golang bug484 代码
文件路径：/test/fixedbugs/bug484.go
/ run
/ Copyright 2014 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 liveness code used to say that, in func g, s was live
/ starting at its declaration, because it appears to have its
/ address taken by the closure (different s, but the parser
/ gets slightly confused, a separate bug). The liveness analysis
/ saw s as having its address taken but the register optimizer
/ did not. This mismatch meant that s would be marked live
/ (and therefore initialized) at the call to f, but the register optimizer
/ would optimize away the initialization of s before f, causing the
/ garbage collector to use unused data.
/ The register optimizer has been changed to respect the
/ same "address taken" flag that the liveness analysis uses,
/ even if it cannot see any address being taken in the actual
/ machine code. This is conservative but keeps the two consistent,
/ which is the most important thing.
package main
import "runtime"
/go:noinline
func f() interface{} {
runtime.GC()
return nil
}
/go:noinline
func g() {
var s interface{}
_ = func() {
s := f()
_ = s
}
s = f()
useiface(s)
useiface(s)
}
/go:noinline
func useiface(x interface{}) {
}
/go:noinline
func h() {
var x [16]uintptr
for i := range x {
x[i] = 1
}
useint(x[0])
useint(x[1])
useint(x[2])
useint(x[3])
}
/go:noinline
func useint(x uintptr) {
}
func main() {
/ scribble non-zero values on stack
h()
/ call function that used to let the garbage collector
/ see uninitialized stack values; it will see the
/ nonzero values.
g()
}
func big(x int) {
if x >= 0 {
big(x - 1)
}
}