os: do not skip directory entries with zero inodes on wasip1

When building programs to GOOS=wasip1, the program does not have the
guarantees that the underlying directories will come from a file system
where a zero inode value indicates that the entry was deleted but not
yet removed from the directory. The host runtime may be running on
windows or may be exposing virtual user-space file systems that do not
have the concept of inodes. In those setup, we assume that the host
runtime is in charge of dealing with edge cases such as skipping
directory entries with zero inodes when needed, and the guest
application should trust the list of entries that it sees;
therefore, we disable skipping over zero inodes on wasip1.

Change-Id: I99aa562441cdb4182965f270af054cf3cf7f8f20
Reviewed-on: https://go-review.googlesource.com/c/go/+/507915
Reviewed-by: Ian Lance Taylor <[email protected]>
Run-TryBot: Ian Lance Taylor <[email protected]>
Auto-Submit: Ian Lance Taylor <[email protected]>
TryBot-Result: Gopher Robot <[email protected]>
Reviewed-by: Dmitri Shuralyov <[email protected]>
Reviewed-by: Johan Brandhorst-Satzkorn <[email protected]>

src/os/dir_darwin.go

@@ -54,6 +54,15 @@ func (f *File) readdir(n int, mode readdirMode) (names []string, dirents []DirEn
 		if entptr == nil { // EOF
 			break
 		}
+		// Darwin may return a zero inode when a directory entry has been
+		// deleted but not yet removed from the directory. The man page for
+		// getdirentries(2) states that programs are responsible for skipping
+		// those entries:
+		//
+		//   Users of getdirentries() should skip entries with d_fileno = 0,
+		//   as such entries represent files which have been deleted but not
+		//   yet removed from the directory entry.
+		//
 		if dirent.Ino == 0 {
 			continue
 		}

src/os/dir_unix.go

@@ -89,7 +89,11 @@ func (f *File) readdir(n int, mode readdirMode) (names []string, dirents []DirEn
 		if !ok {
 			break
 		}
-		if ino == 0 {
+		// When building to wasip1, the host runtime might be running on Windows
+		// or might expose a remote file system which does not have the concept
+		// of inodes. Therefore, we cannot make the assumption that it is safe
+		// to skip entries with zero inodes.
+		if ino == 0 && runtime.GOOS != "wasip1" {
 			continue
 		}
 		const namoff = uint64(unsafe.Offsetof(syscall.Dirent{}.Name))

src/syscall/dirent.go

@@ -6,7 +6,10 @@
 
 package syscall
 
-import "unsafe"
+import (
+	"runtime"
+	"unsafe"
+)
 
 // readInt returns the size-bytes unsigned integer in native byte order at offset off.
 func readInt(b []byte, off, size uintptr) (u uint64, ok bool) {
@@ -75,7 +78,9 @@ func ParseDirent(buf []byte, max int, names []string) (consumed int, count int,
 		if !ok {
 			break
 		}
-		if ino == 0 { // File absent in directory.
+		// See src/os/dir_unix.go for the reason why this condition is
+		// excluded on wasip1.
+		if ino == 0 && runtime.GOOS != "wasip1" { // File absent in directory.
 			continue
 		}
 		const namoff = uint64(unsafe.Offsetof(Dirent{}.Name))