make Stat indicate whether it followed a symlink.

R=r
DELTA=61  (34 added, 0 deleted, 27 changed)
OCL=28904
CL=28906

5 files changed, 57 insertions, 23 deletions

diff --git a/src/lib/os/file.go b/src/lib/os/file.go
index 2c609e318..19706e3df 100644
--- a/src/lib/os/file.go
+++ b/src/lib/os/file.go
@@ -194,40 +194,48 @@ func Mkdir(name string, perm int) Error {
 	return ErrnoToError(e)
 }
 
-// Stat returns the Dir structure describing the named file. If the file
-// is a symbolic link, it returns information about the file the link
-// references.
-// It returns the Dir and an error, if any.
+// Stat returns a Dir structure describing the named file and an error, if any.
+// If name names a valid symbolic link, the returned Dir describes
+// the file pointed at by the link and has dir.FollowedSymlink set to true.
+// If name names an invalid symbolic link, the returned Dir describes
+// the link itself and has dir.FollowedSymlink set to false.
 func Stat(name string) (dir *Dir, err Error) {
-	stat := new(syscall.Stat_t);
-	r, e := syscall.Stat(name, stat);
+	var lstat, stat syscall.Stat_t;
+	r, e := syscall.Lstat(name, &lstat);
 	if e != 0 {
-		return nil, ErrnoToError(e)
+		return nil, ErrnoToError(e);
 	}
-	return dirFromStat(name, new(Dir), stat), nil
+	statp := &lstat;
+	if lstat.Mode & syscall.S_IFMT == syscall.S_IFLNK {
+		r, e := syscall.Stat(name, &stat);
+		if e == 0 {
+			statp = &stat;
+		}
+	}
+	return dirFromStat(name, new(Dir), &lstat, statp), nil
 }
 
 // Stat returns the Dir structure describing file.
 // It returns the Dir and an error, if any.
 func (file *File) Stat() (dir *Dir, err Error) {
-	stat := new(syscall.Stat_t);
-	r, e := syscall.Fstat(file.fd, stat);
+	var stat syscall.Stat_t;
+	r, e := syscall.Fstat(file.fd, &stat);
 	if e != 0 {
 		return nil, ErrnoToError(e)
 	}
-	return dirFromStat(file.name, new(Dir), stat), nil
+	return dirFromStat(file.name, new(Dir), &stat, &stat), nil
 }
 
-// Lstat returns the Dir structure describing the named file. If the file
-// is a symbolic link, it returns information about the link itself.
-// It returns the Dir and an error, if any.
+// Lstat returns the Dir structure describing the named file and an error, if any.
+// If the file is a symbolic link, the returned Dir describes the
+// symbolic link.  Lstat makes no attempt to follow the link.
 func Lstat(name string) (dir *Dir, err Error) {
-	stat := new(syscall.Stat_t);
-	r, e := syscall.Lstat(name, stat);
+	var stat syscall.Stat_t;
+	r, e := syscall.Lstat(name, &stat);
 	if e != 0 {
 		return nil, ErrnoToError(e)
 	}
-	return dirFromStat(name, new(Dir), stat), nil
+	return dirFromStat(name, new(Dir), &stat, &stat), nil
 }
 
 // Readdirnames has a non-portable implemenation so its code is separated into an
@@ -238,16 +246,16 @@ func readdirnames(file *File, count int) (names []string, err Error)
 // returns an array of up to count names, in directory order.  Subsequent
 // calls on the same file will yield further names.
 // A negative count means to read until EOF.
-// It returns the array and an Error, if any.
+// Readdirnames returns the array and an Error, if any.
 func (file *File) Readdirnames(count int) (names []string, err Error) {
 	return readdirnames(file, count);
 }
 
