diff options
| -rw-r--r-- | src/reflect/value.go | 8 | ||||
| -rw-r--r-- | src/runtime/stack.go | 1 | ||||
| -rw-r--r-- | test/fixedbugs/issue39541.go | 33 |
3 files changed, 42 insertions, 0 deletions
diff --git a/src/reflect/value.go b/src/reflect/value.go index 9ea95bc1d9..6daeb65b0f 100644 --- a/src/reflect/value.go +++ b/src/reflect/value.go @@ -577,6 +577,13 @@ func callReflect(ctxt *makeFuncImpl, frame unsafe.Pointer, retValid *bool) { // Convert v to type typ if v is assignable to a variable // of type t in the language spec. // See issue 28761. + if typ.Kind() == Interface { + // We must clear the destination before calling assignTo, + // in case assignTo writes (with memory barriers) to the + // target location used as scratch space. See issue 39541. + *(*uintptr)(addr) = 0 + *(*uintptr)(add(addr, ptrSize, "typ.size == 2*ptrSize")) = 0 + } v = v.assignTo("reflect.MakeFunc", typ, addr) // We are writing to stack. No write barrier. @@ -2367,6 +2374,7 @@ func NewAt(typ Type, p unsafe.Pointer) Value { // assignTo returns a value v that can be assigned directly to typ. // It panics if v is not assignable to typ. // For a conversion to an interface type, target is a suggested scratch space to use. +// target must be initialized memory (or nil). func (v Value) assignTo(context string, dst *rtype, target unsafe.Pointer) Value { if v.flag&flagMethod != 0 { v = makeMethodValue(context, v) diff --git a/src/runtime/stack.go b/src/runtime/stack.go index 7ae3eeef83..39876e2cc7 100644 --- a/src/runtime/stack.go +++ b/src/runtime/stack.go @@ -543,6 +543,7 @@ func adjustpointer(adjinfo *adjustinfo, vpp unsafe.Pointer) { } // Information from the compiler about the layout of stack frames. +// Note: this type must agree with reflect.bitVector. type bitvector struct { n int32 // # of bits bytedata *uint8 diff --git a/test/fixedbugs/issue39541.go b/test/fixedbugs/issue39541.go new file mode 100644 index 0000000000..fba52916eb --- /dev/null +++ b/test/fixedbugs/issue39541.go @@ -0,0 +1,33 @@ +// run + +// Copyright 2020 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" + +func sub(args []reflect.Value) []reflect.Value { + type A struct { + s int + t int + } + return []reflect.Value{reflect.ValueOf(A{1, 2})} +} + +func main() { + f := reflect.MakeFunc(reflect.TypeOf((func() interface{})(nil)), sub).Interface().(func() interface{}) + c := make(chan bool, 100) + for i := 0; i < 100; i++ { + go func() { + for j := 0; j < 10000; j++ { + f() + } + c <- true + }() + } + for i := 0; i < 100; i++ { + <-c + } +} |