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master
test/fixedbugs/issue40629.go
69 строк
1 KB
Keith Randall
cmd/compile: fix live variable computation for deferreturn
15 авг 2020, 00:49
15 авг 2020, 00:49
32a84c9
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// run // Copyright 2020 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 "fmt" const N = 40 func main() { var x [N]int // stack-allocated memory for i := range x { x[i] = 0x999 } // This defer checks to see if x is uncorrupted. defer func(p *[N]int) { recover() for i := range p { if p[i] != 0x999 { for j := range p { fmt.Printf("p[%d]=0x%x\n", j, p[j]) } panic("corrupted stack variable") } } }(&x) // This defer starts a new goroutine, which will (hopefully) // overwrite x on the garbage stack. defer func() { c := make(chan bool) go func() { useStack(1000) c <- true }() <-c }() // This defer causes a stack copy. // The old stack is now garbage. defer func() { useStack(1000) }() // Trigger a segfault. *g = 0 // Make the return statement unreachable. // That makes the stack map at the deferreturn call empty. // In particular, the argument to the first defer is not // marked as a pointer, so it doesn't get adjusted // during the stack copy. for { } } var g *int64 func useStack(n int) { if n == 0 { return } useStack(n - 1) }