Take generic value type

rust-lang · Mar 7, 2022 · d20fc4e · d20fc4e
1 parent 0475e2f
commit d20fc4e
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Showing 3 changed files with 28 additions and 29 deletions.
diff --git a/library/std/src/os/windows/process.rs b/library/std/src/os/windows/process.rs
@@ -4,7 +4,7 @@
 
 #![stable(feature = "process_extensions", since = "1.2.0")]
 
-use crate::ffi::{c_void, OsStr};
+use crate::ffi::OsStr;
 use crate::os::windows::io::{
     AsHandle, AsRawHandle, BorrowedHandle, FromRawHandle, IntoRawHandle, OwnedHandle, RawHandle,
 };
@@ -166,17 +166,14 @@ pub trait CommandExt: Sealed {
     ///
     /// # Safety
     ///
-    /// - The data pointed to by `value` pointer must not be moved or aliased for the entire lifetime of
-    ///   the `Command`.
-    /// - The data pointed to by `value` pointer must be initialized.
-    /// - `size` must not exceed the size of the object pointed to by the `value` pointer.
-    /// - It must be safe to read the data pointed to by `value` from another thread.
+    /// - The attribute and value pair must be supplied in accordance with [Win32 API usage][1].
+    ///
+    /// [1]: https://docs.microsoft.com/en-us/windows/win32/api/processthreadsapi/nf-processthreadsapi-updateprocthreadattribute
     #[unstable(feature = "windows_process_extensions_proc_thread_attributes", issue = "none")]
-    unsafe fn process_thread_attribute(
+    unsafe fn process_thread_attribute<T: Copy + Send + Sync + 'static>(
         &mut self,
         attribute: usize,
-        value: *mut c_void,
-        size: usize,
+        value: T,
     ) -> &mut process::Command;
 }
 
@@ -196,13 +193,12 @@ impl CommandExt for process::Command {
         self.as_inner_mut().raw_arg(raw_text.as_ref());
         self
     }
-    unsafe fn process_thread_attribute(
+    unsafe fn process_thread_attribute<T: Copy + Send + Sync + 'static>(
         &mut self,
         attribute: usize,
-        value: *mut c_void,
-        size: usize,
+        value: T,
     ) -> &mut process::Command {
-        self.as_inner_mut().process_thread_attribute(attribute, value, size);
+        self.as_inner_mut().process_thread_attribute(attribute, value);
         self
     }
 }
diff --git a/library/std/src/process/tests.rs b/library/std/src/process/tests.rs
@@ -412,17 +412,15 @@ fn test_creation_flags() {
 fn test_proc_thread_attributes() {
     use crate::os::windows::io::AsRawHandle;
     use crate::os::windows::process::CommandExt;
-    use crate::sys::c::{DWORD_PTR, HANDLE};
+    use crate::sys::c::DWORD_PTR;
     const PROC_THREAD_ATTRIBUTE_PARENT_PROCESS: DWORD_PTR = 0x00020000;
-    let mut parent = Command::new("cmd.exe").spawn().unwrap();
-    let mut parent_handle: HANDLE = parent.as_raw_handle();
 
+    let mut parent = Command::new("cmd.exe").spawn().unwrap();
     let mut child_cmd = Command::new("cmd.exe");
     unsafe {
         child_cmd.process_thread_attribute(
             PROC_THREAD_ATTRIBUTE_PARENT_PROCESS,
-            &mut parent_handle as *mut _ as *mut _,
-            crate::mem::size_of::<HANDLE>(),
+            parent.as_raw_handle() as isize,
         );
     }
     let mut child = child_cmd.spawn().unwrap();

diff --git a/library/std/src/sys/windows/process.rs b/library/std/src/sys/windows/process.rs
@@ -254,8 +254,15 @@ impl Command {
     pub fn get_current_dir(&self) -> Option<&Path> {
         self.cwd.as_ref().map(|cwd| Path::new(cwd))
     }
-    pub fn process_thread_attribute(&mut self, attribute: usize, ptr: *mut c_void, size: usize) {
-        self.proc_thread_attributes.insert(attribute, ProcThreadAttributeValue { ptr, size });
+    pub unsafe fn process_thread_attribute<T: Copy + Send + Sync + 'static>(
+        &mut self,
+        attribute: usize,
+        value: T,
+    ) {
+        self.proc_thread_attributes.insert(
+            attribute,
+            ProcThreadAttributeValue { size: mem::size_of::<T>(), data: Box::new(value) },
+        );
     }
 
     pub fn spawn(
@@ -876,16 +883,10 @@ impl Drop for ProcThreadAttributeList {
     }
 }
 /// Wrapper around the value data to be used as a Process Thread Attribute.
-/// This exists primarily to force the raw pointer type to be `Send` and `Sync`
-/// without needing to `unsafe impl` them for `Command`.
-#[derive(Copy, Clone)]
 struct ProcThreadAttributeValue {
-    ptr: *mut c_void,
+    data: Box<dyn Send + Sync>,
     size: usize,
 }
-unsafe impl Send for ProcThreadAttributeValue {}
-unsafe impl Sync for ProcThreadAttributeValue {}
-
 fn make_proc_thread_attributes(
     attributes: &BTreeMap<usize, ProcThreadAttributeValue>,
 ) -> io::Result<ProcThreadAttributeList> {
@@ -902,13 +903,17 @@ fn make_proc_thread_attributes(
     // Add our attributes to the buffer.
     // It's theoretically possible for the count to overflow a u32. Therefore, make
     // sure we don't add more attributes than we actually initialized the buffer for.
-    for (&attribute, &value) in attributes.iter().take(count as usize) {
+    for (&attribute, value) in attributes.iter().take(count as usize) {
+        let value_ptr: *const (dyn Send + Sync) = &*value.data as *const _;
+        // let value_ptr = value_ptr as *const _;
+        let value_ptr = value_ptr as *const c_void;
+        let value_ptr = value_ptr as *mut c_void;
         cvt(unsafe {
             c::UpdateProcThreadAttribute(
                 attribute_list.0.as_mut_ptr().cast(),
                 0,
                 attribute,
-                value.ptr,
+                value_ptr,
                 value.size,
                 ptr::null_mut(),
                 ptr::null_mut(),