If poll_oneoff fails part-way through, clean up properly.

Fix the `Drop` implementation for pollables to only drop the pollables
that have been successfully added to the list.

This fixes the poll_oneoff_files failure and removes a FIXME.

Author: sunfishcode

crates/test-programs/wasi-tests/src/bin/poll_oneoff_files.rs

@@ -261,7 +261,7 @@ unsafe fn test_poll_oneoff(dir_fd: wasi::Fd) {
     test_sleep();
     test_empty_poll();
     test_fd_readwrite_valid_fd(dir_fd);
-    //test_fd_readwrite_invalid_fd(); // FIXME: This traps now, rather than failing
+    test_fd_readwrite_invalid_fd();
 }
 fn main() {
     let mut args = env::args();

crates/wasi-preview1-component-adapter/src/lib.rs

@@ -1645,9 +1645,10 @@ impl Pollables {
 // after the call.
 impl Drop for Pollables {
     fn drop(&mut self) {
-        for i in 0..self.length {
+        while self.index != 0 {
+            self.index -= 1;
             unsafe {
-                core::ptr::drop_in_place(self.pointer.add(i));
+                core::ptr::drop_in_place(self.pointer.add(self.index));
             }
         }
     }

crates/wasi-preview1-component-adapter/src/macros.rs

@@ -3,8 +3,8 @@
 //! We're avoiding static initializers, so we can't have things like string
 //! literals. Replace the standard assert macros with simpler implementations.
 
-use crate::bindings::wasi::io::streams;
 use crate::bindings::wasi::cli::stderr::get_stderr;
+use crate::bindings::wasi::io::streams;
 
 #[allow(dead_code)]
 #[doc(hidden)]