Stephan Beyer <s-beyer@xxxxxxx> writes:
> diff --git a/fast-import.c b/fast-import.c
> index b44d6a467e..58f73f9105 100644
> --- a/fast-import.c
> +++ b/fast-import.c
> @@ -903,7 +903,8 @@ static int store_object(
> struct object_entry *e;
> unsigned char hdr[96];
> struct object_id oid;
> - unsigned long hdrlen, deltalen;
> + unsigned long hdrlen;
> + unsigned long deltalen = 0;
> git_hash_ctx c;
> git_zstream s;
[in my attempt to imitate Réne...]
In this function, deltalen is used only when delta != NULL, i.e.
if (delta) {
s.next_in = delta;
s.avail_in = deltalen;
} else {
s.next_in = (void *)dat->buf;
s.avail_in = dat->len;
}
...
if (delta) {
...
hdrlen = encode_in_pack_object_header(hdr, sizeof(hdr),
OBJ_OFS_DELTA, deltalen);
...
Could delta become non-NULL without deltalen getting set? We see
these before all uses of delta/deltalen in this function.
if (last && last->data.len && last->data.buf && last->depth < max_depth
&& dat->len > the_hash_algo->rawsz) {
delta_count_attempts_by_type[type]++;
delta = diff_delta(last->data.buf, last->data.len,
dat->buf, dat->len,
&deltalen, dat->len - the_hash_algo->rawsz);
} else
delta = NULL;
If diff_delta() returns non-NULL without touching deltalen, we'd be
in trouble. We see this in delta.h
static inline void *
diff_delta(const void *src_buf, unsigned long src_bufsize,
const void *trg_buf, unsigned long trg_bufsize,
unsigned long *delta_size, unsigned long max_delta_size)
{
struct delta_index *index = create_delta_index(src_buf, src_bufsize);
if (index) {
void *delta = create_delta(index, trg_buf, trg_bufsize,
delta_size, max_delta_size);
free_delta_index(index);
return delta;
}
return NULL;
}
so the question is if create_delta() can return non-NULL without
touching delta_size. In diff-delta.c::create_delta(), *delta_size
is assigned once at the very end, when the function returns a
pointer to an allocated memory 'out'. All the "return" statement
other than that last one literally returns "NULL".
So it seems that this is a case the compiler getting confused.
