Static Code Analysis Using SSA

Presented at GopherCon 2015

Transcript

1. Static Code Analysis Using SSA
2. ‘go’ toolchain is great!
3. go build go test go fmt go get go vet go tool cover go tool pprof go -race
4. What’s the next step?
5. Code generation
6. go/ast go/doc go/parser go/printer go/scanner go/token
7. Over 1,000 packages import go/ast
8. The AST only shows the structure of code
9. Static Single Assignment Intermediate Representation
10. SSA IR
11. SSA IR shows how code flows
12. golang.org/x/tools/go/ssa
13. golang.org/x/tools/go/ssa Primary Author: Alan Donovan
15. Only 5 projects import golang.org/x/tools/go/ssa
16. github.com/DanielMorsing/stackcheck github.com/go-llvm/llgo github.com/motemen/go-typeswitch-gen github.com/stripe/safesql github.com/tardisgo/tardisgo
17. Intermediate Representation Go IR Machine Code
18. IR is high level
19. IR is portable
20. x := 1 y := 2 x = x + y Static Single Assignment
21. x := 1 y := 2 x = x + y Static Single Assignment
22. x1 := 1 y1 := 2 x2 = x1 + y1 Static Single Assignment
23. SSA makes analysis easier
24. Terminology
25. Program github.com/benbjohnson/foo github.com/benbjohnson/bar fmt os io
26. github.com/benbjohnson/foo type Bar type Baz func Bat() Package
27. func hello(name string) { if name == “” { fmt.Print(“name?”) name = readString() } fmt.Printf(“hello %s”, name) } Function
28. func hello(name string) { if name == “” { fmt.Print(“name?”) name = readString() } fmt.Printf(“hello %s”, name) } Basic Blocks
29. fmt.Print(“name?”) name = readString() Control Flow Graph (CFG) fmt.Printf(“hello %s”, name) false true if name == “”
30. func hello(name string) { if name == “” { fmt.Print(“name?”) name = readString() } fmt.Printf(“hello %s”, name) } Instructions
31. func hello(name string) { if name == “” { fmt.Print(“name?”) name = readString() } fmt.Printf(“hello %s”, name) } Values
32. SSA IR Primitives Alloc BinOp Builtin Call ChangeInterface ChangeType Const Convert DebugRef Defer Extract Field FieldAddr FreeVar Function Global Go If Index IndexAddr Jump Lookup MakeChan MakeClosure MakeInterface MakeMap MakeSlice MapUpdate NamedConst Next Panic Parameter Phi Range Return RunDefers Select Send Slice Store Type TypeAssert UnOp
33. What does it look like?
34. package main import ( "flag" "fmt" "os" ) func main() { // Parse CLI arguments. flag.Parse() if flag.NArg() == 0 { fmt.Println("usage: hello NAME") os.Exit(2) } // Extract name from args and say hello. name := flag.Arg(0) sayHello(name) } func sayHello(name string) { fmt.Printf("hello, %s!", name) }
35. package main import ( "flag" "fmt" "os" ) func main() { // Parse CLI arguments. flag.Parse() if flag.NArg() == 0 { fmt.Println("usage: hello NAME") os.Exit(2) } // Extract name from args and say hello. name := flag.Arg(0) sayHello(name) } func sayHello(name string) { fmt.Printf("hello, %s!", name) }
36. package main import ( "flag" "fmt" "os" ) func main() { // Parse CLI arguments. flag.Parse() if flag.NArg() == 0 { fmt.Println("usage: hello NAME") os.Exit(2) } // Extract name from args and say hello. name := flag.Arg(0) sayHello(name) } func sayHello(name string) { fmt.Printf("hello, %s!", name) }
37. package main import ( "flag" "fmt" "os" ) func main() { // Parse CLI arguments. flag.Parse() if flag.NArg() == 0 { fmt.Println("usage: hello NAME") os.Exit(2) } // Extract name from args and say hello. name := flag.Arg(0) sayHello(name) } func sayHello(name string) { fmt.Printf("hello, %s!", name) } true
