[clang] 2a1f306 - [clang][bytecode] Add more sanity checks for pointers used in `dynamic_cast` (#205070)

[via cfe-commits]

Author: Timm Baeder
Date: 2026-06-22T12:40:38+02:00
New Revision: 2a1f306515b67036a44b16e569a9f26f57520c54

URL: https://github.com/llvm/llvm-project/commit/2a1f306515b67036a44b16e569a9f26f57520c54
DIFF: https://github.com/llvm/llvm-project/commit/2a1f306515b67036a44b16e569a9f26f57520c54.diff

LOG: [clang][bytecode] Add more sanity checks for pointers used in `dynamic_cast` (#205070)

Make sure it's initialized and that it points to a record.

Added: 
    

Modified: 
    clang/lib/AST/ByteCode/Interp.cpp
    clang/test/AST/ByteCode/dynamic-cast.cpp

Removed: 
    


################################################################################
diff  --git a/clang/lib/AST/ByteCode/Interp.cpp b/clang/lib/AST/ByteCode/Interp.cpp
index b022d71ae1e49..106ca1b9e789e 100644
--- a/clang/lib/AST/ByteCode/Interp.cpp
+++ b/clang/lib/AST/ByteCode/Interp.cpp
@@ -2019,10 +2019,12 @@ bool DynamicCast(InterpState &S, CodePtr OpPC, const Type *DestTypePtr,
     return false;
   }
 
-  // TODO: Other checks?
-  if (!Ptr.isBlockPointer())
+  if (!Ptr.isBlockPointer() || !Ptr.getRecord())
     return false;
 
+  if (!Ptr.isInitialized())
+    return DiagnoseUninitialized(S, OpPC, Ptr, AK_Read);
+
   // Our given pointer, limited by the base that's currently being initialized,
   // if any.
   PtrView LimitedPtr;

diff  --git a/clang/test/AST/ByteCode/dynamic-cast.cpp b/clang/test/AST/ByteCode/dynamic-cast.cpp
index b782920eb8763..a40b455cecabf 100644
--- a/clang/test/AST/ByteCode/dynamic-cast.cpp
+++ b/clang/test/AST/ByteCode/dynamic-cast.cpp
@@ -294,3 +294,19 @@ namespace UnrelatedAndRootPtr{
   }
   static_assert(f());
 }
+
+namespace Invalid {
+  struct S { virtual void s(); };
+  struct A : S {};
+  struct B : A {};
+  constexpr __UINTPTR_TYPE__ g = 0;
+  static_assert(&dynamic_cast<A&>((S&)(B&)g) == &(A&)(B&)g); // both-error {{not an integral constant expression}} \
+                                                             // both-note {{cast that performs the conversions of a reinterpret_cast is not allowed in a constant expression}}
+
+  struct X : S { : ; }; // both-error {{expected expression}} \
+                        // both-error {{a type specifier is required for all declarations}}
+  constexpr X x; // both-error {{must be initialized by a constant expression}} \
+                 // both-note {{declared here}}
+  static_assert(&dynamic_cast<S&>((X&)x), ""); // both-error {{not an integral constant expression}} \
+                                               // both-note {{initializer of 'x' is not a constant expression}}
+}