Implement Sync for `process::Command on unix and vxworks

src/libstd/process.rs

@@ -2105,8 +2105,8 @@ mod tests {
     }
 
     #[test]
-    fn test_command_implements_send() {
+    fn test_command_implements_send_sync() {
-        fn take_send_type<T: Send>(_: T) {}
+        fn take_send_sync_type<T: Send + Sync>(_: T) {}
-        take_send_type(Command::new(""))
+        take_send_sync_type(Command::new(""))
     }
 }

src/libstd/sys/unix/process/process_common.rs

@@ -86,11 +86,13 @@ pub struct Command {
     stderr: Option<Stdio>,
 }
 
-// Create a new type for argv, so that we can make it `Send`
+// Create a new type for argv, so that we can make it `Send` and `Sync`
 struct Argv(Vec<*const c_char>);
 
-// It is safe to make Argv Send, because it contains pointers to memory owned by `Command.args`
+// It is safe to make `Argv` `Send` and `Sync`, because it contains
+// pointers to memory owned by `Command.args`
 unsafe impl Send for Argv {}
+unsafe impl Sync for Argv {}
 
 // passed back to std::process with the pipes connected to the child, if any
 // were requested

src/libstd/sys/vxworks/process/process_common.rs

@@ -49,11 +49,13 @@ pub struct Command {
     stderr: Option<Stdio>,
 }
 
-// Create a new type for argv, so that we can make it `Send`
+// Create a new type for `Argv`, so that we can make it `Send` and `Sync`
 struct Argv(Vec<*const c_char>);
 
-// It is safe to make Argv Send, because it contains pointers to memory owned by `Command.args`
+// It is safe to make `Argv` `Send` and `Sync`, because it contains
+// pointers to memory owned by `Command.args`
 unsafe impl Send for Argv {}
+unsafe impl Sync for Argv {}
 
 // passed back to std::process with the pipes connected to the child, if any
 // were requested