[clang] cf8d4d4 - [clang][bytecode] Fix a crash in `CheckExtern()` (#174428)

[via cfe-commits]

Author: Timm Baeder
Date: 2026-01-06T07:49:32+01:00
New Revision: cf8d4d40698503bb20da4e5a576cc048524bc8eb

URL: https://github.com/llvm/llvm-project/commit/cf8d4d40698503bb20da4e5a576cc048524bc8eb
DIFF: https://github.com/llvm/llvm-project/commit/cf8d4d40698503bb20da4e5a576cc048524bc8eb.diff

LOG: [clang][bytecode] Fix a crash in `CheckExtern()` (#174428)

Check if the pointer field descriptor can be accessed at all before
calling `isInitialized()`, which relies on that.

Fixes https://github.com/llvm/llvm-project/issues/174382

Added: 
    

Modified: 
    clang/lib/AST/ByteCode/Interp.cpp
    clang/test/AST/ByteCode/typeid.cpp

Removed: 
    


################################################################################
diff  --git a/clang/lib/AST/ByteCode/Interp.cpp b/clang/lib/AST/ByteCode/Interp.cpp
index 966c9d9b5bf66..fe3069a4d8ef8 100644
--- a/clang/lib/AST/ByteCode/Interp.cpp
+++ b/clang/lib/AST/ByteCode/Interp.cpp
@@ -390,8 +390,9 @@ bool CheckExtern(InterpState &S, CodePtr OpPC, const Pointer &Ptr) {
   if (!Ptr.isExtern())
     return true;
 
-  if (Ptr.isInitialized() ||
-      (Ptr.getDeclDesc()->asVarDecl() == S.EvaluatingDecl))
+  if (!Ptr.isPastEnd() &&
+      (Ptr.isInitialized() ||
+       (Ptr.getDeclDesc()->asVarDecl() == S.EvaluatingDecl)))
     return true;
 
   if (S.checkingPotentialConstantExpression() && S.getLangOpts().CPlusPlus &&

diff  --git a/clang/test/AST/ByteCode/typeid.cpp b/clang/test/AST/ByteCode/typeid.cpp
index 7f282653e9a34..f529fb3b7a533 100644
--- a/clang/test/AST/ByteCode/typeid.cpp
+++ b/clang/test/AST/ByteCode/typeid.cpp
@@ -83,3 +83,13 @@ namespace GH173950 {
   // This used to crash with: Assertion `IsInitialized' failed in invokeDtor()
   const std::type_info &a_ti = typeid(a);
 }
+
+namespace MissingInitalizer {
+  struct Item {
+    const std::type_info &ti;
+  };
+  extern constexpr Item items[] = ; // both-error {{expected expression}} \
+                                    // both-note {{declared here}}
+  constexpr auto &x = items[0].ti; // both-error {{must be initialized by a constant expression}} \
+                                   // both-note {{initializer of 'items' is unknown}}
+}