[llvm] [llvm][mustache] Fix UB in ASTNode::render() (PR #142249)

[Nikita Popov via llvm-commits]

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@@ -560,68 +566,71 @@ void toMustacheString(const json::Value &Data, raw_ostream &OS) {
   }
 }
 
-void ASTNode::render(const json::Value &Data, raw_ostream &OS) {
-  ParentContext = &Data;
+void ASTNode::render(const json::Value &CurrentCtx, raw_ostream &OS) {
+  // Set the parent context to the incoming context so that we
+  // can walk up the context tree correctly in findContext().
+  ParentContext = &CurrentCtx;
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nikic wrote:

Not related to your change, but seeing this, I wonder why we don't also have to reset ParentContext to the original value when leaving the recursion?

https://github.com/llvm/llvm-project/pull/142249