Implement TryEnterCriticalSection

Author: divergentdave

src/shims/foreign_items/windows.rs

@@ -233,6 +233,11 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx
                 // (Windows locks are reentrant, and we have only 1 thread,
                 // so not doing any futher checks here is at least not incorrect.)
             }
+            "TryEnterCriticalSection" if this.frame().instance.to_string().starts_with("std::sys::windows::")
+            => {
+                // There is only one thread, so this always succeeds and returns TRUE
+                this.write_scalar(Scalar::from_int(1, dest.layout.size), dest)?;
+            }
 
             _ => throw_unsup_format!("can't call foreign function: {}", link_name),
         }

tests/run-pass/sync.rs

@@ -1,6 +1,6 @@
 #![feature(rustc_private)]
 
-use std::sync::{Mutex, RwLock, TryLockError};
+use std::sync::{Mutex, TryLockError};
 
 extern crate libc;
 
@@ -86,6 +86,7 @@ fn test_mutex_libc_static_initializer_recursive() {
 
 #[cfg(not(target_os = "windows"))]
 fn test_rwlock_stdlib() {
+    use std::sync::RwLock;
     let rw = RwLock::new(0);
     {
         let _read_guard = rw.read().unwrap();