issue17381.go

     1  // run
     2  
     3  // Copyright 2016 The Go Authors. All rights reserved.
     4  // Use of this source code is governed by a BSD-style
     5  // license that can be found in the LICENSE file.
     6  
     7  // issue 17381: make sure leave function with non-empty frame
     8  // saves link register, so that traceback will work.
     9  
    10  package main
    11  
    12  import (
    13  	"runtime"
    14  	"unsafe"
    15  )
    16  
    17  func main() {
    18  	defer func() {
    19  		if recover() == nil {
    20  			panic("did not panic")
    21  		}
    22  		pcs := make([]uintptr, 20)
    23  		n := runtime.Callers(1, pcs)
    24  		for _, pc := range pcs[:n] {
    25  			if runtime.FuncForPC(pc).Name() == "main.main" {
    26  				return
    27  			}
    28  		}
    29  		panic("cannot find main.main in backtrace")
    30  	}()
    31  
    32  	prep()
    33  	f() // should panic
    34  }
    35  
    36  func funcPC(f interface{}) uintptr {
    37  	var ptr uintptr
    38  	return **(**uintptr)(unsafe.Pointer(uintptr(unsafe.Pointer(&f)) + unsafe.Sizeof(ptr)))
    39  }
    40  
    41  //go:noinline
    42  func f() {
    43  	var t [1]int // non-empty frame
    44  	*(*int)(nil) = t[0]
    45  }
    46  
    47  var p = funcPC(runtime.GC) + 8
    48  
    49  //go:noinline
    50  func prep() {
    51  	// put some garbage on stack
    52  	var x = [20]uintptr{p, p, p, p, p, p, p, p, p, p, p, p, p, p, p, p, p, p, p, p}
    53  	_ = x
    54  }
    55
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