[PATCH] D149061: [clang] remove dereferencing of invalid pointer

[Ashay Rane via Phabricator via llvm-commits]

ashay-github created this revision.
ashay-github added reviewers: nickdesaulniers, DavidSpickett, MaskRay, ayzhao.
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A line in the demangling code for float literals dereferences the
`.end()` iterator, which causes the Windows debug build of llvm-cxxfilt
to crash.  The failure can be reproduced by passing the string
`_Z5dummyIXtl8wrapper1IdEtlNS1_Ut_Edi9RightNametlNS2_Ut_ELd405ec00000000000EEEEEEvv`
to `llvm-cxxfilt -n`.

This patch rewrites the code to use the `.size()` member of the
string_view type to avoid dereferencing past the buffer.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D149061

Files:
  llvm/include/llvm/Demangle/ItaniumDemangle.h


Index: llvm/include/llvm/Demangle/ItaniumDemangle.h
===================================================================
--- llvm/include/llvm/Demangle/ItaniumDemangle.h
+++ llvm/include/llvm/Demangle/ItaniumDemangle.h
@@ -2331,11 +2331,9 @@
 
   void printLeft(OutputBuffer &OB) const override {
     const char *first = &*Contents.begin();
-    const char *last = &*Contents.end() + 1;
-
     const size_t N = FloatData<Float>::mangled_size;
-    if (static_cast<std::size_t>(last - first) > N) {
-      last = first + N;
+    if (Contents.size() >= N) {
+      const char *last = first + N;
       union {
         Float value;
         char buf[sizeof(Float)];


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