[io/watcher] Fix crash in file event watcher functionality on Windows.

It is possible to get '-1' bytes reported as available. This change ensures that only positive number of available bytes are being read. Fixes #40348 Change-Id: I9f76bd7ca725c9e48ae5a9c44a25d3c12a487194 Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/164340 Reviewed-by: Siva Annamalai <[email protected]> Commit-Queue: Alexander Aprelev <[email protected]>
dart-lang · Sep 24, 2020 · 08c3276 · 08c3276
1 parent 7ec28c3
commit 08c3276
Showing 1 changed file with 3 additions and 0 deletions.
diff --git a/runtime/bin/file_system_watcher_win.cc b/runtime/bin/file_system_watcher_win.cc
@@ -80,6 +80,9 @@ Dart_Handle FileSystemWatcher::ReadEvents(intptr_t id, intptr_t path_id) {
   const intptr_t kEventSize = sizeof(FILE_NOTIFY_INFORMATION);
   DirectoryWatchHandle* dir = reinterpret_cast<DirectoryWatchHandle*>(path_id);
   intptr_t available = dir->Available();
+  if (available <= 0) {
+    return Dart_NewList(0);
+  }
   intptr_t max_count = available / kEventSize + 1;
   Dart_Handle events = Dart_NewList(max_count);
   uint8_t* buffer = Dart_ScopeAllocate(available);