submodule-config: avoid memory leak

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>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/submodule-config.c b/submodule-config.c
index ce3beaf5d4f0d648310acc39a76e31d67a3a40c8..51ecbe901ec42980b0a81685ec1529bd20cc205b 100644 (file)
--- 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);