[clang] [Clang] Fix stack-use-after-return in TryArrayCopy by allocating OpaqueValueExpr on the ASTContext (PR #192080)

[Oliver Hunt via cfe-commits]

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@@ -4380,10 +4380,10 @@ static void TryArrayCopy(Sema &S, const InitializationKind &Kind,
       InitializedEntity::InitializeElement(S.Context, 0, Entity);
   QualType InitEltT =
       S.Context.getAsArrayType(Initializer->getType())->getElementType();
-  OpaqueValueExpr OVE(Initializer->getExprLoc(), InitEltT,
-                      Initializer->getValueKind(),
-                      Initializer->getObjectKind());
-  Expr *OVEAsExpr = &OVE;
+  OpaqueValueExpr *OVE = new (S.Context) OpaqueValueExpr(
+      Initializer->getExprLoc(), InitEltT, Initializer->getValueKind(),
+      Initializer->getObjectKind());
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ojhunt wrote:

Yeah, it's a non-trivial amount of work, especially detecting the "don't end up in the AST" - because you could imagine an API where you do a trial evaluation or similar and say "ok this wasn't used" but the node got cached somewhere so it escaped. A true misery pit.

https://github.com/llvm/llvm-project/pull/192080