[PATCH 05/11] submodule-config: avoid memory leak

From: Johannes Schindelin via GitGitGadget <gitgitgadget@gmail.com>
Date: Jun 15, 2022, 23:35 UTC
Message-ID: <591166e07d87fdb5efc2769d3e2963e3f0412720.1655336146.git.gitgitgadget@gmail.com>
In-Reply-To: <pull.1264.git.1655336146.gitgitgadget@gmail.com>

From: Johannes Schindelin <johannes.schindelin@gmx.de>

In 961b130d20c9 (branch: add --recurse-submodules option for branch creation, 2022-01-28), a funny pattern was introduced where first some struct is `xmalloc()`ed, then we resize an array whose element type is the same struct, and then the first struct's contents are copied into the last element of that array.

Crucially, the `xmalloc()`ed memory never gets released.

Let's avoid that memory leak and that memory allocation dance altogether by first reallocating the array, then using a pointer to the last array element to go forward.

Reported by Coverity.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
---
 submodule-config.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/submodule-config.c b/submodule-config.c
index ce3beaf5d4f..51ecbe901ec 100644
--- a/submodule-config.c
+++ b/submodule-config.c
@@ -756,7 +756,10 @@ static void traverse_tree_submodules(struct repository *r,
 
 		if (S_ISGITLINK(name_entry->mode) &&
 		    is_tree_submodule_active(r, root_tree, tree_path)) {
-			st_entry = xmalloc(sizeof(*st_entry));
+			ALLOC_GROW(out->entries, out->entry_nr + 1,
+				   out->entry_alloc);
+			st_entry = &out->entries[out->entry_nr++];
+
 			st_entry->name_entry = xmalloc(sizeof(*st_entry->name_entry));
 			*st_entry->name_entry = *name_entry;
 			st_entry->submodule =
@@ -766,9 +769,6 @@ static void traverse_tree_submodules(struct repository *r,
 						root_tree))
 				FREE_AND_NULL(st_entry->repo);
 
-			ALLOC_GROW(out->entries, out->entry_nr + 1,
-				   out->entry_alloc);
-			out->entries[out->entry_nr++] = *st_entry;
 		} else if (S_ISDIR(name_entry->mode))
 			traverse_tree_submodules(r, root_tree, tree_path,
 						 &name_entry->oid, out);

-- 
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