all: use internal objcopy implementation

This lessens the dependency on binutils (e.g. arm-none-eabi-objcopy).

Gopkg.lock

@@ -1,6 +1,14 @@
 # This file is autogenerated, do not edit; changes may be undone by the next 'dep ensure'.
 
 
+[[projects]]
+  branch = "master"
+  digest = "1:00b45e06c7843541372fc17d982242bd6adfc2fc382b6f2e9ef9ce53d87a50b9"
+  name = "github.com/marcinbor85/gohex"
+  packages = ["."]
+  pruneopts = "UT"
+  revision = "7a43cd876e46e0f6ddc553f10f91731a78e6e949"
+
 [[projects]]
   branch = "master"
   digest = "1:ba70784a3deee74c0ca3c87bcac3c2f93d3b2d27d8f237b768c358b45ba47da8"
@@ -25,6 +33,7 @@
   analyzer-name = "dep"
   analyzer-version = 1
   input-imports = [
+    "github.com/marcinbor85/gohex",
     "golang.org/x/tools/go/ast/astutil",
     "golang.org/x/tools/go/ssa",
     "tinygo.org/x/go-llvm",

main.go

@@ -259,19 +259,12 @@ func Compile(pkgName, outpath string, spec *TargetSpec, config *BuildConfig, act
 			}
 		}
 
-		if outext == ".hex" || outext == ".bin" {
 		// Get an Intel .hex file or .bin file from the .elf file.
+		if outext == ".hex" || outext == ".bin" {
 			tmppath = filepath.Join(dir, "main"+outext)
-			format := map[string]string{
+			err := Objcopy(executable, tmppath)
-				".hex": "ihex",
-				".bin": "binary",
-			}[outext]
-			cmd := exec.Command(spec.Objcopy, "-O", format, executable, tmppath)
-			cmd.Stdout = os.Stdout
-			cmd.Stderr = os.Stderr
-			err = cmd.Run()
 			if err != nil {
-				return &commandError{"failed to extract " + format + " from", executable, err}
+				return err
 			}
 		}
 		return action(tmppath)

objcopy.go

@@ -0,0 +1,78 @@
+package main
+
+import (
+	"debug/elf"
+	"os"
+	"path/filepath"
+
+	"github.com/marcinbor85/gohex"
+)
+
+// ObjcopyError is an error returned by functions that act like objcopy.
+type ObjcopyError struct {
+	Op  string
+	Err error
+}
+
+func (e ObjcopyError) Error() string {
+	if e.Err == nil {
+		return e.Op
+	}
+	return e.Op + ": " + e.Err.Error()
+}
+
+// ExtractTextSegment returns the .text segment and the first address from the
+// ELF file in the given path.
+func ExtractTextSegment(path string) (uint64, []byte, error) {
+	f, err := elf.Open(path)
+	if err != nil {
+		return 0, nil, ObjcopyError{"failed to open ELF file to extract text segment", err}
+	}
+	defer f.Close()
+
+	text := f.Section(".text")
+	if text == nil {
+		return 0, nil, ObjcopyError{"file does not contain .text segment: " + path, nil}
+	}
+	data, err := text.Data()
+	if err != nil {
+		return 0, nil, ObjcopyError{"failed to extract .text segment from ELF file", err}
+	}
+	return text.Addr, data, nil
+}
+
+// Objcopy converts an ELF file to a different (simpler) output file format:
+// .bin or .hex. It extracts only the .text section.
+func Objcopy(infile, outfile string) error {
+	f, err := os.OpenFile(outfile, os.O_RDWR|os.O_CREATE|os.O_TRUNC, 0666)
+	if err != nil {
+		return err
+	}
+	defer f.Close()
+
+	// Read the .text segment.
+	addr, data, err := ExtractTextSegment(infile)
+	if err != nil {
+		return err
+	}
+
+	// Write to the file, in the correct format.
+	switch filepath.Ext(outfile) {
+	case ".bin":
+		// The address is not stored in a .bin file (therefore you
+		// should use .hex files in most cases).
+		_, err := f.Write(data)
+		return err
+	case ".hex":
+		mem := gohex.NewMemory()
+		mem.SetStartAddress(uint32(addr)) // ignored in most cases (Intel-specific)
+		err := mem.AddBinary(uint32(addr), data)
+		if err != nil {
+			return ObjcopyError{"failed to create .hex file", err}
+		}
+		mem.DumpIntelHex(f, 32) // TODO: handle error
+		return nil
+	default:
+		panic("unreachable")
+	}
+}

target.go

@@ -31,7 +31,6 @@ type TargetSpec struct {
 	CFlags     []string `json:"cflags"`
 	LDFlags    []string `json:"ldflags"`
 	ExtraFiles []string `json:"extra-files"`
-	Objcopy    string   `json:"objcopy"`
 	Emulator   []string `json:"emulator"`
 	Flasher    string   `json:"flash"`
 	OCDDaemon  []string `json:"ocd-daemon"`
@@ -72,9 +71,6 @@ func (spec *TargetSpec) copyProperties(spec2 *TargetSpec) {
 	spec.CFlags = append(spec.CFlags, spec2.CFlags...)
 	spec.LDFlags = append(spec.LDFlags, spec2.LDFlags...)
 	spec.ExtraFiles = append(spec.ExtraFiles, spec2.ExtraFiles...)
-	if spec2.Objcopy != "" {
-		spec.Objcopy = spec2.Objcopy
-	}
 	if len(spec2.Emulator) != 0 {
 		spec.Emulator = spec2.Emulator
 	}
@@ -217,7 +213,6 @@ func defaultTarget(goos, goarch, triple string) (*TargetSpec, error) {
 		BuildTags: []string{goos, goarch},
 		Compiler:  commands["clang"],
 		Linker:    "cc",
-		Objcopy:   "objcopy",
 		GDB:       "gdb",
 		GDBCmds:   []string{"run"},
 	}
@@ -230,13 +225,11 @@ func defaultTarget(goos, goarch, triple string) (*TargetSpec, error) {
 		// Some educated guesses as to how to invoke helper programs.
 		if goarch == "arm" && goos == "linux" {
 			spec.Linker = "arm-linux-gnueabihf-gcc"
-			spec.Objcopy = "arm-linux-gnueabihf-objcopy"
 			spec.GDB = "arm-linux-gnueabihf-gdb"
 			spec.Emulator = []string{"qemu-arm", "-L", "/usr/arm-linux-gnueabihf"}
 		}
 		if goarch == "arm64" && goos == "linux" {
 			spec.Linker = "aarch64-linux-gnu-gcc"
-			spec.Objcopy = "aarch64-linux-gnu-objcopy"
 			spec.GDB = "aarch64-linux-gnu-gdb"
 			spec.Emulator = []string{"qemu-aarch64", "-L", "/usr/aarch64-linux-gnu"}
 		}

targets/avr.json

@@ -4,7 +4,6 @@
 	"goarch": "wasm",
 	"compiler": "avr-gcc",
 	"linker": "avr-gcc",
-	"objcopy": "avr-objcopy",
 	"ldflags": [
 		"-T", "targets/avr.ld",
 		"-Wl,--gc-sections"

targets/cortex-m.json

@@ -16,6 +16,5 @@
 	"ldflags": [
 		"--gc-sections"
 	],
-	"objcopy": "arm-none-eabi-objcopy",
 	"gdb": "arm-none-eabi-gdb"
 }