split-index: fix memory leak in move_cache_to_base_index()

In `move_cache_to_base_index()` we move the index cache of the main
index into the split index, which is used when writing a shared index.
But we don't release the old split index base in case we already had a
split index before this operation, which can thus leak memory.

Plug the leak by releasing the previous base.

Signed-off-by: Patrick Steinhardt <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: pks-t

split-index.c

@@ -97,7 +97,11 @@ void move_cache_to_base_index(struct index_state *istate)
 		mem_pool_combine(istate->ce_mem_pool, istate->split_index->base->ce_mem_pool);
 	}
 
-	ALLOC_ARRAY(si->base, 1);
+	if (si->base)
+		release_index(si->base);
+	else
+		ALLOC_ARRAY(si->base, 1);
+
 	index_state_init(si->base, istate->repo);
 	si->base->version = istate->version;
 	/* zero timestamp disables racy test in ce_write_index() */

t/t1700-split-index.sh

@@ -5,6 +5,7 @@ test_description='split index mode tests'
 GIT_TEST_DEFAULT_INITIAL_BRANCH_NAME=main
 export GIT_TEST_DEFAULT_INITIAL_BRANCH_NAME
 
+TEST_PASSES_SANITIZE_LEAK=true
 . ./test-lib.sh
 
 # We need total control of index splitting here