Add test for dangling file/dir handles (#566)

* Add test for dangling file/dir handles

This commit adds a test for dangling file/dir handles. The logic is
quite simple: we first create a resource (file or dir), get a WASI file
descriptor to it, remove the resource without closing the FD, and then
try to re-create it.

* Disable on Windows for now

crates/test-programs/build.rs

@@ -168,6 +168,7 @@ cfg_if::cfg_if! {
                     "truncation_rights" => true,
                     "poll_oneoff" => true,
                     "path_link" => true,
+                    "dangling_fd" => true,
                     _ => false,
                 }
             } else {

crates/wasi-common/wasi-misc-tests/src/bin/dangling_fd.rs

@@ -0,0 +1,96 @@
+use more_asserts::assert_gt;
+use std::{env, process};
+use wasi::wasi_unstable;
+use wasi_misc_tests::open_scratch_directory;
+use wasi_misc_tests::utils::{cleanup_dir, cleanup_file, create_dir, create_file};
+use wasi_misc_tests::wasi_wrappers::wasi_path_open;
+
+unsafe fn create_or_open(
+    dir_fd: wasi_unstable::Fd,
+    name: &str,
+    flags: wasi_unstable::OFlags,
+) -> wasi_unstable::Fd {
+    let mut file_fd = wasi_unstable::Fd::max_value() - 1;
+    let mut status = wasi_path_open(dir_fd, 0, name, flags, 0, 0, 0, &mut file_fd);
+    assert_eq!(
+        status,
+        wasi_unstable::raw::__WASI_ESUCCESS,
+        "opening '{}'",
+        name
+    );
+    assert_gt!(
+        file_fd,
+        libc::STDERR_FILENO as wasi_unstable::Fd,
+        "file descriptor range check",
+    );
+    file_fd
+}
+
+unsafe fn test_dangling_fd(dir_fd: wasi_unstable::Fd) {
+    // Create a file, open it, delete it without closing the handle,
+    // and then try creating it again
+    create_file(dir_fd, "file");
+    let mut file_fd = wasi_unstable::Fd::max_value() - 1;
+    let mut status = wasi_path_open(dir_fd, 0, "file", 0, 0, 0, 0, &mut file_fd);
+    assert_eq!(
+        status,
+        wasi_unstable::raw::__WASI_ESUCCESS,
+        "opening a file",
+    );
+    assert_gt!(
+        file_fd,
+        libc::STDERR_FILENO as wasi_unstable::Fd,
+        "file descriptor range check",
+    );
+    cleanup_file(dir_fd, "file");
+    create_file(dir_fd, "file");
+
+    // Now, repeat the same process but for a directory
+    create_dir(dir_fd, "subdir");
+    let mut subdir_fd = wasi_unstable::Fd::max_value() - 1;
+    let mut status = wasi_path_open(
+        dir_fd,
+        0,
+        "subdir",
+        wasi_unstable::O_DIRECTORY,
+        0,
+        0,
+        0,
+        &mut subdir_fd,
+    );
+    assert_eq!(
+        status,
+        wasi_unstable::raw::__WASI_ESUCCESS,
+        "opening a directory",
+    );
+    assert_gt!(
+        file_fd,
+        libc::STDERR_FILENO as wasi_unstable::Fd,
+        "file descriptor range check",
+    );
+    cleanup_dir(dir_fd, "subdir");
+    create_dir(dir_fd, "subdir");
+}
+
+fn main() {
+    let mut args = env::args();
+    let prog = args.next().unwrap();
+    let arg = if let Some(arg) = args.next() {
+        arg
+    } else {
+        eprintln!("usage: {} <scratch directory>", prog);
+        process::exit(1);
+    };
+
+    // Open scratch directory
+    let dir_fd = match open_scratch_directory(&arg) {
+        Ok(dir_fd) => dir_fd,
+        Err(err) => {
+            eprintln!("{}", err);
+            process::exit(1)
+        }
+    };
+
+    // Run the tests.
+    unsafe { test_dangling_fd(dir_fd) }
+}