ubsan: When diagnosing something wrong somewhere in memory, emit a note

pointing at the bad location and a snippet of nearby memory values. This is
strictly best-effort; reading these bytes to display the note could lead to a
seg fault, and that's explicitly OK.


git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@170415 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 21 insertions, 0 deletions

diff --git a/lib/ubsan/ubsan_type_hash.h b/lib/ubsan/ubsan_type_hash.h
index ac1be4944..dfaf32752 100644
--- a/lib/ubsan/ubsan_type_hash.h
+++ b/lib/ubsan/ubsan_type_hash.h
@@ -19,6 +19,27 @@ namespace __ubsan {
 
 typedef uptr HashValue;
 
+/// \brief Information about the dynamic type of an object (extracted from its
+/// vptr).
+class DynamicTypeInfo {
+  const char *MostDerivedTypeName;
+  sptr Offset;
+
+public:
+  DynamicTypeInfo(const char *MDTN, sptr Offset)
+    : MostDerivedTypeName(MDTN), Offset(Offset) {}
+
+  /// Determine whether the object had a valid dynamic type.
+  bool isValid() const { return MostDerivedTypeName; }
+  /// Get the name of the most-derived type of the object.
+  const char *getMostDerivedTypeName() const { return MostDerivedTypeName; }
+  /// Get the offset from the most-derived type to this base class.
+  sptr getOffset() const { return Offset; }
+};
+
+/// \brief Get information about the dynamic type of an object.
+DynamicTypeInfo getDynamicTypeInfo(void *Object);
+
 /// \brief Check whether the dynamic type of \p Object has a \p Type subobject
 /// at offset 0.
 /// \return \c true if the type matches, \c false if not.