github.com/mh-cbon/go@v0.0.0-20160603070303-9e112a3fe4c0/test/sizeof.go (about)

     1  // run
     2  
     3  // Copyright 2011 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  package main
     8  
     9  import "unsafe"
    10  
    11  type T struct {
    12  	X int
    13  }
    14  
    15  var t T
    16  
    17  func isUintptr(uintptr) {}
    18  
    19  type T2 struct {
    20  	A int32
    21  	U2
    22  }
    23  
    24  type U2 struct {
    25  	B int32
    26  	C int32
    27  }
    28  
    29  var t2 T2
    30  var p2 *T2
    31  
    32  func main() {
    33  	// Test unsafe.Sizeof, unsafe.Alignof, and unsafe.Offsetof all return uintptr.
    34  	isUintptr(unsafe.Sizeof(t))
    35  	isUintptr(unsafe.Alignof(t))
    36  	isUintptr(unsafe.Offsetof(t.X))
    37  
    38  	// Test correctness of Offsetof with respect to embedded fields (issue 4909).
    39  	if unsafe.Offsetof(t2.C) != 8 {
    40  		println(unsafe.Offsetof(t2.C), "!= 8")
    41  		panic("unsafe.Offsetof(t2.C) != 8")
    42  	}
    43  	if unsafe.Offsetof(p2.C) != 8 {
    44  		println(unsafe.Offsetof(p2.C), "!= 8")
    45  		panic("unsafe.Offsetof(p2.C) != 8")
    46  	}
    47  	if unsafe.Offsetof(t2.U2.C) != 4 {
    48  		println(unsafe.Offsetof(t2.U2.C), "!= 4")
    49  		panic("unsafe.Offsetof(t2.U2.C) != 4")
    50  	}
    51  	if unsafe.Offsetof(p2.U2.C) != 4 {
    52  		println(unsafe.Offsetof(p2.U2.C), "!= 4")
    53  		panic("unsafe.Offsetof(p2.U2.C) != 4")
    54  	}
    55  	testDeep()
    56  	testNotEmbedded()
    57  }
    58  
    59  type (
    60  	S1 struct {
    61  		A int64
    62  		S2
    63  	}
    64  	S2 struct {
    65  		B int64
    66  		S3
    67  	}
    68  	S3 struct {
    69  		C int64
    70  		S4
    71  	}
    72  	S4 struct {
    73  		D int64
    74  		S5
    75  	}
    76  	S5 struct {
    77  		E int64
    78  		S6
    79  	}
    80  	S6 struct {
    81  		F int64
    82  		S7
    83  	}
    84  	S7 struct {
    85  		G int64
    86  		S8
    87  	}
    88  	S8 struct {
    89  		H int64
    90  		*S1
    91  	}
    92  )
    93  
    94  func testDeep() {
    95  	var s1 S1
    96  	switch {
    97  	case unsafe.Offsetof(s1.A) != 0:
    98  		panic("unsafe.Offsetof(s1.A) != 0")
    99  	case unsafe.Offsetof(s1.B) != 8:
   100  		panic("unsafe.Offsetof(s1.B) != 8")
   101  	case unsafe.Offsetof(s1.C) != 16:
   102  		panic("unsafe.Offsetof(s1.C) != 16")
   103  	case unsafe.Offsetof(s1.D) != 24:
   104  		panic("unsafe.Offsetof(s1.D) != 24")
   105  	case unsafe.Offsetof(s1.E) != 32:
   106  		panic("unsafe.Offsetof(s1.E) != 32")
   107  	case unsafe.Offsetof(s1.F) != 40:
   108  		panic("unsafe.Offsetof(s1.F) != 40")
   109  	case unsafe.Offsetof(s1.G) != 48:
   110  		panic("unsafe.Offsetof(s1.G) != 48")
   111  	case unsafe.Offsetof(s1.H) != 56:
   112  		panic("unsafe.Offsetof(s1.H) != 56")
   113  	case unsafe.Offsetof(s1.S1) != 64:
   114  		panic("unsafe.Offsetof(s1.S1) != 64")
   115  	case unsafe.Offsetof(s1.S1.S2.S3.S4.S5.S6.S7.S8.S1.S2) != 8:
   116  		panic("unsafe.Offsetof(s1.S1.S2.S3.S4.S5.S6.S7.S8.S1.S2) != 8")
   117  	}
   118  }
   119  
   120  func testNotEmbedded() {
   121  	type T2 struct {
   122  		B int32
   123  		C int32
   124  	}
   125  	type T1 struct {
   126  		A int32
   127  		T2
   128  	}
   129  	type T struct {
   130  		Dummy int32
   131  		F     T1
   132  		P     *T1
   133  	}
   134  
   135  	var t T
   136  	var p *T
   137  	switch {
   138  	case unsafe.Offsetof(t.F.B) != 4:
   139  		panic("unsafe.Offsetof(t.F.B) != 4")
   140  	case unsafe.Offsetof(t.F.C) != 8:
   141  		panic("unsafe.Offsetof(t.F.C) != 8")
   142  
   143  	case unsafe.Offsetof(t.P.B) != 4:
   144  		panic("unsafe.Offsetof(t.P.B) != 4")
   145  	case unsafe.Offsetof(t.P.C) != 8:
   146  		panic("unsafe.Offsetof(t.P.C) != 8")
   147  
   148  	case unsafe.Offsetof(p.F.B) != 4:
   149  		panic("unsafe.Offsetof(p.F.B) != 4")
   150  	case unsafe.Offsetof(p.F.C) != 8:
   151  		panic("unsafe.Offsetof(p.F.C) != 8")
   152  
   153  	case unsafe.Offsetof(p.P.B) != 4:
   154  		panic("unsafe.Offsetof(p.P.B) != 4")
   155  	case unsafe.Offsetof(p.P.C) != 8:
   156  		panic("unsafe.Offsetof(p.P.C) != 8")
   157  	}
   158  }