On Mon, Feb 27, 2017 at 10:59:15PM -0800, Linus Torvalds wrote:
> I saw that somebody is actually looking at doing this "well" - by
> doing it in many smaller steps. I tried. I gave up. The "unsigned char
> *sha1" model is so ingrained that doing it incrementally just seemed
> like a lot of pain. But it might be the right approach.
That somebody is brian carlson, cc'd.
> which is pretty nasty. The good news is that my patch passes all the
> tests, and while it's big it's mostly very very mindless, and a lot of
> it looks like cleanups, and the lines are generally shorter, eg
>
> - const unsigned char *mb = result->item->object.oid.hash;
> - if (!hashcmp(mb, current_bad_oid->hash)) {
>
> turns into
>
> + const hash_t *mb = &result->item->object.oid;
> + if (!hashcmp(mb, current_bad_oid)) {
>
> but I ended up also renaming a lot of common "sha1" as "hash", which
> adds to the noise in that patch.
I think the preimage there is worse than it ought to be because it's
mid-transition. "struct object" has an object_id, but the rest of the
function hasn't been converted yet. So ultimately it should be:
const struct object_id *mb = &result->item->object.oid;
if (!oidcmp(mb, current_bad_oid))
It looks like you stuck your "hash_t" inside "struct object_id", which I
think is redundant. They're both trying to solve the same problem.
> NOTE! It doesn't actually _fix_ the SHA1-centricity in any way, but it
> makes it a bit more obvious where the bigger problems are. Not that
> anybody would be surprised by what they are, but as part of writing
> the patch it did kind of pinpoint most of them, and about 30 of those
> new lines are added
>
> /* FIXME! Hardcoded hash sizes */
> /* FIXME! Lots of fixed-size hashes */
> /* FIXME! Fixed 20-byte hash usage */
Yeah, a lot of brian's patches have been focused around the fixing the
related size assumptions. We've got GIT_SHA1_HEXSZ which doesn't solve
the problem, but at least makes it easy to find. And a big improvement
in the most recent series is a parse_oid() function that lets you parse
object-ids left-to-right without knowing the size up front. So things
like:
if (len > 82 &&
!get_sha1_hex(buf, sha1_a) &&
get_sha1_hex(buf + 41, sha1_b))
becomes more like:
if (parse_oid(p, oid_a, &p) && *p++ == ' ' &&
parse_oid(p, oid_b, &p) && *p++ == '\n')
Still, if you've done more conversion, it's probably worth showing it
publicly. It might not end up used, but it may serve as a reference
later.
> And as part of the type safety, I do think I may have found a bug:
>
> show_one_mergetag():
>
> strbuf_addf(&verify_message, "tag %s names a non-parent %s\n",
> tag->tag, tag->tagged->oid.hash);
>
> note how it prints out the "non-parent %s", but that's a SHA1 hash
> that hasn't been converted to hex. Hmm?
Yeah, that's definitely a bug. I'm surprised that -Wformat doesn't
complain, but I guess we'd need -Wformat-signedness (which triggers
quite a lot of warnings related to "int"). It's especially bad for "%x",
which is implicitly unsigned.
-Peff