Unsafe defer of
.Close method GO-S2307Deferring unsafe method "Close" on type "io.WriteCloser"
36 if err != nil {
37 return 0, err
38 }
39 defer writer.Close()40 return writer.Write(p)
41}
42Deferring unsafe method "Close" on type "*os.File"
1270 if err != nil {
1271 errorExit("Unable to create temporary file")
1272 }
1273 defer f.Close()1274
1275 f.WriteString(strings.Join(data, printSep))
1276 f.WriteString(printSep)Deferring unsafe method "Close" on type "net.Conn"
23 }
24
25 go func() {
26 defer c.Close()27 // nop
28 }()
29 }
Description
Calling Close() method may return an error, and ignoring the same
might result in a data loss. This is similar to many more Close methods.
For example, on POSIX systems, os.Close uses the close system call underneath,
which may return an EIO:
A previously-uncommitted write(2) encountered an input/output error.
This means that the data written by os.Write hasn't been written to the disk,
which results in a data loss. It is recommended to handle the error returned
by the os.Close call or call os.Sync if available to force the OS to write
the data to the disk.
Bad practice
package main
import (
"fmt"
"os"
)
func foo() error {
f, err := os.Create("/tmp/test.txt")
if err != nil {
return err
}
defer f.Close()
return fmt.Fprint(f, "Hello World")
}
Recommended
package main
import (
"fmt"
"os"
)
func foo() error {
f, err := os.Create("/tmp/test.txt")
if err != nil {
return err
}
err = fmt.Fprint(f, "Hello World")
if err != nil {
return err
}
return f.Close()
}
package main
import (
"fmt"
"os"
)
func foo() error {
f, err := os.Create("/tmp/test.txt")
if err != nil {
return err
}
defer f.Close()
err = fmt.Fprint(f, "Hello World")
if err != nil {
return err
}
return f.Sync()
}