tree efa33cada91b19c1deb215c8b73d8efb669573a2
parent 274ed2ea9d496f75030f849c4259b35ecb4d35c1
author Hans Boehm <hboehm@google.com> 1544133079 -0800
committer Hans Boehm <hboehm@google.com> 1544212220 -0800

Fix ModifyCardsAtomic comment

The function doesn't behave as it was previously specified. Its
actual semantics are arguably ugly, but that doesn't really seem to
break anything. Just specify what it really does, and add DCHECK
to validate previously undocumented assumption.

Deduplicate the comment.

Update card_table_test, so it no longer invokes ModifyCardsAtomic
with a now disallowed visitor. This was OK, because it's applied
to a card table containing no zeroes, and hence the misbehaving
visitor didn't matter. Now we check.

Test: Treehugger.
Change-Id: Id1ba1cb39c709a33c362d4e386ddcb065bd39049