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Detect unnecessary imports instead of hardcoding
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@lu4p @mvdan
lu4p authored and mvdan committed Mar 25, 2022
1 parent 1a0b028 commit 237e0b7
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Showing 2 changed files with 126 additions and 162 deletions.
89 changes: 47 additions & 42 deletions main.go
View file
Original file line number Diff line number Diff line change
Expand Up @@ -748,6 +748,7 @@ func transformCompile(args []string) ([]string, error) {
if curPkg.ImportPath == "runtime" && flagTiny {
// strip unneeded runtime code
stripRuntime(filename, file)
tf.removeUnnecessaryImports(file)
}
tf.handleDirectives(file.Comments)
file = tf.transformGo(file)
Expand Down Expand Up @@ -1441,6 +1442,51 @@ func recordedAsNotObfuscated(obj types.Object) bool {
return ok
}

func (tf *transformer) removeUnnecessaryImports(file *ast.File) {
usedImports := make(map[string]bool)
ast.Inspect(file, func(n ast.Node) bool {
node, ok := n.(*ast.Ident)
if !ok {
return true
}

uses, ok := tf.info.Uses[node].(*types.PkgName)
if !ok {
return true
}

usedImports[uses.Imported().Path()] = true

return true
})

for _, imp := range file.Imports {
if imp.Name != nil && (imp.Name.Name == "_" || imp.Name.Name == ".") {
continue
}

path, err := strconv.Unquote(imp.Path.Value)
if err != nil {
panic(err)
}

// The import path can't be used directly here, because the actual
// path resolved via go/types might be different from the naive path.
lpkg, err := listPackage(path)
if err != nil {
panic(err)
}

if usedImports[lpkg.ImportPath] {
continue
}

if !astutil.DeleteImport(fset, file, path) {
panic(fmt.Sprintf("cannot delete unused import: %q", path))
}
}
}

// transformGo obfuscates the provided Go syntax file.
func (tf *transformer) transformGo(file *ast.File) *ast.File {
// Only obfuscate the literals here if the flag is on
Expand All @@ -1453,48 +1499,7 @@ func (tf *transformer) transformGo(file *ast.File) *ast.File {
file = literals.Obfuscate(file, tf.info, fset, tf.linkerVariableStrings)

// some imported constants might not be needed anymore, remove unnecessary imports
usedImports := make(map[string]bool)
ast.Inspect(file, func(n ast.Node) bool {
node, ok := n.(*ast.Ident)
if !ok {
return true
}

uses, ok := tf.info.Uses[node].(*types.PkgName)
if !ok {
return true
}

usedImports[uses.Imported().Path()] = true

return true
})

for _, imp := range file.Imports {
if imp.Name != nil && (imp.Name.Name == "_" || imp.Name.Name == ".") {
continue
}

path, err := strconv.Unquote(imp.Path.Value)
if err != nil {
panic(err)
}

// The import path can't be used directly here, because the actual
// path resolved via go/types might be different from the naive path.
lpkg, err := listPackage(path)
if err != nil {
panic(err)
}

if usedImports[lpkg.ImportPath] {
continue
}

if !astutil.DeleteImport(fset, file, path) {
panic(fmt.Sprintf("cannot delete unused import: %q", path))
}
}
tf.removeUnnecessaryImports(file)
}

pre := func(cursor *astutil.Cursor) bool {
Expand Down
199 changes: 79 additions & 120 deletions runtime_strip.go
View file
Original file line number Diff line number Diff line change
Expand Up @@ -5,7 +5,6 @@ package main

import (
"go/ast"
"go/token"
"strings"

ah "mvdan.cc/garble/internal/asthelper"
Expand Down Expand Up @@ -35,121 +34,93 @@ func stripRuntime(filename string, file *ast.File) {
}

for _, decl := range file.Decls {
switch x := decl.(type) {
case *ast.FuncDecl:
switch filename {
case "error.go":
// only used in panics
switch x.Name.Name {
case "printany", "printanycustomtype":
x.Body.List = nil
}
case "mgcscavenge.go":
// used in tracing the scavenger
if x.Name.Name == "printScavTrace" {
x.Body.List = nil
break
}
case "mprof.go":
// remove all functions that print debug/tracing info
// of the runtime
if strings.HasPrefix(x.Name.Name, "trace") {
x.Body.List = nil
}
case "panic.go":
// used for printing panics
switch x.Name.Name {
case "preprintpanics", "printpanics":
x.Body.List = nil
}
case "print.go":
// only used in tracebacks
if x.Name.Name == "hexdumpWords" {
x.Body.List = nil
break
}
case "proc.go":
// used in tracing the scheduler
if x.Name.Name == "schedtrace" {
x.Body.List = nil
break
}
case "runtime1.go":
usesEnv := func(node ast.Node) bool {
seen := false
ast.Inspect(node, func(node ast.Node) bool {
ident, ok := node.(*ast.Ident)
if ok && ident.Name == "gogetenv" {
seen = true
return false
}
return true
})
return seen
}
filenames:
switch x.Name.Name {
case "parsedebugvars":
// keep defaults for GODEBUG cgocheck and invalidptr,
// remove code that reads GODEBUG via gogetenv
for i, stmt := range x.Body.List {
if usesEnv(stmt) {
x.Body.List = x.Body.List[:i]
break filenames
}
funcDecl, ok := decl.(*ast.FuncDecl)
if !ok {
continue
}

