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master
test/fixedbugs/issue16249.go
58 строк
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Ian Lance Taylor
cmd/compile: mark live heap-allocated pparamout vars as needzero
02 июл 2016, 03:40
02 июл 2016, 03:40
519b469
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// 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. // Liveness calculations were wrong for a result parameter pushed onto // the heap in a function that used defer. Program would crash with // runtime: bad pointer in frame main.A at 0xc4201e6838: 0x1 package main import "errors" var sink interface{} //go:noinline func f(err *error) { if err != nil { sink = err } } //go:noinline func A(n, m int64) (res int64, err error) { defer f(&err) // output parameter's address escapes to a defer. if n < 0 { err = errors.New("No negative") return } if n <= 1 { res = n return } res = B(m) // This call to B drizzles a little junk on the stack. res, err = A(n-1, m) res++ return } // B does a little bit of recursion dribbling not-zero onto the stack. //go:noinline func B(n int64) (res int64) { if n <= 1 { // Prefer to leave a 1 on the stack. return n } return 1 + B(n-1) } func main() { x, e := A(0, 0) for j := 0; j < 4; j++ { // j controls amount of B's stack dribble for i := 0; i < 1000; i++ { // try more and more recursion until stack growth occurs in newobject in prologue x, e = A(int64(i), int64(j)) } } _, _ = x, e }