From cda8656d59e2c7da843daaa54868530d811cefa9 Mon Sep 17 00:00:00 2001
From: "Jeong, YunWon" <jeong@youknowone.org>
Date: Fri, 20 Feb 2026 18:23:15 +0900
Subject: [PATCH] Fix Overlapped I/O by boxing OVERLAPPED struct and accept
 overlapped arg positionally

Two fixes in _winapi:

1. Box the OVERLAPPED struct in OverlappedInner to ensure it stays at
   a stable heap address. Previously, into_pyobject() moved the struct
   after ReadFile/WriteFile had given the OS a pointer to it, causing
   GetOverlappedResult to read stale data (returning err=0 instead of
   ERROR_MORE_DATA for zero-byte reads on message pipes).

2. Change ReadFile, WriteFile, ConnectNamedPipe overlapped parameter
   from #[pyarg(named)] to #[pyarg(any)] so it can be passed both
   positionally and as keyword argument.
---
 crates/vm/src/stdlib/_winapi.rs | 34 ++++++++++++++++++---------------
 1 file changed, 19 insertions(+), 15 deletions(-)

diff --git a/crates/vm/src/stdlib/_winapi.rs b/crates/vm/src/stdlib/_winapi.rs
index 98299c671e9..580300b2b7b 100644
--- a/crates/vm/src/stdlib/_winapi.rs
+++ b/crates/vm/src/stdlib/_winapi.rs
@@ -800,7 +800,11 @@ mod _winapi {
     }
 
     struct OverlappedInner {
-        overlapped: windows_sys::Win32::System::IO::OVERLAPPED,
+        // Box ensures the OVERLAPPED struct stays at a stable heap address
+        // even when the containing Overlapped Python object is moved during
+        // into_pyobject(). The OS holds a pointer to this struct for pending
+        // I/O operations, so it must not be relocated.
+        overlapped: Box<windows_sys::Win32::System::IO::OVERLAPPED>,
         handle: HANDLE,
         pending: bool,
         completed: bool,
@@ -833,7 +837,7 @@ mod _winapi {
 
             Overlapped {
                 inner: PyMutex::new(OverlappedInner {
-                    overlapped,
+                    overlapped: Box::new(overlapped),
                     handle,
                     pending: false,
                     completed: false,
@@ -858,7 +862,7 @@ mod _winapi {
             let ret = unsafe {
                 GetOverlappedResult(
                     inner.handle,
-                    &inner.overlapped,
+                    &*inner.overlapped,
                     &mut transferred,
                     if wait { 1 } else { 0 },
                 )
@@ -913,7 +917,7 @@ mod _winapi {
 
             let mut inner = self.inner.lock();
             let ret = if inner.pending {
-                unsafe { CancelIoEx(inner.handle, &inner.overlapped) }
+                unsafe { CancelIoEx(inner.handle, &*inner.overlapped) }
             } else {
                 1
             };
@@ -958,9 +962,9 @@ mod _winapi {
     /// ConnectNamedPipe - Wait for a client to connect to a named pipe
     #[derive(FromArgs)]
     struct ConnectNamedPipeArgs {
-        #[pyarg(positional)]
+        #[pyarg(any)]
         handle: WinHandle,
-        #[pyarg(named, optional)]
+        #[pyarg(any, optional)]
         overlapped: OptionalArg<bool>,
     }
 
@@ -982,7 +986,7 @@ mod _winapi {
                 unsafe {
                     windows_sys::Win32::System::Pipes::ConnectNamedPipe(
                         handle.0,
-                        &mut inner.overlapped,
+                        &mut *inner.overlapped,
                     )
                 }
             };
@@ -1200,11 +1204,11 @@ mod _winapi {
 
     #[derive(FromArgs)]
     struct WriteFileArgs {
-        #[pyarg(positional)]
+        #[pyarg(any)]
         handle: WinHandle,
-        #[pyarg(positional)]
+        #[pyarg(any)]
         buffer: crate::function::ArgBytesLike,
-        #[pyarg(named, default = false)]
+        #[pyarg(any, default = false)]
         overlapped: bool,
     }
 
@@ -1233,7 +1237,7 @@ mod _winapi {
                         write_buf.as_ptr() as *const _,
                         len,
                         &mut written,
-                        &mut inner.overlapped,
+                        &mut *inner.overlapped,
                     )
                 };
 
@@ -1287,11 +1291,11 @@ mod _winapi {
 
     #[derive(FromArgs)]
     struct ReadFileArgs {
-        #[pyarg(positional)]
+        #[pyarg(any)]
         handle: WinHandle,
-        #[pyarg(positional)]
+        #[pyarg(any)]
         size: u32,
-        #[pyarg(named, default = false)]
+        #[pyarg(any, default = false)]
         overlapped: bool,
     }
 
@@ -1319,7 +1323,7 @@ mod _winapi {
                         read_buf.as_mut_ptr() as *mut _,
                         size,
                         &mut nread,
-                        &mut inner.overlapped,
+                        &mut *inner.overlapped,
                     )
                 };