Improve gccgo compatibility

Still fails, but with a clearer error message:

$ go.gcc build
internal/syscallcompat/unix2syscall_linux.go:32:13: error: incompatible types in assignment (cannot use type int64 as type syscall.Timespec_sec_t)
  s.Atim.Sec = u.Atim.Sec
             ^
internal/syscallcompat/unix2syscall_linux.go:33:14: error: incompatible types in assignment (cannot use type int64 as type syscall.Timespec_nsec_t)
  s.Atim.Nsec = u.Atim.Nsec
              ^
internal/syscallcompat/unix2syscall_linux.go:35:13: error: incompatible types in assignment (cannot use type int64 as type syscall.Timespec_sec_t)
  s.Mtim.Sec = u.Mtim.Sec
             ^
internal/syscallcompat/unix2syscall_linux.go:36:14: error: incompatible types in assignment (cannot use type int64 as type syscall.Timespec_nsec_t)
  s.Mtim.Nsec = u.Mtim.Nsec
              ^
internal/syscallcompat/unix2syscall_linux.go:38:13: error: incompatible types in assignment (cannot use type int64 as type syscall.Timespec_sec_t)
  s.Ctim.Sec = u.Ctim.Sec
             ^
internal/syscallcompat/unix2syscall_linux.go:39:14: error: incompatible types in assignment (cannot use type int64 as type syscall.Timespec_nsec_t)
  s.Ctim.Nsec = u.Ctim.Nsec
              ^

internal/fusefrontend_reverse/ctlsock_interface.go

@@ -3,7 +3,8 @@ package fusefrontend_reverse
 import (
 	"path/filepath"
 	"strings"
-	"syscall"
+
+	"golang.org/x/sys/unix"
 
 	"github.com/rfjakob/gocryptfs/internal/ctlsock"
 	"github.com/rfjakob/gocryptfs/internal/pathiv"
@@ -23,7 +24,7 @@ func (rfs *ReverseFS) EncryptPath(plainPath string) (string, error) {
 	for _, part := range parts {
 		dirIV := pathiv.Derive(cipherPath, pathiv.PurposeDirIV)
 		encryptedPart := rfs.nameTransform.EncryptName(part, dirIV)
-		if rfs.args.LongNames && len(encryptedPart) > syscall.NAME_MAX {
+		if rfs.args.LongNames && len(encryptedPart) > unix.NAME_MAX {
 			encryptedPart = rfs.nameTransform.HashLongName(encryptedPart)
 		}
 		cipherPath = filepath.Join(cipherPath, encryptedPart)

internal/fusefrontend_reverse/reverse_longnames.go

@@ -7,6 +7,8 @@ import (
 	"syscall"
 	"time"
 
+	"golang.org/x/sys/unix"
+
 	"github.com/hanwen/go-fuse/fuse"
 	"github.com/hanwen/go-fuse/fuse/nodefs"
 
@@ -80,7 +82,7 @@ func (rfs *ReverseFS) findLongnameParent(dir string, dirIV []byte, longname stri
 			continue
 		}
 		cName := rfs.nameTransform.EncryptName(plaintextName, dirIV)
-		if len(cName) <= syscall.NAME_MAX {
+		if len(cName) <= unix.NAME_MAX {
 			// Entry should have been skipped by the "continue" above
 			log.Panic("logic error or wrong shortNameMax constant?")
 		}

internal/syscallcompat/unix2syscall_linux.go

@@ -10,7 +10,7 @@ import (
 // A direct cast does not work because the padding is named differently in
 // unix.Stat_t for some reason ("X__unused" in syscall, "_" in unix).
 func Unix2syscall(u unix.Stat_t) syscall.Stat_t {
-	return syscall.Stat_t{
+	s := syscall.Stat_t{
 		Dev:     u.Dev,
 		Ino:     u.Ino,
 		Nlink:   u.Nlink,
@@ -21,8 +21,22 @@ func Unix2syscall(u unix.Stat_t) syscall.Stat_t {
 		Size:    u.Size,
 		Blksize: u.Blksize,
 		Blocks:  u.Blocks,
-		Atim:    syscall.Timespec(u.Atim),
-		Mtim:    syscall.Timespec(u.Mtim),
-		Ctim:    syscall.Timespec(u.Ctim),
+		// Casting unix.Timespec to syscall.Timespec does not work on gccgo:
+		// > cannot use type int64 as type syscall.Timespec_sec_t
+		// So do it manually, element-wise.
+		//
+		//Atim:   syscall.Timespec(u.Atim),
+		//Mtim:   syscall.Timespec(u.Mtim),
+		//Ctim:   syscall.Timespec(u.Ctim),
 	}
+	s.Atim.Sec = u.Atim.Sec
+	s.Atim.Nsec = u.Atim.Nsec
+
+	s.Mtim.Sec = u.Mtim.Sec
+	s.Mtim.Nsec = u.Mtim.Nsec
+
+	s.Ctim.Sec = u.Ctim.Sec
+	s.Ctim.Nsec = u.Ctim.Nsec
+
+	return s
 }