[clang] 7446601 - [-Wunsafe-buffer-usage] Fix a potential overflow bug reported by #126334 (#129169)

[via cfe-commits]

Author: Ziqing Luo
Date: 2025-02-28T10:33:32-08:00
New Revision: 7446601c6a9b71945fdc9d7434d8347789708858

URL: https://github.com/llvm/llvm-project/commit/7446601c6a9b71945fdc9d7434d8347789708858
DIFF: https://github.com/llvm/llvm-project/commit/7446601c6a9b71945fdc9d7434d8347789708858.diff

LOG: [-Wunsafe-buffer-usage] Fix a potential overflow bug reported by #126334 (#129169)

`MeasureTokenLength` may return an unsigned 0 representing failure in
obtaining length of a token. The analysis now gives up on such cases.
Otherwise, there might be issues caused by unsigned integer "overflow".

Added: 
    

Modified: 
    clang/lib/Analysis/UnsafeBufferUsage.cpp

Removed: 
    


################################################################################
diff  --git a/clang/lib/Analysis/UnsafeBufferUsage.cpp b/clang/lib/Analysis/UnsafeBufferUsage.cpp
index ff4f940a596e3..12e99143cb148 100644
--- a/clang/lib/Analysis/UnsafeBufferUsage.cpp
+++ b/clang/lib/Analysis/UnsafeBufferUsage.cpp
@@ -2364,12 +2364,13 @@ template <typename NodeTy>
 static std::optional<SourceLocation>
 getEndCharLoc(const NodeTy *Node, const SourceManager &SM,
               const LangOptions &LangOpts) {
-  unsigned TkLen = Lexer::MeasureTokenLength(Node->getEndLoc(), SM, LangOpts);
-  SourceLocation Loc = Node->getEndLoc().getLocWithOffset(TkLen - 1);
-
-  if (Loc.isValid())
-    return Loc;
+  if (unsigned TkLen =
+          Lexer::MeasureTokenLength(Node->getEndLoc(), SM, LangOpts)) {
+    SourceLocation Loc = Node->getEndLoc().getLocWithOffset(TkLen - 1);
 
+    if (Loc.isValid())
+      return Loc;
+  }
   return std::nullopt;
 }