[clang] fccabca - [clang][bytecode] Protect against invalid C++26 string repr (#213639)

[via cfe-commits]

Author: Timm Baeder
Date: 2026-08-03T14:46:27+02:00
New Revision: fccabca20c732cc93b018effa7381e2e2a6f9506

URL: https://github.com/llvm/llvm-project/commit/fccabca20c732cc93b018effa7381e2e2a6f9506
DIFF: https://github.com/llvm/llvm-project/commit/fccabca20c732cc93b018effa7381e2e2a6f9506.diff

LOG: [clang][bytecode] Protect against invalid C++26 string repr (#213639)

We can't call `getNumElems()` for unknown-size arrays.

Added: 
    

Modified: 
    clang/lib/AST/ByteCode/Context.cpp
    clang/test/AST/ByteCode/cxx26.cpp

Removed: 
    


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diff  --git a/clang/lib/AST/ByteCode/Context.cpp b/clang/lib/AST/ByteCode/Context.cpp
index b913d2a9f539c..9f1d9b899052d 100644
--- a/clang/lib/AST/ByteCode/Context.cpp
+++ b/clang/lib/AST/ByteCode/Context.cpp
@@ -208,7 +208,8 @@ bool Context::evaluateStringRepr(State &Parent, const Expr *SizeExpr,
       return false;
     }
 
-    if (!Ptr.isLive() || !Ptr.getFieldDesc()->isPrimitiveArray())
+    if (!Ptr.isLive() || !Ptr.isInitialized() || Ptr.isUnknownSizeArray() ||
+        !Ptr.getFieldDesc()->isPrimitiveArray())
       return false;
 
     // Must be char.

diff  --git a/clang/test/AST/ByteCode/cxx26.cpp b/clang/test/AST/ByteCode/cxx26.cpp
index 769deb28cdf50..9dc6270b9d551 100644
--- a/clang/test/AST/ByteCode/cxx26.cpp
+++ b/clang/test/AST/ByteCode/cxx26.cpp
@@ -91,3 +91,15 @@ namespace ConstexprUnknownReference {
   }
 
 }
+
+namespace UnknownSizeArrayString {
+  constexpr const char foo[] = {bar}; // both-error {{use of undeclared identifier}} \
+                                      // ref-note {{declared here}}
+  struct S {
+    constexpr int size() const { return 4; }
+    constexpr const char *data() const { return foo; }
+  };
+  static_assert(false, S{}); // both-error {{the message in a static assertion must be produced by a constant expression}} \
+                             // ref-note {{initializer of 'foo' is unknown}} \
+                             // both-error {{static assertion failed}}
+}