38. package main import ( "flag" "fmt" "os" ) func main() { // Parse CLI arguments. flag.Parse() if flag.NArg() == 0 { fmt.Println("usage: hello NAME") os.Exit(2) } // Extract name from args and say hello. name := flag.Arg(0) sayHello(name) } func sayHello(name string) { fmt.Printf("hello, %s!", name) } false
39. package main import ( "flag" "fmt" "os" ) func main() { // Parse CLI arguments. flag.Parse() if flag.NArg() == 0 { fmt.Println("usage: hello NAME") os.Exit(2) } // Extract name from args and say hello. name := flag.Arg(0) sayHello(name) } func sayHello(name string) { fmt.Printf("hello, %s!", name) }
40. package main import ( "flag" "fmt" "os" ) func main() { // Parse CLI arguments. flag.Parse() if flag.NArg() == 0 { fmt.Println("usage: hello NAME") os.Exit(2) } // Extract name from args and say hello. name := flag.Arg(0) sayHello(name) } func sayHello(name string) { fmt.Printf("hello, %s!", name) }
41. package main import ( "flag" "fmt" "os" ) func main() { // Parse CLI arguments. flag.Parse() if flag.NArg() == 0 { fmt.Println("usage: hello NAME") os.Exit(2) } // Extract name from args and say hello. name := flag.Arg(0) sayHello(name) } func sayHello(name string) { fmt.Printf("hello, %s!", name) }
42. $ ssadump -build=CPF -importbin .
43. func main(): 0: entry P:0 S:2 t0 = flag.Parse() () t1 = flag.NArg() int t2 = t1 == 0:int bool if t2 goto 1 else 2 1: if.then P:1 S:1 t3 = new [1]interface{} (varargs) *[1]interface{} t4 = &t3[0:int] *interface{} t5 = make interface{} <- string ("usage: hello NAME":string) interface{} *t4 = t5 t6 = slice t3[:] []interface{} t7 = fmt.Println(t6...) (n int, err error) t8 = os.Exit(2:int) () jump 2 2: if.done P:2 S:0 t9 = flag.Arg(0:int) string t10 = sayHello(t9) () return
44. func main(): 0: entry P:0 S:2 t0 = flag.Parse() () t1 = flag.NArg() int t2 = t1 == 0:int bool if t2 goto 1 else 2 1: if.then P:1 S:1 t3 = new [1]interface{} (varargs) *[1]interface{} t4 = &t3[0:int] *interface{} t5 = make interface{} <- string ("usage: hello NAME":string) interface{} *t4 = t5 t6 = slice t3[:] []interface{} t7 = fmt.Println(t6...) (n int, err error) t8 = os.Exit(2:int) () jump 2 2: if.done P:2 S:0 t9 = flag.Arg(0:int) string t10 = sayHello(t9) () return
45. func main(): 0: entry P:0 S:2 t0 = flag.Parse() () t1 = flag.NArg() int t2 = t1 == 0:int bool if t2 goto 1 else 2 1: if.then P:1 S:1 t3 = new [1]interface{} (varargs) *[1]interface{} t4 = &t3[0:int] *interface{} t5 = make interface{} <- string ("usage: hello NAME":string) interface{} *t4 = t5 t6 = slice t3[:] []interface{} t7 = fmt.Println(t6...) (n int, err error) t8 = os.Exit(2:int) () jump 2 2: if.done P:2 S:0 t9 = flag.Arg(0:int) string t10 = sayHello(t9) () return
46. func main(): 0: entry P:0 S:2 t0 = flag.Parse() () t1 = flag.NArg() int t2 = t1 == 0:int bool if t2 goto 1 else 2 1: if.then P:1 S:1 t3 = new [1]interface{} (varargs) *[1]interface{} t4 = &t3[0:int] *interface{} t5 = make interface{} <- string ("usage: hello NAME":string) interface{} *t4 = t5 t6 = slice t3[:] []interface{} t7 = fmt.Println(t6...) (n int, err error) t8 = os.Exit(2:int) () jump 2 2: if.done P:2 S:0 t9 = flag.Arg(0:int) string t10 = sayHello(t9) () return
