argc, const char **argv, const char *prefix)
 	string_list_clear(&names, 1);
 	string_list_clear(&existing_nonkept_packs, 0);
 	string_list_clear(&existing_kept_packs, 0);
-	clear_pack_geometry(geometry);
+	free_pack_geometry(geometry);
 
 	return ret;
 }

-- 
2.42.0.rc0.376.g66bfc4f195