printer: add generated code warnings

build/cli.go

@@ -58,7 +58,7 @@ func NewFlags(fs *flag.FlagSet) *Flags {
 }
 
 func (f *Flags) Config() *Config {
-	pc := printer.NewDefaultConfig()
+	pc := printer.NewGoRunConfig()
 	passes := []pass.Interface{pass.Compile}
 	for _, pv := range f.printers {
 		p := pv.Build(pc)

examples/add/add.s

@@ -1,3 +1,4 @@
+// Code generated by command: go run asm.go -out add.s -stubs stub.go. DO NOT EDIT.
 
 #include "textflag.h"
 

examples/complex/complex.s

@@ -1,3 +1,4 @@
+// Code generated by command: go run asm.go -out complex.s -stubs stub.go. DO NOT EDIT.
 
 #include "textflag.h"
 

examples/components/components.s

@@ -1,3 +1,4 @@
+// Code generated by command: go run asm.go -out components.s -stubs stub.go. DO NOT EDIT.
 
 #include "textflag.h"
 

examples/fnv1a/fnv1a.s

@@ -1,3 +1,4 @@
+// Code generated by command: go run asm.go -out fnv1a.s -stubs stub.go. DO NOT EDIT.
 
 #include "textflag.h"
 

examples/sum/sum.s

@@ -1,3 +1,4 @@
+// Code generated by command: go run asm.go -out sum.s -stubs stub.go. DO NOT EDIT.
 
 #include "textflag.h"
 

internal/cmd/avogen/main.go

@@ -46,7 +46,7 @@ func main() {
 		log.Fatalf("unknown generator type '%s'", t)
 	}
 
-	g := builder(printer.NewDefaultConfig())
+	g := builder(printer.NewArgvConfig())
 
 	// Determine output writer.
 	w := os.Stdout

internal/inst/table_test.go

@@ -71,7 +71,7 @@ func TestInstructionProperties(t *testing.T) {
 }
 
 func TestAssembles(t *testing.T) {
-	g := gen.NewAsmTest(printer.NewDefaultConfig())
+	g := gen.NewAsmTest(printer.NewArgvConfig())
 	b, err := g.Generate(inst.Instructions)
 	if err != nil {
 		t.Fatal(err)

internal/load/load_test.go

@@ -22,7 +22,7 @@ func Load(t *testing.T) []inst.Instruction {
 
 func TestAssembles(t *testing.T) {
 	is := Load(t)
-	g := gen.NewAsmTest(printer.NewDefaultConfig())
+	g := gen.NewAsmTest(printer.NewArgvConfig())
 	b, err := g.Generate(is)
 	if err != nil {
 		t.Fatal(err)

printer/goasm.go

@@ -29,6 +29,7 @@ func (p *goasm) Print(f *avo.File) ([]byte, error) {
 }
 
 func (p *goasm) header() {
+	p.Comment(p.cfg.GeneratedWarning())
 	p.NL()
 	p.include("textflag.h")
 }

printer/printer.go

@@ -4,6 +4,7 @@ import (
 	"fmt"
 	"os"
 	"path/filepath"
+	"runtime"
 	"strings"
 
 	"github.com/mmcloughlin/avo"
@@ -22,13 +23,34 @@ type Config struct {
 }
 
 func NewDefaultConfig() Config {
-	cfg := Config{
+	return Config{
+		Name: "avo",
+		Pkg:  pkg(),
+	}
+}
+
+func NewArgvConfig() Config {
+	return Config{
 		Argv: os.Args,
+		Pkg:  pkg(),
 	}
-	if cwd, err := os.Getwd(); err == nil {
-		cfg.Pkg = filepath.Base(cwd)
+}
+
+// NewGoRunConfig produces a Config for a generator that's expected to be
+// executed via "go run ...".
+func NewGoRunConfig() Config {
+	path := mainfile()
+	if path == "" {
+		return NewDefaultConfig()
+	}
+	argv := []string{"go", "run", filepath.Base(path)}
+	if len(os.Args) > 1 {
+		argv = append(argv, os.Args[1:]...)
+	}
+	return Config{
+		Argv: argv,
+		Pkg:  pkg(),
 	}
-	return cfg
 }
 
 func (c Config) GeneratedBy() string {
@@ -41,3 +63,33 @@ func (c Config) GeneratedBy() string {
 func (c Config) GeneratedWarning() string {
 	return fmt.Sprintf("Code generated by %s. DO NOT EDIT.", c.GeneratedBy())
 }
+
+// mainfile attempts to determine the file path of the main function by
+// inspecting the stack. Returns empty string on failure.
+func mainfile() string {
+	pc := make([]uintptr, 10)
+	n := runtime.Callers(0, pc)
+	if n == 0 {
+		return ""
+	}
+	pc = pc[:n]
+	frames := runtime.CallersFrames(pc)
+	for {
+		frame, more := frames.Next()
+		if frame.Function == "main.main" {
+			return frame.File
+		}
+		if !more {
+			break
+		}
+	}
+	return ""
+}
+
+// pkg guesses the name of the package from the working directory.
+func pkg() string {
+	if cwd, err := os.Getwd(); err == nil {
+		return filepath.Base(cwd)
+	}
+	return ""
+}

printer/stubs.go

@@ -15,8 +15,11 @@ func NewStubs(cfg Config) Printer {
 }
 
 func (s *stubs) Print(f *avo.File) ([]byte, error) {
-	s.Printf("package %s\n\n", s.cfg.Pkg)
+	s.Comment(s.cfg.GeneratedWarning())
+	s.NL()
+	s.Printf("package %s\n", s.cfg.Pkg)
 	for _, fn := range f.Functions {
+		s.NL()
 		s.Printf("%s\n", fn.Stub())
 	}
 	return s.Result()