Source file test/notinheap3.go

Documentation: test

     1  // errorcheck -+ -0 -l -d=wb
     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  // Test write barrier elimination for notinheap.
     8  
     9  package p
    10  
    11  type t1 struct {
    12  	x *nih
    13  	s []nih
    14  	y [1024]byte // Prevent write decomposition
    15  }
    16  
    17  type t2 struct {
    18  	x *ih
    19  	s []ih
    20  	y [1024]byte
    21  }
    22  
    23  //go:notinheap
    24  type nih struct {
    25  	x uintptr
    26  }
    27  
    28  type ih struct { // In-heap type
    29  	x uintptr
    30  }
    31  
    32  var (
    33  	v1 t1
    34  	v2 t2
    35  
    36  	v1s []t1
    37  	v2s []t2
    38  )
    39  
    40  func f() {
    41  	// Test direct writes
    42  	v1.x = nil        // no barrier
    43  	v2.x = nil        // ERROR "write barrier"
    44  	v1.s = []nih(nil) // no barrier
    45  	v2.s = []ih(nil)  // ERROR "write barrier"
    46  }
    47  
    48  func g() {
    49  	// Test aggregate writes
    50  	v1 = t1{x: nil} // no barrier
    51  	v2 = t2{x: nil} // ERROR "write barrier"
    52  }
    53  
    54  func h() {
    55  	// Test copies and appends.
    56  	copy(v1s, v1s[1:])      // no barrier
    57  	copy(v2s, v2s[1:])      // ERROR "write barrier"
    58  	_ = append(v1s, v1s...) // no barrier
    59  	_ = append(v2s, v2s...) // ERROR "write barrier"
    60  }
    61  
    62  // Slice clearing
    63  
    64  var (
    65  	sliceIH  []*ih
    66  	sliceNIH []*nih
    67  )
    68  
    69  func sliceClear() {
    70  	for i := range sliceIH {
    71  		sliceIH[i] = nil // ERROR "write barrier"
    72  	}
    73  	for i := range sliceNIH {
    74  		sliceNIH[i] = nil // no barrier
    75  	}
    76  }
    77  

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