// message and calls log.Fatal.
func (c *Client) checkTrees(older tlog.Tree, olderNote []byte, newer tlog.Tree, newerNote []byte) error {
	thr := tlog.TileHashReader(newer, &c.tileReader)
	h, err := tlog.TreeHash(older.N, thr)
	if err != nil {
		if older.N == newer.N {
			return fmt.Errorf("checking tree#%d: %v", older.N, err)
		}
		return fmt.Errorf("checking tree#%d against tree#%d: %v", older.N, newer.N, err)
	}

			"pcvalueCacheKey",
			"rand32",
			"readUnaligned32",
			"readUnaligned64",
			"releasem",
			"roundupsize",
			"stackmapdata",
			"stringStructOf",
			"subtract1",
			"subtractb",
			"tophash",
			"(*bmap).keys",
			"(*bmap).overflow",
			"(*waitq).enqueue",
			"funcInfo.entry",

			// GC-related ones
			"cgoInRange",
			"gclinkptr.ptr",
			"guintptr.ptr",
			"heapBitsSlice",

			for i := 0; i < abi.MapBucketCount; i++ {
				if b.tophash[i] != emptyRest {
					n++
				}
			}
		}
		k := 0
		for b := b0; b != nil; b = b.overflow(t) {
			for i := 0; i < abi.MapBucketCount; i++ {
				if k < n && b.tophash[i] == emptyRest {
					panic("early emptyRest")
				}
				if k >= n && b.tophash[i] != emptyRest {
					panic("late non-emptyRest")
				}

					if bucket >= 2 ** (B - 1):
						continue    # already did old bucket
					bp = oldbp
			while bp:
				b = bp.dereference()
				for i in xrange(MapBucketCount):
					if b['tophash'][i] != 0:
						k = b['keys'][i]
						v = b['values'][i]
						if flags & 1:
							k = k.dereference()
						if flags & 2:
							v = v.dereference()
						yield str(cnt), k
						yield str(cnt + 1), v