diff mercurial/cext/revlog.c @ 43847:49fa0b31ee1d

cext-revlog: fixed  __delitem__ for uninitialized nodetree

This is a bug in a code path that's seldom used, because in practice
(at least in the whole test suite), calls to `del index[i:j]` currently
just don't happen before the nodetree has been initialized.
However, in our current work to replace the nodetree by a Rust implementation,
this is of course systematic.

In `index_slice_del()`, if the slice start is smaller than `self->length`,
the whole of `self->added` has to be cleared.

Before this change, the clearing was done only by the call to
`index_invalidate_added(self, 0)`, that happens only for initialized
nodetrees. Hence the removal was effective only from `start` to `self->length`.

The consequence is index corruption, with bogus results in subsequent calls,
and in particular errors such as `ValueError("parent out of range")`, due to
the fact that parents of entries in `self->added` are now just invalid.

This is detected by the rebase tests, under conditions that the nodetree
of revlog.c is never initialized. The provided specific test is more direct.

Differential Revision: https://phab.mercurial-scm.org/D7603

--- a/mercurial/cext/revlog.c	Wed Nov 20 13:03:22 2019 -0500
+++ b/mercurial/cext/revlog.c	Thu Dec 05 20:41:23 2019 +0100
@@ -2522,7 +2522,10 @@
 				index_invalidate_added(self, 0);
 			if (self->ntrev > start)
 				self->ntrev = (int)start;
+		} else if (self->added) {
+			Py_CLEAR(self->added);
 		}
+
 		self->length = start;
 		if (start < self->raw_length) {
 			if (self->cache) {