cmd/compile: rewrite a, b = f() to use temporaries when type not identical

If any of the LHS expressions of an OAS2FUNC are not identical to the
respective function call results, escape analysis mishandles the
implicit conversion, causes memory corruption.

Instead, we should insert autotmps like we already do for f(g()) calls
and return g() statements.

Fixes #46725

Change-Id: I71a08da0bf1a03d09a023da5b6f78fb37a4a4690
Reviewed-on: https://go-review.googlesource.com/c/go/+/327651
Trust: Cuong Manh Le <cuong.manhle.vn@gmail.com>
Run-TryBot: Cuong Manh Le <cuong.manhle.vn@gmail.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
This commit is contained in:
Cuong Manh Le 2021-06-13 22:28:44 +07:00
parent 3249b645c9
commit 326ea438bb
4 changed files with 73 additions and 3 deletions

View file

@ -204,8 +204,20 @@ assignOK:
r.Use = ir.CallUseList
rtyp := r.Type()
mismatched := false
failed := false
for i := range lhs {
assignType(i, rtyp.Field(i).Type)
result := rtyp.Field(i).Type
assignType(i, result)
if lhs[i].Type() == nil || result == nil {
failed = true
} else if lhs[i] != ir.BlankNode && !types.Identical(lhs[i].Type(), result) {
mismatched = true
}
}
if mismatched && !failed {
rewriteMultiValueCall(stmt, r)
}
return
}

View file

@ -989,6 +989,16 @@ func rewriteMultiValueCall(n ir.InitNode, call ir.Node) {
n.Args = list
case *ir.ReturnStmt:
n.Results = list
case *ir.AssignListStmt:
if n.Op() != ir.OAS2FUNC {
base.Fatalf("rewriteMultiValueCall: invalid op %v", n.Op())
}
as.SetOp(ir.OAS2FUNC)
n.SetOp(ir.OAS2)
n.Rhs = make([]ir.Node, len(list))
for i, tmp := range list {
n.Rhs[i] = AssignConv(tmp, n.Lhs[i].Type(), "assignment")
}
}
}

View file

@ -23,13 +23,13 @@ func main() {
{
// change of type for f
i, f, s := f3()
f, g, t := f3() // ERROR "redeclared|cannot assign|incompatible"
f, g, t := f3() // ERROR "redeclared|cannot assign|incompatible|cannot use"
_, _, _, _, _ = i, f, s, g, t
}
{
// change of type for i
i, f, s := f3()
j, i, t := f3() // ERROR "redeclared|cannot assign|incompatible"
j, i, t := f3() // ERROR "redeclared|cannot assign|incompatible|cannot use"
_, _, _, _, _ = i, f, s, j, t
}
{

View file

@ -0,0 +1,48 @@
// 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 "runtime"
type T [4]int
//go:noinline
func g(x []*T) ([]*T, []*T) { return x, x }
func main() {
const Jenny = 8675309
s := [10]*T{{Jenny}}
done := make(chan struct{})
runtime.SetFinalizer(s[0], func(p *T) { close(done) })
var h, _ interface{} = g(s[:])
if wait(done) {
panic("GC'd early")
}
if h.([]*T)[0][0] != Jenny {
panic("lost Jenny's number")
}
if !wait(done) {
panic("never GC'd")
}
}
func wait(done <-chan struct{}) bool {
for i := 0; i < 10; i++ {
runtime.GC()
select {
case <-done:
return true
default:
}
}
return false
}