[clang] 51b54ff - [clang][bytecode] Fix discarded dynamic casts (#200723)

[via cfe-commits]

Author: Timm Baeder
Date: 2026-06-01T10:41:01+02:00
New Revision: 51b54fffee8c4b3440a03b3affceba3690754115

URL: https://github.com/llvm/llvm-project/commit/51b54fffee8c4b3440a03b3affceba3690754115
DIFF: https://github.com/llvm/llvm-project/commit/51b54fffee8c4b3440a03b3affceba3690754115.diff

LOG: [clang][bytecode] Fix discarded dynamic casts (#200723)

If they are checked.

Added: 
    

Modified: 
    clang/lib/AST/ByteCode/Compiler.cpp
    clang/test/AST/ByteCode/cxx23.cpp

Removed: 
    


################################################################################
diff  --git a/clang/lib/AST/ByteCode/Compiler.cpp b/clang/lib/AST/ByteCode/Compiler.cpp
index 774a853950837..322c1f827223b 100644
--- a/clang/lib/AST/ByteCode/Compiler.cpp
+++ b/clang/lib/AST/ByteCode/Compiler.cpp
@@ -3570,6 +3570,8 @@ bool Compiler<Emitter>::VisitCXXDynamicCastExpr(const CXXDynamicCastExpr *E) {
   if (!this->emitCheckDynamicCast(E))
     return false;
 
+  if (DiscardResult)
+    return this->emitPopPtr(E);
   return true;
 }
 

diff  --git a/clang/test/AST/ByteCode/cxx23.cpp b/clang/test/AST/ByteCode/cxx23.cpp
index 7b2d1c6e7e1e1..4619023af83e6 100644
--- a/clang/test/AST/ByteCode/cxx23.cpp
+++ b/clang/test/AST/ByteCode/cxx23.cpp
@@ -641,4 +641,8 @@ namespace DynamicCast {
                                                   // all23-note {{dynamic_cast applied to object 'a' whose dynamic type is not constant}} \
                                                   // all20-note {{function parameter 'a' with unknown value cannot be used in a constant expression}}
   }
+
+  struct S {};
+  constexpr S s;
+  constexpr int foo = (dynamic_cast<const S &>(s), 0);
 }