Re: [PATCH v5] alloc: fix dangling pointer in alloc_state cleanup
Jeff King <peff@peff.net> writes:
Show 14 quoted lines
> It's probably not worth going back and forth on this too much, but I
> thought the happy medium was:
>
> if (!s)
> return;
>
> That is, it is perfectly reasonable and friendly for it to be a noop to
> free-and-null a NULL value (either never initialized, or already freed).
> The overkill was worrying about whether somebody passed in a NULL
> double-pointer. I.e., doing:
>
> alloc_state_free_and_null(&foo);
>
> is reasonable and should be idempotent
... when foo == NULL, e.g., after alloc_state_free_and_null(&foo) has just successfully returned?
I can by that argument with the reasoning in the updated log message below. Does it good to everybody?
Thanks.
--- >8 ---
From: ノウラ | Flare <nouraellm@gmail.com>
Subject: [PATCH] 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>
---
alloc.c | 10 ++++++++--
alloc.h | 4 ++--
object.c | 26 ++++++++++----------------
3 files changed, 20 insertions(+), 20 deletions(-)
Show changes to 3 files +20 −20
alloc.c, alloc.h, object.c
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)
diff --git a/alloc.h b/alloc.h
index 3f4a0ad310..87a47a9709 100644
--- a/alloc.h
+++ b/alloc.h
@@ -14,7 +14,7 @@ void *alloc_commit_node(struct repository *r);
void *alloc_tag_node(struct repository *r);
void *alloc_object_node(struct repository *r);
-struct alloc_state *allocate_alloc_state(void);
-void clear_alloc_state(struct alloc_state *s);
+struct alloc_state *alloc_state_alloc(void);
+void alloc_state_free_and_null(struct alloc_state **s_);
#endif
diff --git a/object.c b/object.c
index c1553ee433..986114a6db 100644
--- a/object.c
+++ b/object.c
@@ -517,12 +517,11 @@ struct parsed_object_pool *parsed_object_pool_new(struct repository *repo)
memset(o, 0, sizeof(*o));
o->repo = repo;
- o->blob_state = allocate_alloc_state();
- o->tree_state = allocate_alloc_state();
- o->commit_state = allocate_alloc_state();
- o->tag_state = allocate_alloc_state();
- o->object_state = allocate_alloc_state();
-
+ o->blob_state = alloc_state_alloc();
+ o->tree_state = alloc_state_alloc();
+ o->commit_state = alloc_state_alloc();
+ o->tag_state = alloc_state_alloc();
+ o->object_state = alloc_state_alloc();
o->is_shallow = -1;
CALLOC_ARRAY(o->shallow_stat, 1);
@@ -573,16 +572,11 @@ void parsed_object_pool_clear(struct parsed_object_pool *o)
o->buffer_slab = NULL;
parsed_object_pool_reset_commit_grafts(o);
- clear_alloc_state(o->blob_state);
- clear_alloc_state(o->tree_state);
- clear_alloc_state(o->commit_state);
- clear_alloc_state(o->tag_state);
- clear_alloc_state(o->object_state);
+ alloc_state_free_and_null(&o->blob_state);
+ alloc_state_free_and_null(&o->tree_state);
+ alloc_state_free_and_null(&o->commit_state);
+ alloc_state_free_and_null(&o->tag_state);
+ alloc_state_free_and_null(&o->object_state);
stat_validity_clear(o->shallow_stat);
- FREE_AND_NULL(o->blob_state);
- FREE_AND_NULL(o->tree_state);
- FREE_AND_NULL(o->commit_state);
- FREE_AND_NULL(o->tag_state);
- FREE_AND_NULL(o->object_state);
FREE_AND_NULL(o->shallow_stat);
}
--
2.51.0-314-g9a15cfd6dc
ノウラ | Flare via GitGitGadget
