mirror of
https://github.com/golang/go
synced 2024-11-14 13:20:30 -07:00
c65647d620
Previously statements like
f(unsafe.Pointer(g()), int(h()))
would be reordered into a sequence of statements like
autotmp_g := g()
autotmp_h := h()
f(unsafe.Pointer(autotmp_g), int(autotmp_h))
which can leave g's temporary value on the stack as a uintptr, rather
than an unsafe.Pointer. Instead, recognize uintptr-to-unsafe.Pointer
conversions when reordering function calls to instead produce:
autotmp_g := unsafe.Pointer(g())
autotmp_h := h()
f(autotmp_g, int(autotmp_h))
Fixes #15329.
Change-Id: I2cdbd89d233d0d5c94791513a9fd5fd958d11ed5
Reviewed-on: https://go-review.googlesource.com/22273
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>
Reviewed-by: Russ Cox <rsc@golang.org>
80 lines
2.1 KiB
Go
80 lines
2.1 KiB
Go
// 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.
|
|
|
|
// Previously, cmd/compile would rewrite
|
|
//
|
|
// check(unsafe.Pointer(testMeth(1).Pointer()), unsafe.Pointer(testMeth(2).Pointer()))
|
|
//
|
|
// to
|
|
//
|
|
// var autotmp_1 uintptr = testMeth(1).Pointer()
|
|
// var autotmp_2 uintptr = testMeth(2).Pointer()
|
|
// check(unsafe.Pointer(autotmp_1), unsafe.Pointer(autotmp_2))
|
|
//
|
|
// However, that means autotmp_1 is the only reference to the int
|
|
// variable containing the value "1", but it's not a pointer type,
|
|
// so it was at risk of being garbage collected by the evaluation of
|
|
// testMeth(2).Pointer(), even though package unsafe's documentation
|
|
// says the original code was allowed.
|
|
//
|
|
// Now cmd/compile rewrites it to
|
|
//
|
|
// var autotmp_1 unsafe.Pointer = unsafe.Pointer(testMeth(1).Pointer())
|
|
// var autotmp_2 unsafe.Pointer = unsafe.Pointer(testMeth(2).Pointer())
|
|
// check(autotmp_1, autotmp_2)
|
|
//
|
|
// to ensure the pointed-to variables are visible to the GC.
|
|
|
|
package main
|
|
|
|
import (
|
|
"fmt"
|
|
"reflect"
|
|
"runtime"
|
|
"unsafe"
|
|
)
|
|
|
|
func main() {
|
|
// Test all the different ways we can invoke reflect.Value.Pointer.
|
|
|
|
// Direct method invocation.
|
|
check(unsafe.Pointer(testMeth(1).Pointer()), unsafe.Pointer(testMeth(2).Pointer()))
|
|
|
|
// Invocation via method expression.
|
|
check(unsafe.Pointer(reflect.Value.Pointer(testMeth(1))), unsafe.Pointer(reflect.Value.Pointer(testMeth(2))))
|
|
|
|
// Invocation via interface.
|
|
check(unsafe.Pointer(testInter(1).Pointer()), unsafe.Pointer(testInter(2).Pointer()))
|
|
|
|
// Invocation via method value.
|
|
check(unsafe.Pointer(testFunc(1)()), unsafe.Pointer(testFunc(2)()))
|
|
}
|
|
|
|
func check(p, q unsafe.Pointer) {
|
|
a, b := *(*int)(p), *(*int)(q)
|
|
if a != 1 || b != 2 {
|
|
fmt.Printf("got %v, %v; expected 1, 2\n", a, b)
|
|
}
|
|
}
|
|
|
|
func testMeth(x int) reflect.Value {
|
|
// Force GC to run.
|
|
runtime.GC()
|
|
return reflect.ValueOf(&x)
|
|
}
|
|
|
|
type Pointerer interface {
|
|
Pointer() uintptr
|
|
}
|
|
|
|
func testInter(x int) Pointerer {
|
|
return testMeth(x)
|
|
}
|
|
|
|
func testFunc(x int) func() uintptr {
|
|
return testMeth(x).Pointer
|
|
}
|