Merge #428

428: Fix Windows crash on caching compiled artifact. r=syrusakbary a=repi

Memory clone function wasn't able to write to new reserved memory object.

Changed so allocating Memory objects with protection flag allocates commited memory. And added unit test to verify that it doedsn't crash anymore.

Not fully sure this is the best solution though, but fixes this specific clone crash.

Co-authored-by: Johan Andersson <repi@repi.se>

lib/runtime-core/src/sys/windows/memory.rs

@@ -33,7 +33,13 @@ impl Memory {
 
         let protect = protection.to_protect_const();
 
-        let ptr = unsafe { VirtualAlloc(ptr::null_mut(), size, MEM_RESERVE, protect) };
+        let flags = if protection == Protect::None {
+            MEM_RESERVE
+        } else {
+            MEM_RESERVE | MEM_COMMIT
+        };
+
+        let ptr = unsafe { VirtualAlloc(ptr::null_mut(), size, flags, protect) };
 
         if ptr.is_null() {
             Err("unable to allocate memory".to_string())
@@ -229,3 +235,25 @@ fn round_up_to_page_size(size: usize, page_size: usize) -> usize {
 fn round_down_to_page_size(size: usize, page_size: usize) -> usize {
     size & !(page_size - 1)
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn clone() {
+        // these should work
+        let _ = Memory::with_size_protect(200_000, Protect::Read)
+            .unwrap()
+            .clone();
+        let _ = Memory::with_size_protect(200_000, Protect::ReadWrite)
+            .unwrap()
+            .clone();
+        let _ = Memory::with_size_protect(200_000, Protect::ReadExec)
+            .unwrap()
+            .clone();
+
+        // this would cause segmentation fault as uncommited memory with no access
+        //let _ = Memory::with_size_protect(200_000, Protect::None).unwrap().clone();
+    }
+}