issue16515.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 16515: spilled Duff-adjusted address may be invalid
     8  
     9  package main
    10  
    11  import "runtime"
    12  
    13  type T [62]int // DUFFZERO with non-zero adjustment on AMD64
    14  
    15  var sink interface{}
    16  
    17  //go:noinline
    18  func zero(x *T) {
    19  	// Two DUFFZEROs on the same address with a function call in between.
    20  	// Duff-adjusted address will be spilled and loaded
    21  
    22  	*x = T{} // DUFFZERO
    23  	runtime.GC()
    24  	(*x)[0] = 1
    25  	g()      // call a function with large frame, trigger a stack move
    26  	*x = T{} // DUFFZERO again
    27  }
    28  
    29  //go:noinline
    30  // a function with large frame
    31  func g() {
    32  	var x [1000]int
    33  	_ = x
    34  }
    35  
    36  func main() {
    37  	var s struct { a T; b [8192-62]int } // allocate 64K, hopefully it's in a new span and a few bytes before it is garbage
    38  	sink = &s // force heap allocation
    39  	s.a[0] = 2
    40  	zero(&s.a)
    41  	if s.a[0] != 0 {
    42  		println("s.a[0] =", s.a[0])
    43  		panic("zeroing failed")
    44  	}
    45  
    46  	var a T // on stack
    47  	a[0] = 2
    48  	zero(&a)
    49  	if a[0] != 0 {
    50  		println("a[0] =", a[0])
    51  		panic("zeroing failed")
    52  	}
    53  }
    54
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