[clang][bytecode] Fix a crash when redeclaring extern globals (#164204)

One iteration of this loop might've already fixed up the pointers of
coming globals, so check for that explicitly.

Fixes https://github.com/llvm/llvm-project/issues/164151

1 files changed, 4 insertions, 1 deletions

diff --git a/clang/lib/AST/ByteCode/Program.cpp b/clang/lib/AST/ByteCode/Program.cpp
index e653782..e0b2852 100644
--- a/clang/lib/AST/ByteCode/Program.cpp
+++ b/clang/lib/AST/ByteCode/Program.cpp
@@ -226,7 +226,10 @@ UnsignedOrNone Program::createGlobal(const ValueDecl *VD, const Expr *Init) {
         Globals[PIdx] = NewGlobal;
         // All pointers pointing to the previous extern decl now point to the
         // new decl.
-        RedeclBlock->movePointersTo(NewGlobal->block());
+        // A previous iteration might've already fixed up the pointers for this
+        // global.
+        if (RedeclBlock != NewGlobal->block())
+          RedeclBlock->movePointersTo(NewGlobal->block());
       }
     }
     PIdx = *Idx;