[clang] cebc4a1 - [Lex][Clang] Add checking to HeaderMapImpl::getString to make it more robust (#131677)

[via cfe-commits]

Author: Shafik Yaghmour
Date: 2025-03-20T08:17:11-07:00
New Revision: cebc4a167c518d83bb95fddd1c0dd6eebed3d505

URL: https://github.com/llvm/llvm-project/commit/cebc4a167c518d83bb95fddd1c0dd6eebed3d505
DIFF: https://github.com/llvm/llvm-project/commit/cebc4a167c518d83bb95fddd1c0dd6eebed3d505.diff

LOG: [Lex][Clang] Add checking to HeaderMapImpl::getString to make it more robust (#131677)

Static analysis identified the Len - 1 expression in
HeaderMapImpl::getString as problematic if Len is zero. After filing
this issue:

https://github.com/llvm/llvm-project/issues/130185

Indeed we should be checking MaxLen and verify it is not zero as well.

Fixes: https://github.com/llvm/llvm-project/issues/130185

Added: 
    

Modified: 
    clang/lib/Lex/HeaderMap.cpp

Removed: 
    


################################################################################
diff  --git a/clang/lib/Lex/HeaderMap.cpp b/clang/lib/Lex/HeaderMap.cpp
index 14731f29486c8..588b32ee9ca8e 100644
--- a/clang/lib/Lex/HeaderMap.cpp
+++ b/clang/lib/Lex/HeaderMap.cpp
@@ -155,6 +155,10 @@ std::optional<StringRef> HeaderMapImpl::getString(unsigned StrTabIdx) const {
 
   const char *Data = FileBuffer->getBufferStart() + StrTabIdx;
   unsigned MaxLen = FileBuffer->getBufferSize() - StrTabIdx;
+
+  if (MaxLen == 0)
+    return std::nullopt;
+
   unsigned Len = strnlen(Data, MaxLen);
 
   // Check whether the buffer is null-terminated.