os: treat Getwd result of ENOMEM the same as ENAMETOOLONG

We can see ENOMEM on FreeBSD.

Also don't fail the test if we get an EPERM error when reading
all the way up the tree; on Android we get that, perhaps because
the root directory is unreadable.

Also accept an EFAULT from a stat of a long name on Dragonfly,
which we see on the builders.

Change-Id: If37e6bf414b7b568c9a06130f71e79af153bfb75
Reviewed-on: https://go-review.googlesource.com/c/go/+/610415
Auto-Submit: Ian Lance Taylor <[email protected]>
Reviewed-by: Keith Randall <[email protected]>
LUCI-TryBot-Result: Go LUCI <[email protected]>
Reviewed-by: Ian Lance Taylor <[email protected]>
Commit-Queue: Ian Lance Taylor <[email protected]>
Reviewed-by: Keith Randall <[email protected]>

Author: ianlancetaylor

src/os/error_errno.go

@@ -10,5 +10,8 @@ import "syscall"
 
 type syscallErrorType = syscall.Errno
 
-const errENOSYS = syscall.ENOSYS
-const errERANGE = syscall.ERANGE
+const (
+	errENOSYS = syscall.ENOSYS
+	errERANGE = syscall.ERANGE
+	errENOMEM = syscall.ENOMEM
+)

src/os/error_plan9.go

@@ -10,3 +10,4 @@ type syscallErrorType = syscall.ErrorString
 
 var errENOSYS = syscall.NewError("function not implemented")
 var errERANGE = syscall.NewError("out of range")
+var errENOMEM = syscall.NewError("cannot allocate memory")

src/os/getwd.go

@@ -60,9 +60,10 @@ func Getwd() (dir string, err error) {
 			}
 		}
 		// Linux returns ENAMETOOLONG if the result is too long.
-		// BSD systems appear to return EINVAL.
+		// Some BSD systems appear to return EINVAL.
+		// FreeBSD systems appear to use ENOMEM
 		// Solaris appears to use ERANGE.
-		if err != syscall.ENAMETOOLONG && err != syscall.EINVAL && err != errERANGE {
+		if err != syscall.ENAMETOOLONG && err != syscall.EINVAL && err != errERANGE && err != errENOMEM {
 			return dir, NewSyscallError("getwd", err)
 		}
 	}

src/os/getwd_unix_test.go

@@ -9,6 +9,7 @@ package os_test
 import (
 	"errors"
 	. "os"
+	"runtime"
 	"strings"
 	"syscall"
 	"testing"
@@ -56,6 +57,12 @@ func testGetwdDeep(t *testing.T, setPWD bool) {
 		wd, err := Getwd()
 		t.Logf("Getwd len: %d", len(wd))
 		if err != nil {
+			// We can get an EPERM error if we can't read up
+			// to root, which happens on the Android builders.
+			if errors.Is(err, syscall.EPERM) {
+				t.Logf("ignoring EPERM error: %v", err)
+				break
+			}
 			t.Fatal(err)
 		}
 		if setPWD && wd != dir {
@@ -72,7 +79,13 @@ func testGetwdDeep(t *testing.T, setPWD bool) {
 		// all Unix platforms (4096, on Linux).
 		if _, err := Stat(wd); err != nil || len(wd) > 4096 {
 			t.Logf("Done; len(wd)=%d", len(wd))
-			if err != nil && !errors.Is(err, syscall.ENAMETOOLONG) {
+			// Most systems return ENAMETOOLONG.
+			// Dragonfly returns EFAULT.
+			switch {
+			case err == nil:
+			case errors.Is(err, syscall.ENAMETOOLONG):
+			case runtime.GOOS == "dragonfly" && errors.Is(err, syscall.EFAULT):
+			default:
 				t.Fatalf("unexpected Stat error: %v", err)
 			}
 			break