 // Readdir reads the contents of the directory associated with file and
-// returns an array of up to count Dir structures, in directory order.  Subsequent
-// calls on the same file will yield further Dirs.
+// returns an array of up to count Dir structures, as would be returned
+// by Stat, in directory order.  Subsequent calls on the same file will yield further Dirs.
 // A negative count means to read until EOF.
-// It returns the array and an Error, if any.
+// Readdir returns the array and an Error, if any.
 func (file *File) Readdir(count int) (dirs []Dir, err Error) {
 	dirname := file.name;
 	if dirname == "" {
diff --git a/src/lib/os/os_test.go b/src/lib/os/os_test.go
index 7c503bfe6..5c2d68617 100644
--- a/src/lib/os/os_test.go
+++ b/src/lib/os/os_test.go
@@ -255,6 +255,9 @@ func TestSymLink(t *testing.T) {
 	if err != nil {
 		t.Fatalf("stat %q failed: %v", to, err);
 	}
+	if tostat.FollowedSymlink {
+		t.Fatalf("stat %q claims to have followed a symlink", to);
+	}
 	fromstat, err := Stat(from);
 	if err != nil {
 		t.Fatalf("stat %q failed: %v", from, err);
@@ -269,6 +272,13 @@ func TestSymLink(t *testing.T) {
 	if !fromstat.IsSymlink() {
 		t.Fatalf("symlink %q, %q did not create symlink", to, from);
 	}
+	fromstat, err = Stat(from);
+	if err != nil {
+		t.Fatalf("stat %q failed: %v", from, err);
+	}
+	if !fromstat.FollowedSymlink {
+		t.Fatalf("stat %q did not follow symlink");
+	}
 	s, err := Readlink(from);
 	if err != nil {
 		t.Fatalf("readlink %q failed: %v", from, err);
diff --git a/src/lib/os/stat_amd64_darwin.go b/src/lib/os/stat_amd64_darwin.go
index 0c811680a..e72d76f91 100644
--- a/src/lib/os/stat_amd64_darwin.go
+++ b/src/lib/os/stat_amd64_darwin.go
@@ -9,7 +9,11 @@ package os
 import syscall "syscall"
 import os "os"
 
-func dirFromStat(name string, dir *Dir, stat *syscall.Stat_t) *Dir {
+func isSymlink(stat *syscall.Stat_t) bool {
+	return stat.Mode & syscall.S_IFMT == syscall.S_IFLNK
+}
+
+func dirFromStat(name string, dir *Dir, lstat, stat *syscall.Stat_t) *Dir {
 	dir.Dev = uint64(stat.Dev);
 	dir.Ino = stat.Ino;
 	dir.Nlink = uint64(stat.Nlink);
@@ -30,5 +34,8 @@ func dirFromStat(name string, dir *Dir, stat *syscall.Stat_t) *Dir {
 		}
 	}
 	dir.Name = name;
+	if isSymlink(lstat) && !isSymlink(stat) {
+		dir.FollowedSymlink = true;
+	}
 	return dir;
 }
diff --git a/src/lib/os/stat_amd64_linux.go b/src/lib/os/stat_amd64_linux.go
index b39f8c2ad..e1beb1666 100644
--- a/src/lib/os/stat_amd64_linux.go
+++ b/src/lib/os/stat_amd64_linux.go
@@ -9,7 +9,11 @@ package os
 import syscall "syscall"
 import os "os"
 
-func dirFromStat(name string, dir *Dir, stat *syscall.Stat_t) *Dir {
+func isSymlink(stat *syscall.Stat_t) bool {
+	return stat.Mode & syscall.S_IFMT == syscall.S_IFLNK
+}
+
+func dirFromStat(name string, dir *Dir, lstat, stat *syscall.Stat_t) *Dir {
 	dir.Dev = stat.Dev;
 	dir.Ino = stat.Ino;
 	dir.Nlink = stat.Nlink;
@@ -30,5 +34,8 @@ func dirFromStat(name string, dir *Dir, stat *syscall.Stat_t) *Dir {
 		}
 	}
 	dir.Name = name;
+	if isSymlink(lstat) && !isSymlink(stat) {
+		dir.FollowedSymlink = true;
+	}
 	return dir;
 }
diff --git a/src/lib/os/types.go b/src/lib/os/types.go
index aba463199..73363f453 100644
--- a/src/lib/os/types.go
+++ b/src/lib/os/types.go
@@ -25,6 +25,7 @@ type Dir struct {
 	Mtime_ns	uint64;	// modified time; nanoseconds since epoch.
 	Ctime_ns	uint64;	// status change time; nanoseconds since epoch.
 	Name	string;	// name of file as presented to Open.
+	FollowedSymlink	bool;		// followed a symlink to get this information
 }
 
 // IsFifo reports whether the Dir describes a FIFO file.
@@ -66,3 +67,4 @@ func (dir *Dir) IsSocket() bool {
 func (dir *Dir) Permission() int {
 	return int(dir.Mode & 0777)
 }
+