gometalinter: clean up some errcheck warnings

Check some errors where relevant.
Unfortunately enabling errcheck does not look feasible, too many warnings.

Update #538

3 files changed, 32 insertions, 17 deletions

diff --git a/pkg/db/db.go b/pkg/db/db.go
index 4d48e1229..5c2755860 100644
--- a/pkg/db/db.go
+++ b/pkg/db/db.go
@@ -47,7 +47,9 @@ func Open(filename string) (*DB, error) {
 	db.Version, db.Records, db.uncompacted = deserializeDB(bufio.NewReader(f))
 	f.Close()
 	if len(db.Records) == 0 || db.uncompacted/10*9 > len(db.Records) {
-		db.compact()
+		if err := db.compact(); err != nil {
+			return nil, err
+		}
 	}
 	return db, nil
 }
@@ -75,8 +77,7 @@ func (db *DB) Delete(key string) {
 
 func (db *DB) Flush() error {
 	if db.uncompacted/10*9 > len(db.Records) {
-		db.compact()
-		return nil
+		return db.compact()
 	}
 	if db.pending == nil {
 		return nil
@@ -168,7 +169,6 @@ func serializeRecord(w *bytes.Buffer, key string, val []byte, seq uint64) {
 		if _, err := fw.Write(val); err != nil {
 			panic(err)
 		}
-		fw.Flush()
 		fw.Close()
 		binary.Write(bytes.NewBuffer(w.Bytes()[lenPos:lenPos:lenPos+8]), binary.LittleEndian, uint32(len(w.Bytes())-startPos))
 	}
diff --git a/pkg/host/host_linux.go b/pkg/host/host_linux.go
index 38b2461f1..6d7c9c516 100644
--- a/pkg/host/host_linux.go
+++ b/pkg/host/host_linux.go
@@ -337,8 +337,8 @@ func checkCoverage() string {
 	return ""
 }
 
-func checkComparisons() string {
-	if reason := checkDebugFS(); reason != "" {
+func checkComparisons() (reason string) {
+	if reason = checkDebugFS(); reason != "" {
 		return reason
 	}
 	// TODO(dvyukov): this should run under target arch.
@@ -365,7 +365,11 @@ func checkComparisons() string {
 	if err != nil {
 		return fmt.Sprintf("KCOV mmap failed: %v", err)
 	}
-	defer syscall.Munmap(mem)
+	defer func() {
+		if err := syscall.Munmap(mem); err != nil {
+			reason = fmt.Sprintf("munmap failed: %v", err)
+		}
+	}()
 	_, _, errno = syscall.Syscall(syscall.SYS_IOCTL,
 		uintptr(fd), linux.KCOV_ENABLE, linux.KCOV_TRACE_CMP)
 	if errno != 0 {
@@ -374,7 +378,12 @@ func checkComparisons() string {
 		}
 		return fmt.Sprintf("ioctl(KCOV_TRACE_CMP) failed: %v", errno)
 	}
-	defer syscall.Syscall(syscall.SYS_IOCTL, uintptr(fd), linux.KCOV_DISABLE, 0)
+	defer func() {
+		_, _, errno = syscall.Syscall(syscall.SYS_IOCTL, uintptr(fd), linux.KCOV_DISABLE, 0)
+		if errno != 0 {
+			reason = fmt.Sprintf("ioctl(KCOV_DISABLE) failed: %v", errno)
+		}
+	}()
 	return ""
 }
 
diff --git a/pkg/rpctype/rpc.go b/pkg/rpctype/rpc.go
index 3838855a4..417a4f7b8 100644
--- a/pkg/rpctype/rpc.go
+++ b/pkg/rpctype/rpc.go
@@ -26,7 +26,9 @@ func NewRPCServer(addr string, receiver interface{}) (*RPCServer, error) {
 		return nil, fmt.Errorf("failed to listen on %v: %v", addr, err)
 	}
 	s := rpc.NewServer()
-	s.Register(receiver)
+	if err := s.Register(receiver); err != nil {
+		return nil, err
+	}
 	serv := &RPCServer{
 		ln: ln,
 		s:  s,
@@ -41,8 +43,7 @@ func (serv *RPCServer) Serve() {
 			log.Logf(0, "failed to accept an rpc connection: %v", err)
 			continue
 		}
-		conn.(*net.TCPConn).SetKeepAlive(true)
-		conn.(*net.TCPConn).SetKeepAlivePeriod(10 * time.Second)
+		setupKeepAlive(conn, 10*time.Second)
 		go serv.s.ServeConn(newFlateConn(conn))
 	}
 }
@@ -66,8 +67,7 @@ func Dial(addr string) (net.Conn, error) {
 	if conn, err = net.DialTimeout("tcp", addr, 60*time.Second); err != nil {
 		return nil, err
 	}
-	conn.(*net.TCPConn).SetKeepAlive(true)
-	conn.(*net.TCPConn).SetKeepAlivePeriod(time.Minute)
+	setupKeepAlive(conn, time.Minute)
 	return conn, nil
 }
 
@@ -84,10 +84,11 @@ func NewRPCClient(addr string) (*RPCClient, error) {
 }
 
 func (cli *RPCClient) Call(method string, args, reply interface{}) error {
-	cli.conn.SetDeadline(time.Now().Add(5 * 60 * time.Second))
-	err := cli.c.Call(method, args, reply)
-	cli.conn.SetDeadline(time.Time{})
-	return err
+	if err := cli.conn.SetDeadline(time.Now().Add(5 * 60 * time.Second)); err != nil {
+		return err
+	}
+	defer cli.conn.SetDeadline(time.Time{})
+	return cli.c.Call(method, args, reply)
 }
 
 func (cli *RPCClient) Close() {
@@ -103,6 +104,11 @@ func RPCCall(addr, method string, args, reply interface{}) error {
 	return c.Call(method, args, reply)
 }
 
+func setupKeepAlive(conn net.Conn, keepAlive time.Duration) {
+	conn.(*net.TCPConn).SetKeepAlive(true)
+	conn.(*net.TCPConn).SetKeepAlivePeriod(keepAlive)
+}
+
 // flateConn wraps net.Conn in flate.Reader/Writer for compressed traffic.
 type flateConn struct {
 	r io.ReadCloser