From 6ba0be16391697bdaab7d8f836b66921977d5474 Mon Sep 17 00:00:00 2001 From: Keith Randall Date: Sat, 16 Nov 2019 07:12:53 -0800 Subject: [PATCH] hash/maphash: mark call into runtime hash function as not escaping This allows maphash.Hash to be allocated on the stack for typical uses. Fixes #35636 Change-Id: I8366507d26ea717f47a9fb46d3bd69ba799845ac Reviewed-on: https://go-review.googlesource.com/c/go/+/207444 Run-TryBot: Keith Randall TryBot-Result: Gobot Gobot Reviewed-by: Brad Fitzpatrick --- src/hash/maphash/maphash.go | 1 + test/escape_hash_maphash.go | 19 +++++++++++++++++++ 2 files changed, 20 insertions(+) create mode 100644 test/escape_hash_maphash.go diff --git a/src/hash/maphash/maphash.go b/src/hash/maphash/maphash.go index 9b6c0cfb99..3f406e9db6 100644 --- a/src/hash/maphash/maphash.go +++ b/src/hash/maphash/maphash.go @@ -193,6 +193,7 @@ func rthash(b []byte, seed uint64) uint64 { } //go:linkname runtime_memhash runtime.memhash +//go:noescape func runtime_memhash(p unsafe.Pointer, seed, s uintptr) uintptr // Sum appends the hash's current 64-bit value to b. diff --git a/test/escape_hash_maphash.go b/test/escape_hash_maphash.go new file mode 100644 index 0000000000..f8dcc5450d --- /dev/null +++ b/test/escape_hash_maphash.go @@ -0,0 +1,19 @@ +// errorcheck -0 -m -l + +// Copyright 2019 The Go Authors. All rights reserved. +// Use of this source code is governed by a BSD-style +// license that can be found in the LICENSE file. + +// Test escape analysis for hash/maphash. + +package escape + +import ( + "hash/maphash" +) + +func f() { + var x maphash.Hash // should be stack allocatable + x.WriteString("foo") + x.Sum64() +}