On Fri, Jun 26, 2020 at 12:30:29PM +0000, Derrick Stolee via GitGitGadget wrote:
> From: Derrick Stolee <dstolee@xxxxxxxxxxxxx>
>
> The get_bloom_filter() method is a bit complicated in some parts where
> it does not need to be. In particular, it needs to return a NULL filter
> only when compute_if_not_present is zero AND the filter data cannot be
> loaded from a commit-graph file. This currently happens by accident
> because the commit-graph does not load changed-path Bloom filters from
> an existing commit-graph when writing a new one. This will change in a
> later patch.
>
> Also clean up some style issues while we are here.
>
> Helped-by: René Scharfe <l.s.r@xxxxxx>
> Signed-off-by: Derrick Stolee <dstolee@xxxxxxxxxxxxx>
> ---
> bloom.c | 14 ++++++--------
> 1 file changed, 6 insertions(+), 8 deletions(-)
>
> diff --git a/bloom.c b/bloom.c
> index c38d1cff0c..2af5389795 100644
> --- a/bloom.c
> +++ b/bloom.c
> @@ -186,7 +186,7 @@ struct bloom_filter *get_bloom_filter(struct repository *r,
> struct diff_options diffopt;
> int max_changes = 512;
>
> - if (bloom_filters.slab_size == 0)
> + if (!bloom_filters.slab_size)
> return NULL;
>
> filter = bloom_filter_slab_at(&bloom_filters, c);
> @@ -194,16 +194,14 @@ struct bloom_filter *get_bloom_filter(struct repository *r,
> if (!filter->data) {
> load_commit_graph_info(r, c);
> if (c->graph_pos != COMMIT_NOT_FROM_GRAPH &&
> - r->objects->commit_graph->chunk_bloom_indexes) {
> - if (load_bloom_filter_from_graph(r->objects->commit_graph, filter, c))
> - return filter;
> - else
> - return NULL;
> - }
> + r->objects->commit_graph->chunk_bloom_indexes)
> + load_bloom_filter_from_graph(r->objects->commit_graph, filter, c);
> }
>
> - if (filter->data || !compute_if_not_present)
> + if (filter->data)
> return filter;
> + if (!compute_if_not_present)
> + return NULL;
Some callers of get_bloom_filter() invoke it with
compute_if_not_present=0, but are not prepared to handle a NULL return
value and dereference it right away:
write_graph_chunk_bloom_indexes():
struct bloom_filter *filter = get_bloom_filter(ctx->r, *list, 0);
cur_pos += filter->len;
write_graph_chunk_bloom_data():
struct bloom_filter *filter = get_bloom_filter(ctx->r, *list, 0);
display_progress(progress, ++i);
hashwrite(f, filter->data, filter->len * sizeof(unsigned char));
I don't know whether this was an issue before, but I didn't really
tried. Unfortunately, starting with this patch this causes
segmentation faults basically in all real repositories I use for
testing.
expecting success of 9999.1 'test':
for i in $(test_seq 1 513)
do
>file-$i || return 1
done &&
git add file-* &&
git commit -q -m one &&
git commit-graph write --reachable --changed-paths
Segmentation fault
not ok 1 - test
Program received signal SIGSEGV, Segmentation fault.
0x0000000000515848 in write_graph_chunk_bloom_indexes (f=0x9fe650,
ctx=0x9d2000) at commit-graph.c:1101
1101 cur_pos += filter->len;
(gdb) print filter
$1 = (struct bloom_filter *) 0x0
> repo_diff_setup(r, &diffopt);
> diffopt.flags.recursive = 1;
> --
> gitgitgadget
>
