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// 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)
}
}
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