47. func main(): 0: entry P:0 S:2 t0 = flag.Parse() () t1 = flag.NArg() int t2 = t1 == 0:int bool if t2 goto 1 else 2 1: if.then P:1 S:1 t3 = new [1]interface{} (varargs) *[1]interface{} t4 = &t3[0:int] *interface{} t5 = make interface{} <- string ("usage: hello NAME":string) interface{} *t4 = t5 t6 = slice t3[:] []interface{} t7 = fmt.Println(t6...) (n int, err error) t8 = os.Exit(2:int) () jump 2 2: if.done P:2 S:0 t9 = flag.Arg(0:int) string t10 = sayHello(t9) () return
48. func main(): 0: entry P:0 S:2 t0 = flag.Parse() () t1 = flag.NArg() int t2 = t1 == 0:int bool if t2 goto 1 else 2 1: if.then P:1 S:1 t3 = new [1]interface{} (varargs) *[1]interface{} t4 = &t3[0:int] *interface{} t5 = make interface{} <- string ("usage: hello NAME":string) interface{} *t4 = t5 t6 = slice t3[:] []interface{} t7 = fmt.Println(t6...) (n int, err error) t8 = os.Exit(2:int) () jump 2 2: if.done P:2 S:0 t9 = flag.Arg(0:int) string t10 = sayHello(t9) () return
49. func main(): 0: entry P:0 S:2 t0 = flag.Parse() () t1 = flag.NArg() int t2 = t1 == 0:int bool if t2 goto 1 else 2 1: if.then P:1 S:1 t3 = new [1]interface{} (varargs) *[1]interface{} t4 = &t3[0:int] *interface{} t5 = make interface{} <- string ("usage: hello NAME":string) interface{} *t4 = t5 t6 = slice t3[:] []interface{} t7 = fmt.Println(t6...) (n int, err error) t8 = os.Exit(2:int) () jump 2 2: if.done P:2 S:0 t9 = flag.Arg(0:int) string t10 = sayHello(t9) () return
50. func main(): 0: entry P:0 S:2 t0 = flag.Parse() () t1 = flag.NArg() int t2 = t1 == 0:int bool if t2 goto 1 else 2 1: if.then P:1 S:1 t3 = new [1]interface{} (varargs) *[1]interface{} t4 = &t3[0:int] *interface{} t5 = make interface{} <- string ("usage: hello NAME":string) interface{} *t4 = t5 t6 = slice t3[:] []interface{} t7 = fmt.Println(t6...) (n int, err error) t8 = os.Exit(2:int) () jump 2 2: if.done P:2 S:0 t9 = flag.Arg(0:int) string t10 = sayHello(t9) () return
51. func main(): 0: entry P:0 S:2 t0 = flag.Parse() () t1 = flag.NArg() int t2 = t1 == 0:int bool if t2 goto 1 else 2 1: if.then P:1 S:1 t3 = new [1]interface{} (varargs) *[1]interface{} t4 = &t3[0:int] *interface{} t5 = make interface{} <- string ("usage: hello NAME":string) interface{} *t4 = t5 t6 = slice t3[:] []interface{} t7 = fmt.Println(t6...) (n int, err error) t8 = os.Exit(2:int) () jump 2 2: if.done P:2 S:0 t9 = flag.Arg(0:int) string t10 = sayHello(t9) () return
52. func main(): 0: entry P:0 S:2 t0 = flag.Parse() () t1 = flag.NArg() int t2 = t1 == 0:int bool if t2 goto 1 else 2 1: if.then P:1 S:1 t3 = new [1]interface{} (varargs) *[1]interface{} t4 = &t3[0:int] *interface{} t5 = make interface{} <- string ("usage: hello NAME":string) interface{} *t4 = t5 t6 = slice t3[:] []interface{} t7 = fmt.Println(t6...) (n int, err error) t8 = os.Exit(2:int) () jump 2 2: if.done P:2 S:0 t9 = flag.Arg(0:int) string t10 = sayHello(t9) () return
53. func main(): 0: entry P:0 S:2 t0 = flag.Parse() () t1 = flag.NArg() int t2 = t1 == 0:int bool if t2 goto 1 else 2 1: if.then P:1 S:1 t3 = new [1]interface{} (varargs) *[1]interface{} t4 = &t3[0:int] *interface{} t5 = make interface{} <- string ("usage: hello NAME":string) interface{} *t4 = t5 t6 = slice t3[:] []interface{} t7 = fmt.Println(t6...) (n int, err error) t8 = os.Exit(2:int) () jump 2 2: if.done P:2 S:0 t9 = flag.Arg(0:int) string t10 = sayHello(t9) () return true
