Addedj changes suggestions proposed by JoeKar

link: #4052 (comment)
Signed-off-by: Nilton Perim Neto <niltonperimneto@gmail.com>

Author: niltonperimneto

internal/buffer/save.go

@@ -25,7 +25,6 @@ import (
 const LargeFileThreshold = 50000
 
 type wrappedFile struct {
-	name        string
 	writeCloser io.WriteCloser
 	withSudo    bool
 	screenb     bool
@@ -82,13 +81,13 @@ func openFile(name string, withSudo bool) (wrappedFile, error) {
 	var sigChan chan os.Signal
 
 	if withSudo {
-		conv := "notrunc"
+		args := []string{"dd", "bs=4k", "of=" + name}
 		// TODO: both platforms do not support dd with conv=fsync yet
 		if !(runtime.GOOS == "illumos" || runtime.GOOS == "netbsd") {
-			conv += ",fsync"
+			args = append(args, "conv=fsync")
 		}
 
-		cmd = exec.Command(config.GlobalSettings["sucmd"].(string), "dd", "bs=4k", "conv="+conv, "of="+name)
+		cmd = exec.Command(config.GlobalSettings["sucmd"].(string), args...)
 		writeCloser, err = cmd.StdinPipe()
 		if err != nil {
 			return wrappedFile{}, err
@@ -99,25 +98,10 @@ func openFile(name string, withSudo bool) (wrappedFile, error) {
 		signal.Notify(sigChan, os.Interrupt)
 
 		screenb = screen.TempFini()
-
-		// Truncate the file before starting the write process to ensure
-		// only one sudo process accesses the TTY at a time. Running both
-		// concurrently causes them to race on TCGETS2/TCSETS2 ioctls for
-		// the password prompt, deadlocking stdin routing.
-		truncCmd := exec.Command(config.GlobalSettings["sucmd"].(string), "dd", "count=0", "of="+name)
-		var truncStderr bytes.Buffer
-		truncCmd.Stderr = &truncStderr
-		if truncErr := truncCmd.Run(); truncErr != nil {
-			os.Stderr.Write(truncStderr.Bytes())
-			err = truncErr
-		} else {
-			// Need to start the process now, otherwise when we flush
-			// the file contents to its stdin it might hang because
-			// the kernel's pipe size is too small to handle the full
-			// file contents all at once.
-			err = cmd.Start()
-		}
-
+		// need to start the process now, otherwise when we flush the file
+		// contents to its stdin it might hang because the kernel's pipe size
+		// is too small to handle the full file contents all at once
+		err = cmd.Start()
 		if err != nil {
 			writeCloser.Close()
 			screen.TempStart(screenb)
@@ -132,15 +116,7 @@ func openFile(name string, withSudo bool) (wrappedFile, error) {
 		}
 	}
 
-	return wrappedFile{name, writeCloser, withSudo, screenb, cmd, sigChan}, nil
-}
-
-func (wf wrappedFile) Truncate() error {
-	if wf.withSudo {
-		// Nothing to do, truncation already done in openFile()
-		return nil
-	}
-	return wf.writeCloser.(*os.File).Truncate(0)
+	return wrappedFile{writeCloser, withSudo, screenb, cmd, sigChan}, nil
 }
 
 func (wf wrappedFile) Write(b *SharedBuffer) (int, error) {
@@ -161,9 +137,12 @@ func (wf wrappedFile) Write(b *SharedBuffer) (int, error) {
 		eol = []byte{'\n'}
 	}
 
-	err := wf.Truncate()
-	if err != nil {
-		return 0, err
+	if !wf.withSudo {
+		f := wf.writeCloser.(*os.File)
+		err := f.Truncate(0)
+		if err != nil {
+			return 0, err
+		}
 	}
 
 	// write lines
@@ -386,6 +365,9 @@ func (b *SharedBuffer) safeWrite(path string, withSudo bool, newFile bool) (int,
 
 	file, err := openFile(path, withSudo)
 	if err != nil {
+		if withSudo {
+			return 0, util.OverwriteError{What: err, BackupName: backupName}
+		}
 		return 0, err
 	}
 
@@ -407,12 +389,12 @@ func (b *SharedBuffer) safeWrite(path string, withSudo bool, newFile bool) (int,
 		size, err = file.Write(b)
 		if err != nil {
 			file.Close()
-			return 0, util.OverwriteError{err, backupName}
+			return 0, util.OverwriteError{What: err, BackupName: backupName}
 		}
 
 		err = file.Close()
 		if err != nil {
-			return 0, util.OverwriteError{err, backupName}
+			return 0, util.OverwriteError{What: err, BackupName: backupName}
 		}
 	}
 	b.forceKeepBackup = false