Fix unsigned integer overflow (#1299)

Summary:
## Changes in this pull request

Issue fixed: #

### Checklist

- [ ] All tests pass. Demo project builds and runs.
- [ ] I added tests, an experiment, or detailed why my change isn't tested.
- [ ] I added an entry to the `CHANGELOG.md` for any breaking changes, enhancements, or bug fixes.
- [ ] I have reviewed the [contributing guide](https://github.com/Instagram/IGListKit/blob/master/.github/CONTRIBUTING.md)
Pull Request resolved: #1299

Reviewed By: m3rlin45

Differential Revision: D18703628

Pulled By: TimOliver

fbshipit-source-id: d347ed9c59c62ccdb73bd3abd14e289b7c06f3f6

CHANGELOG.md

@@ -108,6 +108,8 @@ The changelog for `IGListKit`. Also see the [releases](https://github.com/instag
 
 - Request the `UICollectionView` until just-before we update. This way if the `UICollectionView` is changed between update-queue and execution, we guarantee the update is performed on the correct view. Ship with experiment `IGListExperimentGetCollectionViewAtUpdate` from Ryan Nystrom. [Maxime Ollivier](https://github.com/maxolls) (tbd)
 
+- Fixed unsigned integer overflow handling in `IGListBatchUpdateData` [Jason Hsu](https://github.com/tuoxie007) [(#1299)](https://github.com/Instagram/IGListKit/pull/1299)
+
 4.0.0
 -----
 ### Breaking Changes

Source/IGListDiffKit/IGListBatchUpdateData.mm

@@ -38,6 +38,9 @@ + (void)_cleanIndexPathsWithMap:(const std::unordered_map<NSInteger, IGListMoveI
                     indexPaths:(NSMutableArray<NSIndexPath *> *)indexPaths
                        deletes:(NSMutableIndexSet *)deletes
                        inserts:(NSMutableIndexSet *)inserts {
+    if (indexPaths.count == 0) {
+        return;
+    }
     for (NSInteger i = indexPaths.count - 1; i >= 0; i--) {
         NSIndexPath *path = indexPaths[i];
         const auto it = map.find(path.section);
@@ -77,8 +80,8 @@ - (instancetype)initWithInsertSections:(nonnull NSIndexSet *)insertSections
         // convert one of the item changes into a section delete+insert. this will fail hard and be VERY difficult to
         // debug
         const NSInteger moveCount = [moveSections count];
-        std::unordered_map<NSInteger, IGListMoveIndex*> fromMap(moveCount);
-        std::unordered_map<NSInteger, IGListMoveIndex*> toMap(moveCount);
+        std::unordered_map<NSInteger, IGListMoveIndex*> fromMap(MAX(moveCount, 1));
+        std::unordered_map<NSInteger, IGListMoveIndex*> toMap(MAX(moveCount, 1));
         for (IGListMoveIndex *move in moveSections) {
             const NSInteger from = move.from;
             const NSInteger to = move.to;

Source/IGListKit/Internal/IGListWorkingRangeHandler.mm

@@ -121,7 +121,7 @@ - (void)_updateWorkingRangesWithListAdapter:(IGListAdapter *)listAdapter {
     }
 
     // Build the current set of working range section controllers
-    _IGListWorkingRangeSectionControllerSet workingRangeSectionControllers (visibleSectionSet.size());
+    _IGListWorkingRangeSectionControllerSet workingRangeSectionControllers (MAX(visibleSectionSet.size(), 1));
     for (NSInteger idx = start; idx < end; idx++) {
         id item = [listAdapter objectAtSection:idx];
         IGListSectionController *sectionController = [listAdapter sectionControllerForObject:item];