54. func main(): 0: entry P:0 S:2 t0 = flag.Parse() () t1 = flag.NArg() int t2 = t1 == 0:int bool if t2 goto 1 else 2 1: if.then P:1 S:1 t3 = new [1]interface{} (varargs) *[1]interface{} t4 = &t3[0:int] *interface{} t5 = make interface{} <- string ("usage: hello NAME":string) interface{} *t4 = t5 t6 = slice t3[:] []interface{} t7 = fmt.Println(t6...) (n int, err error) t8 = os.Exit(2:int) () jump 2 2: if.done P:2 S:0 t9 = flag.Arg(0:int) string t10 = sayHello(t9) () return false
55. func main(): 0: entry P:0 S:2 t0 = flag.Parse() () t1 = flag.NArg() int t2 = t1 == 0:int bool if t2 goto 1 else 2 1: if.then P:1 S:1 t3 = new [1]interface{} (varargs) *[1]interface{} t4 = &t3[0:int] *interface{} t5 = make interface{} <- string ("usage: hello NAME":string) interface{} *t4 = t5 t6 = slice t3[:] []interface{} t7 = fmt.Println(t6...) (n int, err error) t8 = os.Exit(2:int) () jump 2 2: if.done P:2 S:0 t9 = flag.Arg(0:int) string t10 = sayHello(t9) () return
56. func main(): 0: entry P:0 S:2 t0 = flag.Parse() () t1 = flag.NArg() int t2 = t1 == 0:int bool if t2 goto 1 else 2 1: if.then P:1 S:1 t3 = new [1]interface{} (varargs) *[1]interface{} t4 = &t3[0:int] *interface{} t5 = make interface{} <- string ("usage: hello NAME":string) interface{} *t4 = t5 t6 = slice t3[:] []interface{} t7 = fmt.Println(t6...) (n int, err error) t8 = os.Exit(2:int) () jump 2 2: if.done P:2 S:0 t9 = flag.Arg(0:int) string t10 = sayHello(t9) () return
57. func main(): 0: entry P:0 S:2 t0 = flag.Parse() () t1 = flag.NArg() int t2 = t1 == 0:int bool if t2 goto 1 else 2 1: if.then P:1 S:1 t3 = new [1]interface{} (varargs) *[1]interface{} t4 = &t3[0:int] *interface{} t5 = make interface{} <- string ("usage: hello NAME":string) interface{} *t4 = t5 t6 = slice t3[:] []interface{} t7 = fmt.Println(t6...) (n int, err error) t8 = os.Exit(2:int) () jump 2 2: if.done P:2 S:0 t9 = flag.Arg(0:int) string t10 = sayHello(t9) () return
58. func main(): 0: entry P:0 S:2 t0 = flag.Parse() () t1 = flag.NArg() int t2 = t1 == 0:int bool if t2 goto 1 else 2 1: if.then P:1 S:1 t3 = new [1]interface{} (varargs) *[1]interface{} t4 = &t3[0:int] *interface{} t5 = make interface{} <- string ("usage: hello NAME":string) interface{} *t4 = t5 t6 = slice t3[:] []interface{} t7 = fmt.Println(t6...) (n int, err error) t8 = os.Exit(2:int) () jump 2 2: if.done P:2 S:0 t9 = flag.Arg(0:int) string t10 = sayHello(t9) () return
59. func main(): 0: entry P:0 S:2 t0 = flag.Parse() () t1 = flag.NArg() int t2 = t1 == 0:int bool if t2 goto 1 else 2 1: if.then P:1 S:1 t3 = new [1]interface{} (varargs) *[1]interface{} t4 = &t3[0:int] *interface{} t5 = make interface{} <- string ("usage: hello NAME":string) interface{} *t4 = t5 t6 = slice t3[:] []interface{} t7 = fmt.Println(t6...) (n int, err error) t8 = os.Exit(2:int) () jump 2 2: if.done P:2 S:0 t9 = flag.Arg(0:int) string t10 = sayHello(t9) () return
60. func main(): 0: entry P:0 S:2 t0 = flag.Parse() () t1 = flag.NArg() int t2 = t1 == 0:int bool if t2 goto 1 else 2 1: if.then P:1 S:1 t3 = new [1]interface{} (varargs) *[1]interface{} t4 = &t3[0:int] *interface{} t5 = make interface{} <- string ("usage: hello NAME":string) interface{} *t4 = t5 t6 = slice t3[:] []interface{} t7 = fmt.Println(t6...) (n int, err error) t8 = os.Exit(2:int) () jump 2 2: if.done P:2 S:0 t9 = flag.Arg(0:int) string t10 = sayHello(t9) () return
