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list-objects-filter: use empty string instead of NULL for sparse "base"

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We use add_excludes_from_blob_to_list() to parse a sparse blob. Since
we don't have a base path, we pass NULL and 0 for the base and baselen,
respectively. But the rest of the exclude code passes a literal empty
string instead of NULL for this case. And indeed, we eventually end up
with match_pathname() calling fspathncmp(), which then calls the system
strncmp(path, base, baselen).

This works on many platforms, which notice that baselen is 0 and do not
look at the bytes of "base" at all. But it does violate the C standard,
and building with SANITIZE=undefined will complain. You can also see it
by instrumenting fspathncmp like this:

	diff --git a/dir.c b/dir.c
	index d021c908e5..4bb3d3ec96 100644
	--- a/dir.c
	+++ b/dir.c
	@@ -71,6 +71,8 @@ int fspathcmp(const char *a, const char *b)

	 int fspathncmp(const char *a, const char *b, size_t count)
	 {
	+	if (!a || !b)
	+		BUG("null fspathncmp arguments");
	 	return ignore_case ? strncasecmp(a, b, count) : strncmp(a, b, count);
	 }

We could perhaps be more defensive in match_pathname(), but even if we
did so, it makes sense for this code to match the rest of the exclude
callers.

Signed-off-by: Jeff King <peff@peff.net>
Acked-by: Jeff Hostetler <jeffhost@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This commit is contained in:
Jeff King 2019-09-15 12:51:56 -04:00 committed by Junio C Hamano
parent cf34337f98
commit a4cafc7379
1 changed files with 1 additions and 1 deletions
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2
list-objects-filter.c
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@ -472,7 +472,7 @@ static void *filter_sparse_oid__init(
die(_("unable to access sparse blob in '%s'"),
filter_options->sparse_oid_name);
d->omits = omitted;
if (add_excludes_from_blob_to_list(&sparse_oid, NULL, 0, &d->el) < 0)
if (add_excludes_from_blob_to_list(&sparse_oid, "", 0, &d->el) < 0)
die(_("unable to parse sparse filter data in %s"),
oid_to_hex(&sparse_oid));