[PATCH] D135192: Fix incorrect check for running out of source locations.

[Paul Pluzhnikov via Phabricator via cfe-commits]

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

Google ref: b/248613299


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D135192

Files:
  clang/lib/Basic/SourceManager.cpp


Index: clang/lib/Basic/SourceManager.cpp
===================================================================
--- clang/lib/Basic/SourceManager.cpp
+++ clang/lib/Basic/SourceManager.cpp
@@ -455,8 +455,10 @@
                                          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;


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