From 15630a4ddd6507bf0a01d339368020f4e3c71a1b Mon Sep 17 00:00:00 2001
From: Jean Perier <jperier@nvidia.com>
Date: Wed, 22 May 2019 08:26:50 -0700
Subject: [PATCH] [flang] Prevent possible infinte loop in parameter folding

Original-commit: flang-compiler/f18@38360930ce5b63987bc17fa235016743b90168ae
Reviewed-on: https://github.com/flang-compiler/f18/pull/469
Tree-same-pre-rewrite: false
---
 flang/lib/evaluate/fold.cc | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/flang/lib/evaluate/fold.cc b/flang/lib/evaluate/fold.cc
index 04bc338808ca..62c0da4fc692 100644
--- a/flang/lib/evaluate/fold.cc
+++ b/flang/lib/evaluate/fold.cc
@@ -806,6 +806,9 @@ static std::optional<Expr<T>> GetParameterValue(
           auto converted{ConvertToType(*dyType, common::Clone(*init))};
           semantics::ObjectEntityDetails *mutableObject{
               const_cast<semantics::ObjectEntityDetails *>(object)};
+          // Reset expression now to prevent infinite loops if the init
+          // expression depends on symbol itself.
+          mutableObject->set_init(std::nullopt);
           if (converted.has_value()) {
             *converted = Fold(context, std::move(*converted));
             auto *unwrapped{UnwrapExpr<Expr<T>>(*converted)};
@@ -827,7 +830,6 @@ static std::optional<Expr<T>> GetParameterValue(
                 "Initialization expression for PARAMETER '%s' (%s) cannot be converted to its type (%s)"_err_en_US,
                 symbol->name(), ss.str(), dyType->AsFortran());
           }
-          mutableObject->set_init(std::nullopt);
         }
       }
     }