From fe83933b1d0ecbd06a6b7c0437471d0b99b8d16e Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Villemot?= <sebastien@dynare.org>
Date: Thu, 2 Mar 2023 15:55:51 +0100
Subject: [PATCH] Bugfix: undefined behaviour in
AbstractExternalFunctionNode::prepareForDerivation()
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Input and output ranges should not overlap when calling std::set_union(),
otherwise the behaviour is undefined.
It seems that in this precise case the computation would still be
correct (though inefficient), because of the properties of std::set or because
of the specific implementation in libstdc++. But it’s better to be on the safe
side.
---
src/ExprNode.cc | 14 +++++++++-----
1 file changed, 9 insertions(+), 5 deletions(-)
diff --git a/src/ExprNode.cc b/src/ExprNode.cc
index 09f40905..81ba65f4 100644
--- a/src/ExprNode.cc
+++ b/src/ExprNode.cc
@@ -6758,11 +6758,15 @@ AbstractExternalFunctionNode::prepareForDerivation()
non_null_derivatives = arguments.at(0)->non_null_derivatives;
for (int i = 1; i < static_cast<int>(arguments.size()); i++)
- set_union(non_null_derivatives.begin(),
- non_null_derivatives.end(),
- arguments.at(i)->non_null_derivatives.begin(),
- arguments.at(i)->non_null_derivatives.end(),
- inserter(non_null_derivatives, non_null_derivatives.begin()));
+ {
+ set<int> non_null_derivatives_tmp;
+ set_union(non_null_derivatives.begin(),
+ non_null_derivatives.end(),
+ arguments.at(i)->non_null_derivatives.begin(),
+ arguments.at(i)->non_null_derivatives.end(),
+ inserter(non_null_derivatives_tmp, non_null_derivatives_tmp.begin()));
+ non_null_derivatives = move(non_null_derivatives_tmp);
+ }
preparedForDerivation = true;
}
--
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