Remove needs_close from FdObject

This commit removes `needs_close` field from `FdObject`, and
stores the underlying `Descriptor` without the `ManuallyDrop`
wrapper.

src/fdentry.rs

@@ -1,6 +1,5 @@
 use crate::sys::fdentry_impl::{determine_type_and_access_rights, OsFile};
 use crate::{host, Error, Result};
-use std::mem::ManuallyDrop;
 use std::path::PathBuf;
 use std::{fs, io};
 
@@ -62,8 +61,7 @@ impl Descriptor {
 #[derive(Debug)]
 pub(crate) struct FdObject {
     pub(crate) file_type: host::__wasi_filetype_t,
-    pub(crate) descriptor: ManuallyDrop<Descriptor>,
-    pub(crate) needs_close: bool,
+    pub(crate) descriptor: Descriptor,
     // TODO: directories
 }
 
@@ -75,22 +73,13 @@ pub(crate) struct FdEntry {
     pub(crate) preopen_path: Option<PathBuf>,
 }
 
-impl Drop for FdObject {
-    fn drop(&mut self) {
-        if self.needs_close {
-            unsafe { ManuallyDrop::drop(&mut self.descriptor) };
-        }
-    }
-}
-
 impl FdEntry {
     pub(crate) fn from(file: fs::File) -> Result<Self> {
         unsafe { determine_type_and_access_rights(&file) }.map(
             |(file_type, rights_base, rights_inheriting)| Self {
                 fd_object: FdObject {
                     file_type,
-                    descriptor: ManuallyDrop::new(Descriptor::OsFile(OsFile::from(file))),
-                    needs_close: true,
+                    descriptor: Descriptor::OsFile(OsFile::from(file)),
                 },
                 rights_base,
                 rights_inheriting,
@@ -108,8 +97,7 @@ impl FdEntry {
             |(file_type, rights_base, rights_inheriting)| Self {
                 fd_object: FdObject {
                     file_type,
-                    descriptor: ManuallyDrop::new(Descriptor::Stdin),
-                    needs_close: true,
+                    descriptor: Descriptor::Stdin,
                 },
                 rights_base,
                 rights_inheriting,
@@ -123,8 +111,7 @@ impl FdEntry {
             |(file_type, rights_base, rights_inheriting)| Self {
                 fd_object: FdObject {
                     file_type,
-                    descriptor: ManuallyDrop::new(Descriptor::Stdout),
-                    needs_close: true,
+                    descriptor: Descriptor::Stdout,
                 },
                 rights_base,
                 rights_inheriting,
@@ -138,8 +125,7 @@ impl FdEntry {
             |(file_type, rights_base, rights_inheriting)| Self {
                 fd_object: FdObject {
                     file_type,
-                    descriptor: ManuallyDrop::new(Descriptor::Stderr),
-                    needs_close: true,
+                    descriptor: Descriptor::Stderr,
                 },
                 rights_base,
                 rights_inheriting,

src/hostcalls_impl/fs.rs

@@ -24,9 +24,7 @@ pub(crate) unsafe fn fd_close(wasi_ctx: &mut WasiCtx, fd: wasm32::__wasi_fd_t) -
         }
     }
 
-    let mut fe = wasi_ctx.fds.remove(&fd).ok_or(Error::EBADF)?;
-    fe.fd_object.needs_close = true;
-
+    wasi_ctx.fds.remove(&fd).ok_or(Error::EBADF)?;
     Ok(())
 }
 
@@ -158,7 +156,7 @@ pub(crate) unsafe fn fd_read(
         .map(|vec| host::iovec_to_host_mut(vec))
         .collect();
 
-    let maybe_host_nread = match &mut *fe.fd_object.descriptor {
+    let maybe_host_nread = match &mut fe.fd_object.descriptor {
         Descriptor::OsFile(file) => file.read_vectored(&mut iovs),
         Descriptor::Stdin => io::stdin().lock().read_vectored(&mut iovs),
         _ => return Err(Error::EBADF),
@@ -374,7 +372,7 @@ pub(crate) unsafe fn fd_write(
     let iovs: Vec<io::IoSlice> = iovs.iter().map(|vec| host::iovec_to_host(vec)).collect();
 
     // perform unbuffered writes
-    let host_nwritten = match &mut *fe.fd_object.descriptor {
+    let host_nwritten = match &mut fe.fd_object.descriptor {
         Descriptor::OsFile(file) => file.write_vectored(&iovs)?,
         Descriptor::Stdin => return Err(Error::EBADF),
         Descriptor::Stdout => {