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Source file test/fixedbugs/issue17381.go

Documentation: test/fixedbugs

  // 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.
  
  // issue 17381: make sure leave function with non-empty frame
  // saves link register, so that traceback will work.
  
  package main
  
  import (
  	"runtime"
  	"unsafe"
  )
  
  func main() {
  	defer func() {
  		if recover() == nil {
  			panic("did not panic")
  		}
  		pcs := make([]uintptr, 20)
  		n := runtime.Callers(1, pcs)
  		for _, pc := range pcs[:n] {
  			if runtime.FuncForPC(pc).Name() == "main.main" {
  				return
  			}
  		}
  		panic("cannot find main.main in backtrace")
  	}()
  
  	prep()
  	f() // should panic
  }
  
  func funcPC(f interface{}) uintptr {
  	var ptr uintptr
  	return **(**uintptr)(unsafe.Pointer(uintptr(unsafe.Pointer(&f)) + unsafe.Sizeof(ptr)))
  }
  
  //go:noinline
  func f() {
  	var t [1]int // non-empty frame
  	*(*int)(nil) = t[0]
  }
  
  var p = funcPC(runtime.GC) + 8
  
  //go:noinline
  func prep() {
  	// put some garbage on stack
  	var x = [20]uintptr{p, p, p, p, p, p, p, p, p, p, p, p, p, p, p, p, p, p, p, p}
  	_ = x
  }
  

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