Ensure fibers get guard pages on Windows

rayon-core/src/fiber/mod.rs

@@ -488,7 +488,9 @@ impl WinFiber {
 
     fn new(stack_size: usize) -> Option<Self> {
         unsafe {
-            let fiber = kernel32::CreateFiber(stack_size as _,
+            let fiber = kernel32::CreateFiberEx(0x1000,
+                stack_size as _,
+                0,
                 Some(fiber_proc),
                 0i32 as _);
             if fiber == 0i32 as _ {
@@ -510,6 +512,14 @@ impl Drop for WinFiber {
 
 #[cfg(windows)]
 unsafe extern "system" fn fiber_proc(_: winapi::LPVOID) {
+    #[cfg(debug_assertions)] {
+        let mut stack_low = 0;
+        let mut stack_high = 0;
+        kernel32::GetCurrentThreadStackLimits(&mut stack_low, &mut stack_high);
+        let mut mbi = mem::zeroed();
+        assert!(kernel32::VirtualQuery(stack_low as _, &mut mbi, 0x1000) == 0);
+    }
+
     let worker = &*WorkerThread::current();
     loop {
         let data = NEW_FIBER_DATA.with(|fiber_data| fiber_data.take());