Re: [PATCH] pack-objects: lazily set up "struct rev_info", don't leak
- From
Derrick Stolee <derrickstolee@github.com>
- Date
- Mar 25, 2022, 19:08 UTC
- Message-ID
- <d90bb9c8-3155-ca5f-8363-154876a7ad0a@github.com>
- In-Reply-To
- <220325.86mthdlx59.gmgdl@evledraar.gmail.com>
On 3/25/2022 1:34 PM, Ævar Arnfjörð Bjarmason wrote:
Show 27 quoted lines
>
> On Fri, Mar 25 2022, Derrick Stolee wrote:
>
>> On 3/25/2022 12:00 PM, Ævar Arnfjörð Bjarmason wrote:
>>>> +struct rev_info_maybe_empty {
>>>> + int has_revs;
>>>> + struct rev_info revs;
>>>> +};
>>
>> Thinking about this a second time, perhaps it would be best to add
>> an "unsigned initialized:1;" to struct rev_info so we can look at
>> such a struct and know whether or not repo_init_revisions() has
>> been run or not. Avoids the custom struct and unifies a few things.
>>
>> In particular, release_revisions() could choose to do nothing if
>> revs->initialized is false.
>
> This plan won't work because that behavior is both undefined per the
> standard, and something that's wildly undefined in practice.
>
> I.e. we initialize it on the stack, so it'll point to uninitialized
> memory, sometimes that bit will be 0, sometimes 1...
>
> If you mean just initialize it to { 0 } or whatever that would work,
> yes, but if we're going to refactor all the callers to do that we might
> as well refactor the few missing bits that would be needed to initialize
> it statically, and drop the dynamic by default initialization...Yes, I was assuming that we initialize all structs to all-zero, but the existing failure to do this will cause such a change too large for this issue.
Show 8 quoted lines
> But FWIW I think a much more obvious thing to do overall would be to > skip the whole "filter bust me in rev_info" refactoring part of your > series and just add a trivial list_objects_filter_copy_attach() method, > or do it inline with memcpy/memset. > > I.e. to not touch the "filter" etc. callback stuff at all, still pass it > to get_object_list(). Can't 2/5 and 3/5 in your series be replaced by > this simpler and smaller change?:
> - list_objects_filter_copy(&revs.filter, &filter_options); > + /* attach our CLI --filter to rev_info's filter */ > + memcpy(&revs.filter, filter, sizeof(*filter)); > + memset(filter, 0, sizeof(*filter));
Here, you are removing a deep copy with a shallow copy. After this, freeing the arrays within revs.filter would cause a double-free when freeing the arrays in the original filter_options.
If you went this way, then you could do a s/&filter_options/filter/ in the existing line.
Show 22 quoted lines
> /* make sure shallows are read */
> is_repository_shallow(the_repository);
> @@ -3872,6 +3873,7 @@ int cmd_pack_objects(int argc, const char **argv, const char *prefix)
> int rev_list_index = 0;
> int stdin_packs = 0;
> struct string_list keep_pack_list = STRING_LIST_INIT_NODUP;
> + struct list_objects_filter_options filter_options = { 0 };
> struct option pack_objects_options[] = {
> OPT_SET_INT('q', "quiet", &progress,
> N_("do not show progress meter"), 0),
> @@ -4154,7 +4156,7 @@ int cmd_pack_objects(int argc, const char **argv, const char *prefix)
> } else if (!use_internal_rev_list) {
> read_object_list_from_stdin();
> } else {
> - get_object_list(rp.nr, rp.v);
> + get_object_list(rp.nr, rp.v, &filter_options);
> }
> cleanup_preferred_base();
> if (include_tag && nr_result)
>
> And even most of that could be omitted by not removing the global
> "static struct" since pack-objects is a one-off anyway ... :)Even if you fix the deep/shallow copy above, you still need to clean up the filter in two places.
Thanks, -Stolee