From: Keith Randall <khr@golang.org>
Date: Fri, 18 Aug 2017 06:13:57 +0000 (-0700)
Subject: runtime: no need to protect key/value increments against end of bucket
X-Git-Tag: go1.10beta1~1466
X-Git-Url: http://www.git.cypherpunks.su/?a=commitdiff_plain;h=77871cc664b3a87e4972c874369e2ade79038d76;p=gostls13.git

runtime: no need to protect key/value increments against end of bucket

After the key and value arrays, we have an overflow pointer.
So there's no way a past-the-end key or value pointer could point
past the end of the containing bucket.

So we don't need this additional protection.

Update #21459

Change-Id: I7726140033b06b187f7a7d566b3af8cdcaeab0b0
Reviewed-on: https://go-review.googlesource.com/56772
Run-TryBot: Keith Randall <khr@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Martin Möhrmann <moehrmann@google.com>
Reviewed-by: Josh Bleecher Snyder <josharian@gmail.com>
Reviewed-by: Avelino <t@avelino.xxx>
---

diff --git a/src/runtime/hashmap.go b/src/runtime/hashmap.go
index 28ea376cf4..f39fb7d3bf 100644
--- a/src/runtime/hashmap.go
+++ b/src/runtime/hashmap.go
@@ -1119,12 +1119,12 @@ func evacuate(t *maptype, h *hmap, oldbucket uintptr) {
 					typedmemmove(t.elem, dst.v, v)
 				}
 				dst.i++
-				// If we're at the end of the bucket, don't update k/v,
-				// to avoid pointers pointing past the end of the bucket.
-				if dst.i < bucketCnt {
-					dst.k = add(dst.k, uintptr(t.keysize))
-					dst.v = add(dst.v, uintptr(t.valuesize))
-				}
+				// These updates might push these pointers past the end of the
+				// key or value arrays.  That's ok, as we have the overflow pointer
+				// at the end of the bucket to protect against pointing past the
+				// end of the bucket.
+				dst.k = add(dst.k, uintptr(t.keysize))
+				dst.v = add(dst.v, uintptr(t.valuesize))
 			}
 		}
 		// Unlink the overflow buckets & clear key/value to help GC.