61. func main(): 0: entry P:0 S:2 t0 = flag.Parse() () t1 = flag.NArg() int t2 = t1 == 0:int bool if t2 goto 1 else 2 1: if.then P:1 S:1 t3 = new [1]interface{} (varargs) *[1]interface{} t4 = &t3[0:int] *interface{} t5 = make interface{} <- string ("usage: hello NAME":string) interface{} *t4 = t5 t6 = slice t3[:] []interface{} t7 = fmt.Println(t6...) (n int, err error) t8 = os.Exit(2:int) () jump 2 2: if.done P:2 S:0 t9 = flag.Arg(0:int) string t10 = sayHello(t9) () return
62. func main(): 0: entry P:0 S:2 t0 = flag.Parse() () t1 = flag.NArg() int t2 = t1 == 0:int bool if t2 goto 1 else 2 1: if.then P:1 S:1 t3 = new [1]interface{} (varargs) *[1]interface{} t4 = &t3[0:int] *interface{} t5 = make interface{} <- string ("usage: hello NAME":string) interface{} *t4 = t5 t6 = slice t3[:] []interface{} t7 = fmt.Println(t6...) (n int, err error) t8 = os.Exit(2:int) () jump 2 2: if.done P:2 S:0 t9 = flag.Arg(0:int) string t10 = sayHello(t9) () return ???
63. func main(): 0: entry P:0 S:2 t0 = flag.Parse() () t1 = flag.NArg() int t2 = t1 == 0:int bool if t2 goto 1 else 2 1: if.then P:1 S:1 t3 = new [1]interface{} (varargs) *[1]interface{} t4 = &t3[0:int] *interface{} t5 = make interface{} <- string ("usage: hello NAME":string) interface{} *t4 = t5 t6 = slice t3[:] []interface{} t7 = fmt.Println(t6...) (n int, err error) t8 = os.Exit(2:int) () jump 2 2: if.done P:2 S:0 t9 = flag.Arg(0:int) string t10 = sayHello(t9) () return
64. func main(): 0: entry P:0 S:2 t0 = flag.Parse() () t1 = flag.NArg() int t2 = t1 == 0:int bool if t2 goto 1 else 2 1: if.then P:1 S:1 t3 = new [1]interface{} (varargs) *[1]interface{} t4 = &t3[0:int] *interface{} t5 = make interface{} <- string ("usage: hello NAME":string) interface{} *t4 = t5 t6 = slice t3[:] []interface{} t7 = fmt.Println(t6...) (n int, err error) t8 = os.Exit(2:int) () jump 2 2: if.done P:2 S:0 t9 = flag.Arg(0:int) string t10 = sayHello(t9) () return
65. func main(): 0: entry P:0 S:2 t0 = flag.Parse() () t1 = flag.NArg() int t2 = t1 == 0:int bool if t2 goto 1 else 2 1: if.then P:1 S:1 t3 = new [1]interface{} (varargs) *[1]interface{} t4 = &t3[0:int] *interface{} t5 = make interface{} <- string ("usage: hello NAME":string) interface{} *t4 = t5 t6 = slice t3[:] []interface{} t7 = fmt.Println(t6...) (n int, err error) t8 = os.Exit(2:int) () jump 2 2: if.done P:2 S:0 t9 = flag.Arg(0:int) string t10 = sayHello(t9) () return
66. func main(): 0: entry P:0 S:2 t0 = flag.Parse() () t1 = flag.NArg() int t2 = t1 == 0:int bool if t2 goto 1 else 2 1: if.then P:1 S:1 t3 = new [1]interface{} (varargs) *[1]interface{} t4 = &t3[0:int] *interface{} t5 = make interface{} <- string ("usage: hello NAME":string) interface{} *t4 = t5 t6 = slice t3[:] []interface{} t7 = fmt.Println(t6...) (n int, err error) t8 = os.Exit(2:int) () jump 2 2: if.done P:2 S:0 t9 = flag.Arg(0:int) string t10 = sayHello(t9) () return
67. func main(): 0: entry P:0 S:2 t0 = flag.Parse() () t1 = flag.NArg() int t2 = t1 == 0:int bool if t2 goto 1 else 2 1: if.then P:1 S:1 t3 = new [1]interface{} (varargs) *[1]interface{} t4 = &t3[0:int] *interface{} t5 = make interface{} <- string ("usage: hello NAME":string) interface{} *t4 = t5 t6 = slice t3[:] []interface{} t7 = fmt.Println(t6...) (n int, err error) t8 = os.Exit(2:int) () jump 2 2: if.done P:2 S:0 t9 = flag.Arg(0:int) string t10 = sayHello(t9) () return
