os: in Getwd, $PWD override syscall.Getwd

This makes os.Getwd mimic C getwd on OS X,
and possibly other systems. The change on OS X
was a regression from 1.2 to 1.3.

Fixes #8400.

LGTM=bradfitz
R=iant, bradfitz
CC=golang-codereviews
https://golang.org/cl/118970043

diff --git a/src/pkg/os/getwd.go b/src/pkg/os/getwd.go
index a72edeaee6e446cff958ef63a3830fd202e09a78..eacb414660ac8e74b3c04bc4e90b80a094cbc64c 100644 (file)
--- a/src/pkg/os/getwd.go
+++ b/src/pkg/os/getwd.go
@@ -23,22 +23,12 @@ var useSyscallwd = func(error) bool { return true }
 // reached via multiple paths (due to symbolic links),
 // Getwd may return any one of them.
 func Getwd() (dir string, err error) {
-       // If the operating system provides a Getwd call, use it.
-       if syscall.ImplementsGetwd {
-               s, e := syscall.Getwd()
-               if useSyscallwd(e) {
-                       return s, NewSyscallError("getwd", e)
-               }
-       }
-
-       // Otherwise, we're trying to find our way back to ".".
+       // Clumsy but widespread kludge:
+       // if $PWD is set and matches ".", use it.
        dot, err := Stat(".")
        if err != nil {
                return "", err
        }
-
-       // Clumsy but widespread kludge:
-       // if $PWD is set and matches ".", use it.
        dir = Getenv("PWD")
        if len(dir) > 0 && dir[0] == '/' {
                d, err := Stat(dir)
@@ -47,6 +37,15 @@ func Getwd() (dir string, err error) {
                }
        }
 
+       // If the operating system provides a Getwd call, use it.
+       // Otherwise, we're trying to find our way back to ".".
+       if syscall.ImplementsGetwd {
+               s, e := syscall.Getwd()
+               if useSyscallwd(e) {
+                       return s, NewSyscallError("getwd", e)
+               }
+       }
+
        // Apply same kludge but to cached dir instead of $PWD.
        getwdCache.Lock()
        dir = getwdCache.dir

diff --git a/src/pkg/os/os_test.go b/src/pkg/os/os_test.go
index 2811f29f348ffbdd5fbd2f38e9e19bd066bf5626..0224c9b01d60f5592a8132949f9a8e5e1dee2e7b 100644 (file)
--- a/src/pkg/os/os_test.go
+++ b/src/pkg/os/os_test.go
@@ -811,8 +811,8 @@ func TestChdirAndGetwd(t *testing.T) {
                t.Fatalf("Open .: %s", err)
        }
        // These are chosen carefully not to be symlinks on a Mac
-       // (unlike, say, /var, /etc, and /tmp).
-       dirs := []string{"/", "/usr/bin"}
+       // (unlike, say, /var, /etc), except /tmp, which we handle below.
+       dirs := []string{"/", "/usr/bin", "/tmp"}
        // /usr/bin does not usually exist on Plan 9 or Android.
        switch runtime.GOOS {
        case "android":
@@ -820,6 +820,7 @@ func TestChdirAndGetwd(t *testing.T) {
        case "plan9":
                dirs = []string{"/", "/usr"}
        }
+       oldwd := Getenv("PWD")
        for mode := 0; mode < 2; mode++ {
                for _, d := range dirs {
                        if mode == 0 {
@@ -833,7 +834,11 @@ func TestChdirAndGetwd(t *testing.T) {
                                err = fd1.Chdir()
                                fd1.Close()
                        }
+                       if d == "/tmp" {
+                               Setenv("PWD", "/tmp")
+                       }
                        pwd, err1 := Getwd()
+                       Setenv("PWD", oldwd)
                        err2 := fd.Chdir()
                        if err2 != nil {
                                // We changed the current directory and cannot go back.