refdb and odb backends must provide `free` function

As refdb and odb backends can be allocated by client code, libgit2
can’t know whether an alternative memory allocator was used, and thus
should not try to call `git__free` on those objects.

Instead, odb and refdb backend implementations must always provide
their own `free` functions to ensure memory gets freed correctly.

2 files changed, 6 insertions, 2 deletions

diff --git a/include/git2/sys/odb_backend.h b/include/git2/sys/odb_backend.h
index fe102ff3c..e423a9236 100644
--- a/include/git2/sys/odb_backend.h
+++ b/include/git2/sys/odb_backend.h
@@ -83,6 +83,10 @@ struct git_odb_backend {
 		git_odb_writepack **, git_odb_backend *, git_odb *odb,
 		git_transfer_progress_cb progress_cb, void *progress_payload);
 
+	/**
+	 * Frees any resources held by the odb (including the `git_odb_backend`
+	 * itself). An odb backend implementation must provide this function.
+	 */
 	void (* free)(git_odb_backend *);
 };
 
diff --git a/include/git2/sys/refdb_backend.h b/include/git2/sys/refdb_backend.h
index 01fce8009..5129ad84a 100644
--- a/include/git2/sys/refdb_backend.h
+++ b/include/git2/sys/refdb_backend.h
@@ -130,8 +130,8 @@ struct git_refdb_backend {
 	int (*ensure_log)(git_refdb_backend *backend, const char *refname);
 
 	/**
-	 * Frees any resources held by the refdb.  A refdb implementation may
-	 * provide this function; if it is not provided, nothing will be done.
+	 * Frees any resources held by the refdb (including the `git_refdb_backend`
+	 * itself). A refdb backend implementation must provide this function.
 	 */
 	void (*free)(git_refdb_backend *backend);