68. Tools built on go/ssa
69. safesql
70. safesql • Written by Carl Jackson at Stripe. • Verifies that the query string arg is a compile time constant. • Helps to prevent SQL injection.
71. safesql func main() { // Open database. db, err := sql.Open("postgres", "dbname=db0") if err != nil { log.Fatal(err) } defer db.Close() // Retrieve color from CLI args. color := flag.Arg(0) // Execute query. db.Query("SELECT FROM widgets WHERE color = '" + color + "'") }
72. safesql func main() { // Open database. db, err := sql.Open("postgres", "dbname=db0") if err != nil { log.Fatal(err) } defer db.Close() // Retrieve color from CLI args. color := flag.Arg(0) // Execute query. db.Query("SELECT FROM widgets WHERE color = '" + color + "'") } User Input
73. safesql func main() { // Open database. db, err := sql.Open("postgres", "dbname=db0") if err != nil { log.Fatal(err) } defer db.Close() // Retrieve color from CLI args. color := flag.Arg(0) // Execute query. db.Query("SELECT FROM widgets WHERE color = '" + color + "'") } Ah! SQL Injection!
74. safesql $ safesql . Found 1 potentially unsafe SQL statements: - main.go:13:10 Please ensure that all SQL queries you use are compile-time constants. You should always use parameterized queries or prepared statements instead of building queries from strings.
75. safesql const FavColor = “purple” func main() { // Open database. db, err := sql.Open("postgres", "dbname=db0") if err != nil { log.Fatal(err) } defer db.Close() // Execute query. db.Query("SELECT FROM widgets WHERE color = '" + FavColor + "'") }
76. safesql $ safesql . You're safe from SQL injection! Yay \o/
77. oracle
78. oracle • Provides insights about your code. • Even works with interfaces! • Uses pointer analysis to scan your whole program
79. oracle • What code calls a function • What code is called by a function • Trace possible paths to a function call from main() • Determine what implements an interface • Find who sends to & receives from a channel • Determine possible values of a pointer • Find other identifiers that refer to the same value
80. oracle callees
81. type I interface { Foo() } type T struct{} func (*T) Foo() {} type V struct{} func (*V) Foo() {} func doSomething(condition bool) { var x I = &T{} x.Foo() if condition { x = &V{} } x.Foo() }
82. $ oracle -pos main.go:#168 callees main.go main.go:24:7: this dynamic method call dispatches to: main.go:7:11: (*main.T).Foo
83. type I interface { Foo() } type T struct{} func (*T) Foo() {} type V struct{} func (*V) Foo() {} func doSomething(condition bool) { var x I = &T{} x.Foo() if condition { x = &V{} } x.Foo() }
84. $ oracle -pos main.go:#210 callees main.go main.go:24:7: this dynamic method call dispatches to: main.go:7:11: (*main.T).Foo main.go:11:11: (*main.V).Foo
85. oracle callers
86. type I interface { Foo() } type T struct{} func (*T) Foo() {} type V struct{} func (*V) Foo() {} func doSomething(condition bool) { var x I = &T{} if condition { x = &V{} x.Foo() } }
87. type I interface { Foo() } type T struct{} func (*T) Foo() {} type V struct{} func (*V) Foo() {} func doSomething(condition bool) { var x I = &T{} if condition { x = &V{} x.Foo() } }
88. $ oracle -pos main.go:#61 callers main.go main.go:7:11: (*main.T).Foo is not reachable in this program.
