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cmd/link: treat reflect.Value.Method like Call

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Fixes #14740

Change-Id: Iad8d971c21977b0a1f4ef55a08bb180a8125e976
Reviewed-on: https://go-review.googlesource.com/20562
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: David Crawshaw <crawshaw@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
This commit is contained in:
David Crawshaw 2016-03-10 19:32:04 -05:00
parent 5aa5db7593
commit e2836935bb
2 changed files with 47 additions and 13 deletions
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30
src/cmd/link/internal/ld/deadcode.go
View file

@ -25,7 +25,7 @@ import (
//
// 1. direct call
// 2. through a reachable interface type
// 3. reflect.Value.Call / reflect.Method.Func
// 3. reflect.Value.Call, .Method, or reflect.Method.Func
//
// The first case is handled by the flood fill, a directly called method
// is marked as reachable.
@ -35,11 +35,12 @@ import (
// against the interface method signatures, if it matches it is marked
// as reachable. This is extremely conservative, but easy and correct.
//
// The third case is handled by looking to see if reflect.Value.Call is
// ever marked reachable, or if a reflect.Method struct is ever
// constructed by a call to reflect.Type.Method or MethodByName. If it
// is, all bets are off and all exported methods of reachable types are
// marked reachable.
// The third case is handled by looking to see if any of:
// - reflect.Value.Call is reachable
// - reflect.Value.Method is reachable
// - reflect.Type.Method or MethodByName is called.
// If any of these happen, all bets are off and all exported methods
// of reachable types are marked reachable.
//
// Any unreached text symbols are removed from ctxt.Textp.
func deadcode(ctxt *Link) {
@ -58,14 +59,17 @@ func deadcode(ctxt *Link) {
d.flood()
callSym := Linkrlookup(ctxt, "reflect.Value.Call", 0)
callSymSeen := false
methSym := Linkrlookup(ctxt, "reflect.Value.Method", 0)
reflectSeen := false
for {
if callSym != nil && (callSym.Attr.Reachable() || d.reflectMethod) {
// Methods are called via reflection. Give up on
// static analysis, mark all exported methods of
// all reachable types as reachable.
callSymSeen = true
if !reflectSeen {
if d.reflectMethod || (callSym != nil && callSym.Attr.Reachable()) || (methSym != nil && methSym.Attr.Reachable()) {
// Methods might be called via reflection. Give up on
// static analysis, mark all exported methods of
// all reachable types as reachable.
reflectSeen = true
}
}
// Mark all methods that could satisfy a discovered
@ -74,7 +78,7 @@ func deadcode(ctxt *Link) {
// in the last pass.
var rem []methodref
for _, m := range d.markableMethods {
if (callSymSeen && m.isExported()) || d.ifaceMethod[m.m] {
if (reflectSeen && m.isExported()) || d.ifaceMethod[m.m] {
d.markMethod(m)
} else {
rem = append(rem, m)

30
test/reflectmethod4.go Normal file
View file

@ -0,0 +1,30 @@
// run
// Copyright 2016 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.
// The linker can prune methods that are not directly called or
// assigned to interfaces, but only if reflect.Value.Method is
// never used. Test it here.
package main
import "reflect"
var called = false
type M int
func (m M) UniqueMethodName() {
called = true
}
var v M
func main() {
reflect.ValueOf(v).Method(0).Interface().(func())()
if !called {
panic("UniqueMethodName not called")
}
}