switch filename {
case "error.go":
// only used in panics
switch funcDecl.Name.Name {
case "printany", "printanycustomtype":
funcDecl.Body.List = nil
}
case "mgcscavenge.go":
// used in tracing the scavenger
if funcDecl.Name.Name == "printScavTrace" {
funcDecl.Body.List = nil
}
case "mprof.go":
// remove all functions that print debug/tracing info
// of the runtime
if strings.HasPrefix(funcDecl.Name.Name, "trace") {
funcDecl.Body.List = nil
}
case "panic.go":
// used for printing panics
switch funcDecl.Name.Name {
case "preprintpanics", "printpanics":
funcDecl.Body.List = nil
}
case "print.go":
// only used in tracebacks
if funcDecl.Name.Name == "hexdumpWords" {
funcDecl.Body.List = nil
}
case "proc.go":
// used in tracing the scheduler
if funcDecl.Name.Name == "schedtrace" {
funcDecl.Body.List = nil
}
case "runtime1.go":
usesEnv := func(node ast.Node) bool {
seen := false
ast.Inspect(node, func(node ast.Node) bool {
ident, ok := node.(*ast.Ident)
if ok && ident.Name == "gogetenv" {
seen = true
return false
}
panic("did not see any gogetenv call in parsedebugvars")
case "setTraceback":
// tracebacks are completely hidden, no
// sense keeping this function
x.Body.List = nil
}
case "traceback.go":
// only used for printing tracebacks
switch x.Name.Name {
case "tracebackdefers", "printcreatedby", "printcreatedby1", "traceback", "tracebacktrap", "traceback1", "printAncestorTraceback",
"printAncestorTracebackFuncInfo", "goroutineheader", "tracebackothers", "tracebackHexdump", "printCgoTraceback":
x.Body.List = nil
case "printOneCgoTraceback":
x.Body = ah.BlockStmt(ah.ReturnStmt(ah.IntLit(0)))
default:
if strings.HasPrefix(x.Name.Name, "print") {
x.Body.List = nil
return true
})
return seen
}
filenames:
switch funcDecl.Name.Name {
case "parsedebugvars":
// keep defaults for GODEBUG cgocheck and invalidptr,
// remove code that reads GODEBUG via gogetenv
for i, stmt := range funcDecl.Body.List {
if usesEnv(stmt) {
funcDecl.Body.List = funcDecl.Body.List[:i]
break filenames
}
}
default:
break
}
case *ast.GenDecl:
if x.Tok != token.IMPORT {
continue
panic("did not see any gogetenv call in parsedebugvars")
case "setTraceback":
// tracebacks are completely hidden, no
// sense keeping this function
funcDecl.Body.List = nil
}

switch filename {
case "print.go":
// was used in hexdumpWords
x.Specs = removeImport(`"internal/goarch"`, x.Specs)
case "traceback.go":
// was used in traceback1
x.Specs = removeImport(`"runtime/internal/atomic"`, x.Specs)
case "traceback.go":
// only used for printing tracebacks
switch funcDecl.Name.Name {
case "tracebackdefers", "printcreatedby", "printcreatedby1", "traceback", "tracebacktrap", "traceback1", "printAncestorTraceback",
"printAncestorTracebackFuncInfo", "goroutineheader", "tracebackothers", "tracebackHexdump", "printCgoTraceback":
funcDecl.Body.List = nil
case "printOneCgoTraceback":
funcDecl.Body = ah.BlockStmt(ah.ReturnStmt(ah.IntLit(0)))
default:
if strings.HasPrefix(funcDecl.Name.Name, "print") {
funcDecl.Body.List = nil
}
}

}

}

switch filename {
case "runtime1.go":
// On Go 1.17.x, the code above results in runtime1.go having an
// unused import. Make it an underscore import.
// If this is a recurring problem, we could go for a more
// generic solution like x/tools/imports.
for _, imp := range file.Imports {
if imp.Path.Value == `"internal/bytealg"` {
imp.Name = &ast.Ident{Name: "_"}
break
}
}
case "print.go":
if filename == "print.go" {
file.Decls = append(file.Decls, hidePrintDecl)
return
}
Expand All @@ -160,18 +131,6 @@ func stripRuntime(filename string, file *ast.File) {
ast.Inspect(file, stripPrints)
}

func removeImport(importPath string, specs []ast.Spec) []ast.Spec {
for i, spec := range specs {
imp := spec.(*ast.ImportSpec)
if imp.Path.Value == importPath {
specs = append(specs[:i], specs[i+1:]...)
break
}
}

return specs
}

var hidePrintDecl = &ast.FuncDecl{
Name: ast.NewIdent("hidePrint"),
Type: &ast.FuncType{Params: &ast.FieldList{
Expand Down

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