alloc: fix dangling pointer in alloc_state cleanup

All callers of clear_alloc_state() immediately free what they
cleared, so currently it does not hurt anybody that the
alloc_state is left in an unreusable state, but it is an
error-prone API. Replace it with a new function that clears but
in addition frees the structure, as well as NULLing the pointer
that points at it and adjust existing callers.

As it is a moral equivalent of FREE_AND_NULL(), except that what it
frees has internal structure that needs to be cleaned, allow the
helper to be called twice in a row, by making a call with a pointer
to a pointer variable that already is NULLed.

While at it, rename allocate_alloc_state() and name the new
function alloc_state_free_and_null(), to follow more closely the
function naming convention specified in the CodingGuidelines
(namely, functions about S are named with S_ prefix and then
verb).

Signed-off-by: ノウラ | Flare <nouraellm@gmail.com>
Helped-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 8 insertions, 2 deletions

diff --git a/alloc.c b/alloc.c
index 377e80f5dd..533a045c2a 100644
--- a/alloc.c
+++ b/alloc.c
@@ -36,19 +36,25 @@ struct alloc_state {
 	int slab_nr, slab_alloc;
 };
 
-struct alloc_state *allocate_alloc_state(void)
+struct alloc_state *alloc_state_alloc(void)
 {
 	return xcalloc(1, sizeof(struct alloc_state));
 }
 
-void clear_alloc_state(struct alloc_state *s)
+void alloc_state_free_and_null(struct alloc_state **s_)
 {
+	struct alloc_state *s = *s_;
+
+	if (!s)
+		return;
+
 	while (s->slab_nr > 0) {
 		s->slab_nr--;
 		free(s->slabs[s->slab_nr]);
 	}
 
 	FREE_AND_NULL(s->slabs);
+	FREE_AND_NULL(*s_);
 }
 
 static inline void *alloc_node(struct alloc_state *s, size_t node_size)