89. type I interface { Foo() } type T struct{} func (*T) Foo() {} type V struct{} func (*V) Foo() {} func doSomething(condition bool) { var x I = &T{} if condition { x = &V{} x.Foo() } }
90. $ oracle -pos main.go:#98 callers main.go main.go:11:11: (*main.V).Foo is called from these 1 sites: main.go:22:8: dynamic method call from main.main
91. oracle pointsto
92. type T struct{} func (*T) Foo() {} type V struct{} func (*V) Foo() {} type I interface { Foo() } func doSomething(cond bool) { var x I = &T{} if cond { x = &V{} } fmt.Printf("x is %T\n", x) }
93. type T struct{} func (*T) Foo() {} type V struct{} func (*V) Foo() {} type I interface { Foo() } func doSomething(cond bool) { var x I = &T{} if cond { x = &V{} } fmt.Printf("x is %T\n", x) }
94. $ oracle -pos main.go:#168 pointsto main.go main.go:21:6: this I may contain these dynamic types: main.go:8:6: *T, may point to: main.go:21:14: complit
95. type T struct{} func (*T) Foo() {} type V struct{} func (*V) Foo() {} type I interface { Foo() } func doSomething(cond bool) { var x I = &T{} if cond { x = &V{} } fmt.Printf("x is %T\n", x) }
96. $ oracle -pos main.go:#206 pointsto main.go main.go:24:3: this I may contain these dynamic types: main.go:12:6: *V, may point to: main.go:24:9: complit
97. type T struct{} func (*T) Foo() {} type V struct{} func (*V) Foo() {} type I interface { Foo() } func doSomething(cond bool) { var x I = &T{} if cond { x = &V{} } fmt.Printf("x is %T\n", x) }
98. $ oracle -pos main.go:#244 pointsto main.go main.go:27:26: this I may contain these dynamic types: main.go:8:6: *T, may point to: main.go:21:14: complit main.go:12:6: *V, may point to: main.go:24:9: complit
99. gorename
100. gorename • Safely renames identifiers • Renames the declaration as well as references. • Even works across packages in GOPATH • Just uses go/types but it’s still cool • Intelligently prevents ambiguity and shadowing conflicts.
101. gorename func doSomething() { var x int if y := rand.Intn(10); y == 0 { x = 1 } fmt.Printf("x is %d\n", x) } Shadowing Conflict
102. gorename $ gorename -from mypkg.doSomething::x -to y Shadowing Conflict
103. gorename mypkg.go:2:6: renaming this var "x" to "y" mypkg.go:4:3: would cause this reference to become shadowed mypkg.go:5:5: by this intervening var definition Shadowing Conflict
104. gorename package mypkg type Widget struct { Name string } ... type Woojit struct { Widget Floojit string } Ambiguity Conflict
105. gorename $ gorename -from mypkg.Widget -to Floojit Ambiguity Conflict
106. gorename main.go:8:2: renaming this field "Widget" to "Floojit" main.go:9:2: would conflict with this field Ambiguity Conflict
107. golang.org/x/tools
108. It’s just the beginning! There is so much to build!
109. Q&A @benbjohnson