1 // errorcheckoutput 2 3 package main 4 5 import "fmt" 6 7 // We are going to define 256 types T(n), 8 // such that T(n) embeds T(2n) and *T(2n+1). 9 10 func main() { 11 fmt.Printf("// errorcheck\n\n") 12 fmt.Printf("package p\n\n") 13 fmt.Println(`import "unsafe"`) 14 15 // Dump types. 16 for n := 1; n < 256; n++ { 17 writeStruct(n) 18 } 19 // Dump leaves 20 for n := 256; n < 512; n++ { 21 fmt.Printf("type T%d int\n", n) 22 } 23 24 fmt.Printf("var t T1\n") 25 fmt.Printf("var p *T1\n") 26 27 // Simple selectors 28 for n := 2; n < 256; n++ { 29 writeDot(n) 30 } 31 32 // Double selectors 33 for n := 128; n < 256; n++ { 34 writeDot(n/16, n) 35 } 36 37 // Triple selectors 38 for n := 128; n < 256; n++ { 39 writeDot(n/64, n/8, n) 40 } 41 } 42 43 const structTpl = ` 44 type T%d struct { 45 A%d int 46 T%d 47 *T%d 48 } 49 ` 50 51 func writeStruct(n int) { 52 fmt.Printf(structTpl, n, n, 2*n, 2*n+1) 53 } 54 55 func writeDot(ns ...int) { 56 for _, root := range []string{"t", "p"} { 57 fmt.Printf("const _ = unsafe.Offsetof(%s", root) 58 for _, n := range ns { 59 fmt.Printf(".T%d", n) 60 } 61 // Does it involve an indirection? 62 nlast := ns[len(ns)-1] 63 nprev := 1 64 if len(ns) > 1 { 65 nprev = ns[len(ns)-2] 66 } 67 isIndirect := false 68 for n := nlast / 2; n > nprev; n /= 2 { 69 if n%2 == 1 { 70 isIndirect = true 71 break 72 } 73 } 74 fmt.Print(")") 75 if isIndirect { 76 fmt.Print(` // ERROR "indirection"`) 77 } 78 fmt.Print("\n") 79 } 80 } 81
