From ac40c9872f6e8ef095dcc6ee556236782eee4f76 Mon Sep 17 00:00:00 2001 From: Keith Randall Date: Mon, 13 Sep 2021 09:17:22 -0700 Subject: reflect: fix _faststr optimization MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit CL 345486 introduced an optimization to reflect's map accesses which is not quite correct. We can't use the optimized code if the value type is >128 bytes. See cmd/compile/internal/walk/walk.go:mapfast Fixes #48357 Change-Id: I8e3c7858693083dd4393a8de48ca5fa47bab66f2 Reviewed-on: https://go-review.googlesource.com/c/go/+/349593 Trust: Keith Randall Trust: Joe Tsai Trust: Josh Bleecher Snyder Trust: Martin Möhrmann Run-TryBot: Keith Randall Run-TryBot: Joe Tsai Reviewed-by: Joe Tsai Reviewed-by: Josh Bleecher Snyder Reviewed-by: Martin Möhrmann TryBot-Result: Go Bot --- src/reflect/value.go | 4 ++-- test/fixedbugs/issue48357.go | 20 ++++++++++++++++++++ 2 files changed, 22 insertions(+), 2 deletions(-) create mode 100644 test/fixedbugs/issue48357.go diff --git a/src/reflect/value.go b/src/reflect/value.go index 6e9aaabe8a..bc48a76ce6 100644 --- a/src/reflect/value.go +++ b/src/reflect/value.go @@ -1517,7 +1517,7 @@ func (v Value) MapIndex(key Value) Value { // of unexported fields. var e unsafe.Pointer - if key.kind() == String && tt.key.Kind() == String { + if key.kind() == String && tt.key.Kind() == String && tt.elem.size <= maxValSize { k := *(*string)(key.ptr) e = mapaccess_faststr(v.typ, v.pointer(), k) } else { @@ -2128,7 +2128,7 @@ func (v Value) SetMapIndex(key, elem Value) { key.mustBeExported() tt := (*mapType)(unsafe.Pointer(v.typ)) - if key.kind() == String && tt.key.Kind() == String { + if key.kind() == String && tt.key.Kind() == String && tt.elem.size <= maxValSize { k := *(*string)(key.ptr) if elem.typ == nil { mapdelete_faststr(v.typ, v.pointer(), k) diff --git a/test/fixedbugs/issue48357.go b/test/fixedbugs/issue48357.go new file mode 100644 index 0000000000..5b39fc43d4 --- /dev/null +++ b/test/fixedbugs/issue48357.go @@ -0,0 +1,20 @@ +// run + +// Copyright 2021 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. + +package main + +import "reflect" + +type T [129]byte + +func main() { + m := map[string]T{} + v := reflect.ValueOf(m) + v.SetMapIndex(reflect.ValueOf("a"), reflect.ValueOf(T{})) + g = m["a"] +} + +var g T -- cgit v1.2.3-54-g00ecf