Fix incorrect check for running out of source locations.

When CurrentLoadedOffset is less than TotalSize, current code will
trigger unsigned overflow and will not return an "allocation failed"
indicator.

Google ref: b/248613299

Reviewed By: dblaikie

Differential Revision: https://reviews.llvm.org/D135192

diff --git a/clang/lib/Basic/SourceManager.cpp b/clang/lib/Basic/SourceManager.cpp
index 6aae581..20bb594 100644 (file)
--- a/clang/lib/Basic/SourceManager.cpp
+++ b/clang/lib/Basic/SourceManager.cpp
@@ -454,8 +454,10 @@ SourceManager::AllocateLoadedSLocEntries(unsigned NumSLocEntries,
                                          SourceLocation::UIntTy TotalSize) {
   assert(ExternalSLocEntries && "Don't have an external sloc source");
   // Make sure we're not about to run out of source locations.
-  if (CurrentLoadedOffset - TotalSize < NextLocalOffset)
+  if (CurrentLoadedOffset < TotalSize ||
+      CurrentLoadedOffset - TotalSize < NextLocalOffset) {
     return std::make_pair(0, 0);
+  }
   LoadedSLocEntryTable.resize(LoadedSLocEntryTable.size() + NumSLocEntries);
   SLocEntryLoaded.resize(LoadedSLocEntryTable.size());
   CurrentLoadedOffset -= TotalSize;